Ask Slashdot: How Do You Build Your Own Vacuum Tubes?

Could you beat wireless headphones by creating your own DIY home audio system? Two weeks ago one Slashdot commenter argued, "to have good audio that is truly yours and something to be proud of, you need to make your own vacuum tube amplifier and then use it to power real electrostatic headphones over a wire." And now long-time Slashdot reader mallyn is stepping up to the challenge: I want to try to make my own vacuum tubes. Is there anyone here who has tried DIY vacuum tubes (or valves, to you Europeans)? I need help getting started -- how to put together the vacuum plumbing system; how to make a glass lathe; what metals to use for the elements (grid, plate, etc). If this is not the correct forum, can anyone please gently shove me into the correct direction? It needs to be online as my physical location (Bellingham, Washington) is too far away from the university labs where this type of work is likely to be done.
Slashdot's covered the "tubes vs. transistors" debate before, but has anyone actually tried to homebrew their own? Leave your best answers in the comments. How do you build your own vacuum tubes?

Comments

Covered in the past.

[Pikoro]

Here's a good one with links to more: http://hackaday.com/2016/05/04...

Re:Covered in the past.

[Pikoro]

And here's another: http://hackaday.com/2014/11/21...

Re:Covered in the past.

[dennis612b]

Lots of hits on DIY vacuum tubes and they don't need to be made entirely from glass to work.

Re:Covered in the past.

[arglebargle_xiv]

You don't even need vacuum tubes/valves, just build a valve sound simulator and you can get all the distortion and noise of the genuine tube/valve sound without any of the heat, fragility, and power consumption. It's a win/win situation.

Re:Covered in the past.

[zwarte piet]

It's an interesting idea, but do you really need a box with analog stuff for that? I bet the same can be done in software and then you can make profiles for different kinds of tube amps and tweak it to your own taste.

Re: Covered in the past.

[Anonymous Coward]

A whole industry exists to bring "tube warmth" to digital audio via plug-ins. Waves, Universal Audio and Steven Slate Designs are some of the bigger names.

Re:Covered in the past.

[gordguide]

You don't even need vacuum tubes/valves, just build a valve sound simulator and you can get all the distortion and noise of the genuine tube/valve sound without any of the heat, fragility, and power consumption. It's a win/win situation.

They do throw some heat, they are far from fragile (otherwise every aircraft flight would be a throw of the dice, as there is no solid-state means of creating radar) and they use power because they are most often used in high-power applications where transistors simply cannot survive, even briefly (like, say, radar, terrestrial broadcasting, your microwave oven, and so on).

I am quite familiar with the digital simulations of vacuum tube audio sonics and tone, and the best they can do is come close. In no way do they sound exactly the same as a real-world vacuum tube circuit, which is why such devices still exist. They can emulate the sound in an mp3-kind of fidelity though, and generally they can only mimic the most eggrarious distortion modes of a tube driven circuit ... kind of like how TV Soap Opera Set colour mimics what you see with your eyes if you look around the room.

No no no.

[fyngyrz]

You don't need vacuum tubes. That's such a horrible audio myth. They glow in the dark and look nice. Aside from that, they produce more distortion, more noise, use more power, are more fragile, and have shorter lifetimes than solid state electronics. They do not sound better, given $X spent on whatever, presuming some reasonable amount of tech is returned per dollar.

OTOH, if you just want to make vacuum tubes because.... you want to make vacuum tunes... have at it :)

Re:No no no.

[Anonymous Coward]

The reason real guitarists prefer tubes is because of the distortion. Solid state just doesn't compare.

Re:No no no.

[Anonymous Coward]

But but but... you obviously haven't listened to hand crafted artisanal vacuum tubes using hand blown glass and mastodon hair wrapped with isometrically pure tungsten. The tungsten caresses the electrons in a way that's just not possible modern day transistors.

Re:No no no.

[DewDude]

they produce more distortion

Only in circuits where they are driven extremely hard...or guitar amps where a tube will naturally do what takes ton of DSP

more noise

again...depends on what type of circuit you're using and if you're using the suitable tube. Stick a 6AU6 in your audio stage and it's going to get noisy.

use more power

You have me here. Thermionic Emission requires the heat.

are more fragile

Toss-Up. Drop a tube and it'll likely break depending how and what it hits. On the flipside; there are ways a transistor will fail that a tube won't care about. My tubes aren't going to care about a voltage surge or a few extra volts in the circuit. A solid state transistor will freak out if the voltage drops below a specific threshold in relation to the rest of it's voltages and will just give up during things like power surges or EMPs.

and have shorter lifetimes than solid state electronics.

Again...not entirely true. I know some tube equipment with original tubes that outlasted solid-state replacement units.

They do not sound better

You cannot measure or quantify sound quality.

Re:No no no.

[KingOfBLASH]

Actually that's not true, just ask a guitarist (and IAAG - I Am A Guitarist!)

Vacuum tubes create a noisy signal, but in a weird coincidence, they do it in a way that is pleasing to the ear. The clipping and distortion sounds "warm," and there's an added depth in the sound (harmonics) that you don't get via transistors -- unless you create circuits that mimic the behavior of a vacuum tube.

Metallica? Tube amps. John Mayer? Tube Amps. Clapton? Tube amps. BB King? Tube amps. Eric Johnson? Steve Vai? Garth Brooks? All tube amps.

Of course, much of the "tone" we guitarists revere comes from overdriven and abused guitar tubes -- cranking up the volume on the tube so that there's massive distortion and noise -- which again sounds pleasing to some people.

Now, it's one thing to overdrive a tube or change the bias on it to get a particular sound from your guitar, what about building a tube amp to just listen to music?

Well, I suspect this is essentially "remixing" songs. Adding a bit more depth, dirt, or warmth (from the noisy tube) might sound better but that's subjective, and it's all about personal preference.

So, sir, you might argue that you dislike what a noisy tube does to your signal, but you can't say some people won't perceive it as improved, as it's about personal taste.

Re:No no no.

[Anonymous Coward]

So they waste your money sticking vacuum tubes in the circuit, then use solid state amps in the actual headphones. I'll stick with my original Koss ESP-9 electrostatics - they've stood the test of time without the vacuum tubes raising from the interior gimmick.

Re:No no no.

[Third Position]

Not true. Breakup characteristics are measurably different between tubes and transistors.

Re:No no no.

[Anonymous Coward]

Spoken as someone who knows a little, but not enough about music engineering.

Tubes have been and are still used for ALL manner of instruments (including vocal) for "warming" sounds, saturation and creating distortion effects. The even harmonic distortion they produce when you overdrive are pleasing to the ear and can add an organic character to a recording that is otherwise lacking.
Different tubes produce different sounds so experimenting with your own would be interesting. For example: I remember replacing the 12V tube in my marshal amp with a recommended one to create more clear note definition when distorted - the results were pleasing and less muddy. (to me, remember this is a highly subjective area)

In music it is quite often the IMPRECISION that makes the bland great.

Long before we had the ability to simulate this electronically the only method to achieve this. In recent years however the simulated electronic solutions have come light years and it would be VERY hard for anyone to tell the difference between an analogue and digital tube distortion effect in a blind test.

So my advice would be twofold based on the questions:
1) Is doing this as a hardware project the point or just sound quality?
If the former, see point 2. If the latter then investigate the plethora of apps/plugins that simulate this.
While most are designed as VST (or other) plugins for DAWs, some of the best ones also have stand alone desktop app versions. You will get MUCH more variation to play with and in minutes rather than weeks.
e.g. http://www.ikmultimedia.com/products/amplitube4/

2) Why are you building your own tubes when they are cheap as chips and come in many flavors already?
If to experiment with different tube styles, go nuts.
If to simply increase sound quality, do yourself a favor and buy one or more as they are cheap. You could go a step further and buy tube DI boxes also which will do what you want out of the box.

Re:No no no.

[Anonymous Coward]

You cannot measure or quantify sound quality.

Yes you can. Hi-Fi equipment is suppose to *reproduce* the original as accurately as possible. This is something you can and people do measure. Hence the name Hi-Fi an abbreviation of High Fidelity.

Re:No no no.

[Khyber]

"and have shorter lifetimes than solid state electronics."

Spoken like someone that never used W-grade (military) tubes in their life. Mine are still kicking in my 1978 Fender Super Reverb, from when my father bought them. That's almost 40 years. You got any solid state stuff that old, gramps?

Re:No no no.

[somenickname]

You don't need vacuum tubes. That's such a horrible audio myth

The summary doesn't say anything about sound quality. My guess is that he's using vacuum tubes because it's possible to 100% DIY a vacuum tube amplifier from off the shelf parts. If you try to build a solid state amp from scratch, you are probably going to need to get custom PCBs built and you'll get to test the steadiness of your hands as you try to solder tiny SMD chips.

Now, making the actual tubes seems a little overkill (is he also making his own transformers, resistors, wiring, etc?) but, if you want to build your own amplifier from scratch, tubes is the way to go.

Re: No no no.

[sg_oneill]

Vacuum tubes don't necessarily sound more accurate , but unless you run a recording studio you don't necessarily want accurate , which is why studio monitors don't necessarily make for good listening speakers. Valves however sound good and that's a result of their behaviour at high current. Transistor amplification hard clips at max power creating flat peaks that sound absolutely terrible, whereas Valves produce rounded clips with a degree of compression at the peaks. This has the psychoacoustic effect of sounding "warm". This isn't a myth , you can see precisely this effect on a CRO. To put it slightly clumsily , transistors distort when ran out of spec whilst valves saturate

Re:No no no.

[thegarbz]

You're conflating two different purposes for an amplifier. An instrument amplifier is part of the instrument itself. The choice of that amplifier has a significance to the music that is trying to be produced. Implying that all those famous guitarists chose tube amps because they are better at something ignores all the solid state amps that are used by musicians too. They have a different sound, not good, not bad, just different. Both when run normally and when overdriven. The choice of an instrument amplifier is purely artistic.

Well, I suspect this is essentially "remixing" songs. Adding a bit more depth, dirt, or warmth (from the noisy tube) might sound better but that's subjective, and it's all about personal preference.

This irks me. It's like saying that the Mona Lisa is nice and all but it should have been painted with more yellow. The purpose of a hifi amplifier is to reproduce the small signal as faithfully as possible, and with as little distortion as possible. Every design aspect should be based on the output being nothing more than a larger input, any modification to the signal should have happened before this stage (either in the studio, or if you really feel like not listening to the music as the musician intended then with a pre-amp). In that regard an interesting combination is often a vacuum preamp followed by a solid state tube amp.

But really the parent was on the money with the physics behind it. Tubes produce a more pleasing sound than a typical Class AB push pull amplifier due to harmonic distortion being predominantly odd order rather than the even order in solid state amplifiers. However in terms of being able to faithfully reproduce a signal in a larger form they are blown away in every metric (except power consumption, the GP got that wrong) buy a well designed Class A solid-state amplifier.

Now personally I think the Mona Lisa is too small.

Re:No no no.

[thegarbz]

I got that backwards. Tubes produce even-order distortion. Push-pull solid state amplifiers have almost zero even order distortion.

Read twice, post once.

Re:No no no.

[thegarbz]

Instrument is the right word. But there's a key theory in your post:

In music it is quite often the IMPRECISION that makes the bland great.

That imprecision is an artistic choice. It should not be a listener's choice. The imprecision of instrument amplifiers are part of the instrument. The goal of a normal stereo amplifier should be the most precise reproduction of the artist's choices.

But I'm probably in the minority with this view given how many times I step into a hired car and find the first thing I need to do is drop the bass and treble back down to zero.

Re:No no no.

[Bruce Perens]

Just think of it as even harmonics, and it fits better into musical theory.

Obviously, what you really want to do is use amplifiers with sufficient power that they are never driven into distortion. And if you want distortion, get it from an effects pedal.

Re:No no no.

[Bruce Perens]

Of course, modern solid state amplifiers aren't particularly power limited (at least if you have the cash) and should never be driven into distortion. Effects pedals give you whatever distortion you want and have the advantage that you can turn the amplifier some level other than 11 and you still have the distortion you like.

Re:No no no.

[Bruce Perens]

This is better stated as "most people don't know what good sound reproduction actually sounds like". We certainly can measure sound quality. People like Amar Bose didn't ever publish specifications because the average listener prefers unreal bass (go listen to a live orchestra) and isn't too sensitive to distortion.

It gets worse with digital. We took a medium that could reproduce sound much better, and compressed it, taking away that advantage. All musical compression is designed to replace aliasing with noise because that is easier for the listener perceptually, so it all hisses and sizzles.

Re:No no no.

[Bruce Perens]

Doesn't matter. No modern amplifier has to be driven into distortion. We've got all of the power you need.

Re:No no no.

[Bruce Perens]

You're not using the original capacitors, are you? If so, some time with an ESR meter and the required replacements would help.

Yes, I definitely have solid-state electronics that old. Including test equipment. But most have been recapped.

Re:No no no.

[ChrisMaple]

Because tubes have to heat the cathode in order to eject electrons, at audio frequencies the best tubes are inherently more noisy than the best transistors. It's not a lot of noise - in a properly designed circuit it's unlikely to be noticeable - but physics does not allow a tube at audio frequencies to be as quiet as a transistor.

Re:No no no.

[ChrisMaple]

Are you referring to dynamic range compression or data compression?

Re:No no no.

[TechyImmigrant]

The reason real guitarists prefer tubes is because of the distortion. Solid state just doesn't compare.

Well these days they do compare. Humans can't distinguish between an amp modeled on (for example) a Kemper modeling amp and the tube amp it modeled.
A few years ago it was not the case, but DSP always wins in the end.

Re:No no no.

[KingOfBLASH]

This irks me. It's like saying that the Mona Lisa is nice and all but it should have been painted with more yellow.

::SNIP::

Now personally I think the Mona Lisa is too small.

The way art is presented (whether that's music through a hi fi stereo or a painting to the public) can change the way the art itself is perceived.

You might have no control over how much yellow Leonardo used for Mona, or how big he painted her, but you might put her under fluorescent or halogen lamps, or in sunlight (which will all add slightly different color casts to the painting). You might choose to display her behind a fresnel lens to make her bigger. Or you might put her on a white wall, or a black wall, or opposite a red accent wall. Or when printing a copy, you might choose a specific color gamut.

And each choice will alter how the viewer sees her.

Music is the same. You might prefer a solid state hi fi stereo, with a level equalizer Others will prefer to listen to beats headphones with the bass cranked up. Others will prefer vinyl through a tube amp.

Each individual adds to art by their choice of presentation. Don't hate if someone has different preferences, because in the end, it's a personal matter not a matter of fact. Which is why you shouldn't use absolutes and say tube hi fis are rubbish.

Re:No no no.

[wierd_w]

Sure you can, unless you believe in magic.

If the output waveforms are the same when plotted on an oscilloscope, then there is no difference between the amplifiers as far as sound quality is concerned.

Re:No no no.

[ChrisMaple]

Having done both, it's much easier to build a solid state amp than a tube amp from scratch. Neither requires a PCB, but tubes almost always have to be socketed and usually need a chassis. If the signal level is low. the filament voltage either needs to be DC or needs to be shielded from the signal path. Transistors and ICs don't have filaments. ICs provide more gain per stage, and a power amp can be made with just 1 or 2 ICs, depending on the gain required. Tube amps require an output transformer. Tubes use much higher voltages, increasing the risk of painful or deadly shocks.

Re:No no no.

[Skeptical1]

This needs to be cleared up. There's a difference between what musicians do (i.e sound production) and what a HiFi system is supposed to do (i.e. sound RE-production. In the former case, I don't care if you glue Canadian pennies *1974 preferred* to your guitar strings - if you like the sound - you've succeeded. In the latter case, If you want what to maintain what the artist was trying to achieve you need the most linear system you can find AND not overdrive it or you'll just be distorting the distortion that they were after.

Re:No no no.

[BlueStrat]

Of course, modern solid state amplifiers aren't particularly power limited (at least if you have the cash) and should never be driven into distortion. Effects pedals give you whatever distortion you want and have the advantage that you can turn the amplifier some level other than 11 and you still have the distortion you like.

As a pro-level guitarist for 4+ decades and who also has been designing & building tube guitar amplifiers for nearly as long, I have to disagree.

Distortion type effects pedals are attempts to imitate what goes on in a tube guitar amplifier being pushed to (and past) it's limits and some come close (and many more close enough for the average local artist/band in bar/small-gig venues) but it does not sound nor 'feel' the same to play through for a good guitar player.

Nearly all the flagship lines of the major guitar amplifier manufacturers are tube amps. Most pro-level concert/festival guitar amplifier backlines are tube amplifiers. Fender Twin Reverbs, Super Reverbs, and Marshall amplifiers (often vintage '60s/'70s era) are the vast majority of venue-owned backline kit provided for touring acts (and usually specified by the artist/band in the performance contract 'riders' section) at most large venues.

As to making a home-brew vacuum tube, it is doable but not practical. To get predictable performance mechanical tolerances must be exacting and the materials used in commercial tubes are rather exotic and difficult (if not impossible to come close to) for a home-brew vacuum tube maker. What you end up doing is making a tube using 'best guesses' and test/measure the tube's operational parameters and design the circuit around those parameters, rather than the other way around.

The other problem with the inability to make tubes with fairly consistent and predictable performance and operational parameters is that it makes building things like the typical push-pull 2 or 4 tube Class AB1/AB2 power amplifier extremely difficult, as the tubes must be fairly close in there operational parameters or the unbalanced circuit will likely destroy the tube(s) of one side that conduct the most current. It would also be necessary to custom-wind output transformers to whatever plate impedance the tube(s) happened to exhibit

If you love vacuum tubes and spending exorbitant amounts of time & money mucking about with molten glass and exotic metals for fun, have at it. Just don't expect to build the equivalent of a McIntosh MC30 or a 100-watt Marshall using them.

There is an amazing amount of exacting engineering, sophisticated manufacturing processes/techniques, and exotic materials science in the old commercial vacuum tubes even by today's standards and is pretty much impractical and beyond the means for the vast majority of private experimenters to reproduce in a home shop.

Strat

Re:No no no.

[jenningsthecat]

... they produce more distortion... They do not sound better, given $X spent on whatever, presuming some reasonable amount of tech is returned per dollar.

This is simply not true; in fact, it's a line of BS almost as bad as the one that says thousand dollar cables will make your system sound magical. (BTW, something you hear is not necessarily true just because it's said by a bunch of engineers bathed in the fountain of 'knowledge' passed on by an earlier generation of engineers whose conclusions were 'helped' by marketing requirements).

First, let's look at the metric known as THD; it is calculated as the ratio between the total power of all harmonics and the power of the fundamental. It assumes that all harmonics are equal in their detrimental effects on the final sound. However, we've known since the 50's that: 1) odd-order harmonics are more audible, and more objectionable, than even-order harmonics; 2) audibility and objectionability of harmonics increases as the order increases. In fact, the best audio engineers of the day, (such as the BBC's D.E.L. Shorter), proposed that THD be calculated based on the square, or even the cube, of the order of the harmonic. They were overruled, probably because the amplifier manufacturers of the day had turned to push-pull pentode designs with lots of NFB; these had many more odd-order and high-order harmonics than earlier triode designs, and the unweighted THD calcs made them look better on paper.

Why does this matter? Well, first, negative feedback obtains lower THD figures at the expense of creating more high-order harmonics - the total power in the harmonics is decreased, but the number of measurable harmonics, (and they, or at least their effects, are audible, as it turns out), increases. Second, negative feedback can increase the number of odd-order harmonics, depending on the feedback scheme and the amplifier topology. What does this have to do with tube VS transistor? In short, triode vacuum tubes, (the 'triode' part is important), have far greater intrinsic linearity than any semiconductor device. (Intrinsic linearity is a measure of the device's distortion in a circuit that has no negative feedback). The best directly heated triode power amplifiers can obtain percent THD figures in the low single-digits without the use of any negative feedback. That means that they can avoid excessive odd-order and higher-order harmonics to an extent that no transistor amplifier can - transistor amps simply require too much NFB.

For a better view of this that is both broader and deeper than my explanation above, see Lynn Olson's excellent explanations here, and here

As for tubes' fragility: although they wear out and can break, they are also more likely to survive EMP's, solar flares, lightning strikes, and power-line surges... ;-)

Re:No no no.

[MrKaos]

Actually that's not true, just ask a guitarist (and IAAG - I Am A Guitarist!)

Vacuum tubes create a noisy signal, but in a weird coincidence, they do it in a way that is pleasing to the ear. The clipping and distortion sounds "warm," and there's an added depth in the sound (harmonics) that you don't get via transistors....So, sir, you might argue that you dislike what a noisy tube does to your signal, but you can't say some people won't perceive it as improved, as it's about personal taste.

IAAP and Vacuum amps add a 'third harmonic distortion' to an input signal. Whilst this is desirable for a guitarist, for home listening it introduces distortion that I did not intend to be there when I produced your excellent performance. All that time I spent adjusting the attack and release on the compression to capture those really cool movements of your fingers on the strings are lost because a 'audiophile' decided that they knew better that the people who produced the music in the first place.

Transistor based amplifiers also introduce distortion. Referred to as THD (Total Harmonic Distortion) I like to think of it as 'temporal' distortion. It occurrs when the push and pull sets of the amp cross the waveform (sine) over 0v. It takes about .6v to activaste the transistor and this translates to a 'jag' at 0v of the waveform. It is unlikely that you are ever going to hear it - however that is what semi-conductors are all about, getting more accurate. I think the new class D amps eliminate even this issue, however they use more electricity.

You're right - to some extent it is a matter of personal preference. However home stereo valve amps reduces the "accuracy" of what was intended to be presented to you, the listener and to some extent being an audioophile is an oxymoron. If you like the 3rd harmonic distortion then that is ok, however many audiophiles like to claim this is an 'accurate' representation of a playback, when in fact it is distortion.

Now pick a valve amp for an instrument, then that is different because the valves and electronics are being vibrated by the amplification of yor playing - it sounds cool. You don't get that same effect from a semiconductor guitar amp. My friend and I like to mess around with these amps and do things like changing the transformers to give the amp a more 'ballsy' sound. We took a Musicman 130W valve amp and used Australian sourced transformers as the iron used in them is denser (I'm told) which seems to make the sound more meaty - so it is not just about the valves in the amp.

For my next trick a valve amped Theramin - at least for the pre-amp stage :)

Re:No no no.

[TapeCutter]

more distortion

Metal fans consider that a feature, not a bug.

Re:No no no.

[GerryHattrick]

In my youthful years of building valve-audio, with the faithful Mullard book, the biggest issue was usually mains hum. Rectifying heater current was not a total solution, and the big AC around seemed to jump any gaps however careful the wiring. Anyone remember 'humdingers'? Does the best valve kit nowadays really not hum when no-input is turned to full volume?

Re:No no no.

[Mashiki]

and have shorter lifetimes than solid state electronics.

Going to dispute that one based on my own personal experience. I have a 1925 radio(can't remember who it was made by), beautiful piece of work. Maple case, cherry wood veneer, it is of course all tubes(mix of amplified tubes and non-amped), uses lead solder, has the wiring diagram on the back of the case written in pencil, the person putting it together was smart enough to use wire colours in particular orders and is signed by the person who built it. That in itself is unusual, since a lot of the people who did it just went wild and threw them together half-haphazardly. The wires of course were the state-of-the-art at the time, either cotton-asbestos weave or cotton-rubberized-asbestos weave with a asbestos weaved heat covers when they ran past the tubes. That thing is still going strong nearly 100 years later with the original tubes in it, I use it for a few hours every day just because I enjoy it.

I believe my great grandfather said that he paid $30(around $400 in today's cash) for it at the time.

Re:No no no.

[hughk]

I think the new class D amps eliminate even this issue, however they use more electricity.

It should be the reverse. Class A uses the most power (~20% efficient), Class AB about 60% and D comes in a little under 100% (~90%) or so because the semiconductors are acting as switches dissipating very little heat. The downside is that the high frequency switching can induce all manner of interference which will cause havoc if not properly dealt with.

Re:No no no.

[jellomizer]

A lot of old technology works better than the new stuff. However you will need to be an expert at it to get it that way.
For example the adjustable focus on camera vs the auto focus. Pros use the adjustable focus so they capture the picture just as they want it. For the average person who gets the same camera they will be taking a lot of blurry pictures with an expensive camera. And would be taking better pictures with an auto focus camera.
The same with tubes. A pro can make them sound warm and clear, while the average enthusiast may be better off with a cheaper transistor based device where they can use the money to get a higher line model.

Re:No no no.

[serviscope_minor]

The purpose of a hifi amplifier is to reproduce the small signal as faithfully as possible, and with as little distortion as possible.

Yes but...

I mean I agree and all, but older music often sounds better on old and objectively worse kit than newer music on the same kit. I think the reason for that is you simply couldn't make high power high linearity amplifiers cheaply until relatively recently, and musicians knew that mostly their music would be listened to on the kit of the day, so they wrote and mixed it accordingly.

One could argue that if it was intended for that distorting kit, that's how it should be listened to.

Re:No no no.

[Solandri]

This whole thing reminds me of the filters people have come up with to modify digital photos to simulate different types of film

Re:No no no.

[Applehu Akbar]

The best headphones on the planet use vacuum tubes.

I don't listen to music on my iPhone, but I use a BT headset for driving. Are any of you butthurt Monster Cable audiophiles going to install a Sennheiser Orpheus in your car? Pictures please if you are.

Re:No no no.

[Impy the Impiuos Imp]

You don't need vacuum tubes. That's such a horrible audio myth. They glow in the dark and look nice. Aside from that, they produce more distortion, more noise, use more power, are more fragile, and have shorter lifetimes than solid state electronics. They do not sound better, given $X spent on whatever, presuming some reasonable amount of tech is returned per dollar.

OTOH, if you just want to make vacuum tubes because.... you want to make vacuum tunes... have at it :)

Pretty much. Making your own vacuum tubes, indeed an entire amplifier, is way cool. Doing it because it is "better sounding" is asinine.

So, too, would be making your own Edison wax recorder set.

Re:No no no.

[Type44Q]

Metallica? Tube amps.

Wait, I thought tube amps were good...

Re:No no no.

[k6mfw]

According to a friend that has spent enormous amount of time on sound systems, tubes are better. He said virtually everyone has become so accustomed to transistors sound systems, and now a new generation who only hear music on ipods and phones, their ears cannot distinguish various sounds from instruments. He is also a jazz fan, and is very meticulous of what he listens to (also goes into lot more detail than I can explain here). He also said it takes time to get accustomed to tube sound systems, I believe he mentioned the MacIntosh (nothing to do with the computer company) is regarded as a gold standard, stopped making amplifiers in 1970s but there is someone in SF bay area that can service them. After listening to jazz music on tube systems he claims he can hear certain notes that he cannot hear on transistor systems. I'll probably forward this topic to him though he rarely gets on forums and other places like slashdot.

Re:No no no.

[budgenator]

Tube amps require an output transformer. Tubes use much higher voltages, increasing the risk of painful or deadly shocks.

Why? What goes through the anode, goes through the cathode! The cathode is probably a much closer impedance match to the speaker anyway!

Re:No no no.

[Jawnn]

You don't need vacuum tubes. That's such a horrible audio myth. They glow in the dark and look nice. Aside from that, they produce more distortion, more noise, use more power, are more fragile, and have shorter lifetimes than solid state electronics. They do not sound better, given $X spent on whatever, presuming some reasonable amount of tech is returned per dollar.

OTOH, if you just want to make vacuum tubes because.... you want to make vacuum tunes... have at it :)

You are mostly correct. Vacuum tubes are less efficient, produce more distortion (generally speaking), are less efficient and more fragile, and have shorter life expectancy that solid state components. However, a well designed vacuum tube amplifier will sound better to most listeners. The reason for this is the type of distortion produced. Our ears/brain "hear" a big difference between 2nd and 3rd order harmonic distortion, and it is the former that those glowing glass devices are noted for.

Speaking for myself, and having built several amplifiers based on some of the most respected designs available to the DIY builder, I was absolutely astounded at how much better my first single ended triode (tube) amp sounded than anything I had ever heard. Mind you, I am no clueless audiophile snob. I don't hear a difference between 18 ga lamp cord speaker wires and overpriced, "oxygen-free", "audiophile-grade" speaker wires. I do hear a difference between solid state and an SET, and it is profound. Now, I will qualify that claim by noting that most SET amps are low-powered affairs, that demand rather special (highly efficient) speakers. They are not at their best with loud/complex program material, but when fed a well-recorded acapella vocal group, jazz or classical ensemble, or even some Steely Dan, the result is nothing less than breathtaking. The same can be said for tube-based headphone amps. Not every pair of headphones is a good match for this type of amp.

But then most listeners think that the .mp3 material going through their Beats headpones is "hi-fi", so anyone who can make a buck off that crowd by "sticking tubes in the circuit" is just as guilty of taking money from suckers as is the manufacturer selling a $900 cable that "...increases warmth and air..." In other words, the worth of a given technology is in how it's implemented and not nearly so much in the nature of the components.

Re:No no no.

[Alioth]

Making PCBs isn't all that hard, nor is soldering SMD. I've soldered 0.4mm pitch LQFP chips to a home made PCB. These days I don't bother making the PCBs since there's lots of places doing low quantity PCBs where I can just send the gerbers off to (and get 4 or 6 layer boards, which you need to be obsessed to make at home). I don't even use specialist tools for SMD soldering - normal soldering iron chisel tip, flux, 0.23mm dia solder, solder wick.

Re:No no no.

[HornWumpus]

You really should learn to use an instrument before telling people what it does.

Re:No no no.

[Gibgezr]

The reason real guitarists prefer tubes is because of the distortion.

This is not entirely true. The dynamic known as "pick attack" is also something which solid state amplifier and DSP cannot reproduce with any level of accuracy.

 

Interesting, but Kemper disagrees with you. Their amps even have a "pick attack" knob.

Solid state just doesn't compare.

Solid state does many things well, but it has its own niche.

 

Well these days they do compare. Humans can't distinguish between an amp modeled on (for example) a Kemper modeling amp and the tube amp it modeled. A few years ago it was not the case, but DSP always wins in the end.

Bullshit.

I call bullshit on your bullshit :)
Just watch the following video, where two experienced guitarists do a blind test: https://www.youtube.com/watch?...

Re:No no no.

[Lisandro]

As a former guitarist, i can tell you this: is not so much about the sound, but how tube amps react to ones playing. The old Line 6 stuff, f.ex, already sounded fantastic on recordings back in 1999 but didn't quite "feel" like the real thing.

Having said that: i haven't tried the latest state-of-the-art offerings from Kemper et al, but i hear this has improved a lot since then.

Re:No no no.

[Lisandro]

Yep, switching noise is the main concern with modern Class D amps, but nowadays they just switch at a high enough frequency to make all noise easily filterable from the output. Maxim sells cheap Class D amp ICs intended for audio with a THD 0.05% and a 90% power efficiency.

Re:No no no.

[tlhIngan]

Vacuum tubes create a noisy signal, but in a weird coincidence, they do it in a way that is pleasing to the ear. The clipping and distortion sounds "warm," and there's an added depth in the sound (harmonics) that you don't get via transistors -- unless you create circuits that mimic the behavior of a vacuum tube.

Metallica? Tube amps. John Mayer? Tube Amps. Clapton? Tube amps. BB King? Tube amps. Eric Johnson? Steve Vai? Garth Brooks? All tube amps.

Of course, much of the "tone" we guitarists revere comes from overdriven and abused guitar tubes -- cranking up the volume on the tube so that there's massive distortion and noise -- which again sounds pleasing to some people.

Now, it's one thing to overdrive a tube or change the bias on it to get a particular sound from your guitar, what about building a tube amp to just listen to music?

Well, I suspect this is essentially "remixing" songs. Adding a bit more depth, dirt, or warmth (from the noisy tube) might sound better but that's subjective, and it's all about personal preference.

So, sir, you might argue that you dislike what a noisy tube does to your signal, but you can't say some people won't perceive it as improved, as it's about personal taste.

In other words, you use tubes to process your signal. Any amplification on their part is a just a coincidence.

I get it - its an effects processor. You just keep it in the analog realm, given you can do the same thing digitally afterwards (just without over driving the input).

There are general audio blocks - you have ADCs, DACs and amps, which just have ONE job. Anyone claiming any of those parts are producing a "warmer" or "bright" or "sounds better" is lying because that part is malfunctioning and thus not transparent. (The jobs of DACs and amps is so well defined that we've pretty much achieved perfection).

Then you have a processor, whose job IS to alter the sound, and processors all sound "different" because that's their intent - to alter sound.

And everything that alters sound (EQ, etc) should be kept in processors. A lot of the "tube sound" is caused by the distortion (i.e., imperfect amplification) introduced by tubes, as well as the impedance issues caused (tubes are a high-impedance output, hence the output transformer is required to lower it) which causes EQ because even with a transformer, its still fairly high output impedance compared with the speaker or headphones. (Speakers/headphones have a frequency-dependent impedance, which causes all sorts of EQ to take place - when the impedance is high, those frequencies are muted, etc).

Yes, we solved that, we went to transistors which have a stunningly low output impedance that they can give a flat response to dramatic impedance changes (if you use the 1/8th rule, where output impedance of the amp is 1/8th the nominal impedance of the speaker or headphones, then the variance is around 1dB or so as it goes from nominal down to 1 ohm or lower).

Re: No no no.

[Muad'Dave]

Class A amps run at 50% power at zero input. The amp is biased at 50% on the DC load line.

Re:No no no.

[AnalogDiehard]

Overdriven solid state is like an inflatable date.

Re:No no no.

[NormalVisual]

I think the new class D amps eliminate even this issue, however they use more electricity.

Class D amps are far more power-efficient than A, B, or A/B, and the vast majority of them are also much lighter and more compact, as they don't need a huge output transformer.

Re:No no no.

[ChrisMaple]

Dynamic impedance matching is not really a concern; it's a question of available current. 25 W rms into a 4 ohm speaker requires 3.5 A peak. it's an unusual vacuum tube that will pass even 200 mA, so unless you parallel tubes, a transformer is required to boost the current by 17.5 times, for instance. The transformer of course will simultaneously divide the voltage by 17.5, resulting in a (largely irrelevant) impedance transformation of .306:1.

Transistors are really good at pumping out lots of current, but at high voltages transistors (particularly bipolar transistors) suffer from constraints that make design more difficult: loss of gain-bandwidth product and secondary breakdown. (For very high power audio amplifiers, even 4 ohm speakers have an impedance higher than would make amplifier design easiest.)

Re:No no no.

[ChrisMaple]

Sorry, that should be 306:1, not .306:1.

Re:No no no.

[sysrammer]

"how tube amps react to ones playing". Yes, I agree, it's a noticeable feel. To me, it translates into being easier to play. If something is easier to play, it sounds better. This is yet another version of the assertion "tubes make the music sound better".

Re:No no no.

[ChrisMaple]

You can make a point contact diode in your basement, and that was a common hobbyist trick 60 years ago.

Making transistors with a power gain greater than one is more difficult. If you look into semiconductor history, you might find a way to make germanium point contact or junction transistors with luck and patience. For silicon, you might be able to use photocells as a substrate and spot-weld impurities to make collector and emitter. Just guessing, I've never tried.

Re:No no no.

[rickb928]

Not an amp, but I still have a working Channel Master 6506, red, though most of the electrolytic caps have been replaced.

It was a gift back when it was new.

Re:No no no.

[TechyImmigrant]

I guess my 32 years don't count then.

AB it blindfold and see.
I use a tube amp because it's half the price of a modelling amp ($2k vs. $4K), but it's a compromise on weight and heat.

Re:No no no.

[angel'o'sphere]

You are mixing up three kinds of humans:
a) average humans
b) humans with better hearing than a)
c) humans who are trained to distinguish ... you basically can pick random people from a) and b) train them to her the difference.

Just with tasting of wine.

Re:No no no.

[skribble]

BB King famously used Lab Series Solid State amps (not tube amps). He had used Fender Twins in the past but mostly the Lab's.

Re:No no no.

[TechyImmigrant]

Having said that: i haven't tried the latest state-of-the-art offerings from Kemper et al, but i hear this has improved a lot since then.

It is to this that I was referring. It has indeed improved a lot recently.

Re:No no no.

[TechyImmigrant]

I was only referring to humans who are guitarists who make use of the distortion characteristics of the circuitry between their guitar and the their speaker.

Re:No no no.

[thegarbz]

What you said is quite true. Often once the master is produced from the recording studio it goes through a final level of mixing. This is where music is turned to utter shit by compression and all of that is actually done with a mediocre system as its final intended target.

*sigh*

Re:No no no.

[MrKaos]

Class A uses the most power (~20% efficient), Class AB about 60% and D comes in a little under 100% (~90%) or so because the semiconductors are acting as switches dissipating very little heat. The downside is that the high frequency switching can induce all manner of interference which will cause havoc if not properly dealt with.

You are right. I was confusing a class D amp construction with an amplifier type that has only a single power amp transistor on the output phase - thanks for pointing that out.

Re:No no no.

[Khyber]

Yes, the entirety of the system is original minus the tubes, on a hand-wired thru-hole board. And the system is QUIET. There's no hum. The caps are rock solid.

Re:No no no.

[Khyber]

Here, have a pic of the internals - Nice and clean spaghetti.

Re:No no no.

[budgenator]

Your right, I brain cramped on the current requirement, a 4CX1000A pulls an amp so it would only put out 8 Watts at the cathode, but running through a transformer on the anode, it pumps out 1.6KW

Re:No no no.

[BlueStrat]

Is it really that hard to use JFETs for you?

No.

If they performed, sounded, and felt the same to play through, I'd be using them. Same with power MOSFETs. Heck, I worked for ProCo Sound Inc. building and testing 'Rat' distortion pedals that used JFETs back in the 1980s. I'm well-familiar with their advantages and drawbacks.

I already stated in one of my posts that I'd love to not have to lug around large, heavy, tube amps to get the sound & feel I want. I'm hoping that someday I won't have to. However, as things stand currently, solid-state/DSP/emulation simply isn't there yet.

Strat

Re:No no no.

[Trax3001BBS]

You don't need vacuum tubes. That's such a horrible audio myth. They glow in the dark and look nice. Aside from that, they produce more distortion, more noise, use more power, are more fragile, and have shorter lifetimes than solid state electronics. They do not sound better, given $X spent on whatever, presuming some reasonable amount of tech is returned per dollar.

I'm one of them, analog systems treat music very well, you get the full range (if recorded in analog), Digital systems use sampling, so no matter the sampling rate the unsampled is interpolated.

They do use the power, yet supplied a good sine wave and filtered you have a very fine system, but the question of making a vacuum tube doesn't bode well for the final output quality. Nor safety procedures that need be followed such as grounding http://diyaudioprojects.com/Te... which also plays an important factor in the filtering of the output.

I don't know the OP's skills so many considerations.

Not arguing your points; just a different view.

Re:No no no.

[Trax3001BBS]

Re:No no no. (Score:?)
You don't need vacuum tubes. That's such a horrible audio myth. They glow in the dark and look nice. Aside from that, they produce more distortion, more noise, use more power, are more fragile, and have shorter lifetimes than solid state electronics. They do not sound better, given $X spent on whatever, presuming some reasonable amount of tech is returned per dollar.

I'm one of them, analog systems treat music very well, you get the full range (if recorded in analog), Digital systems use sampling, so no matter the sampling rate the unsampled is interpolated.

They do use the power, yet supplied a good sine wave and filtered you have a very fine system, but the question of making a vacuum tube doesn't bode well for the final output quality. Nor safety procedures that need be followed such as grounding http://diyaudioprojects.com/Te... [diyaudioprojects.com] which also plays an important factor in the filtering of the output.

Cost? it's unimportant for this type of project :)

I don't know the OP's skills so many considerations.

Not arguing your points; just a different view.

--
http://www.iiiiiiii.com/?

Building Scientific Apparatus

[AJWM]

This may well be overkill for your needs, and it's a bit pricey, but the book Building Scientific Apparatus has been on my wish list for a while. It has chapters on working with glass, vacuum technoloy, charged-particle optics, and electronics, among others.

Sigh, too many projects (including a pair of novels to finish) and not enough time.

Re:Building Scientific Apparatus

[Bob the Super Hamste]

charged-particle optics

Now that just sounds way too fun to play with.

Already been done:

[Ellis D. Tripp]

https://www.youtube.com/watch?...

https://www.youtube.com/watch?...

Re:Already been done:

[tsotha]

I love that first link, but I notice he doesn't include a getter, which would reduce the life of his tubes. The second guy uses getters that still have some life from broken tubes..

The tube is the easy part

[Crashmarik]

The vacuum pump that will give you the high vacuum so they won't burn out before you can blink is the problem.
you'll need a diffusion pump as a second stage to a regular pump
something like this
http://www.instructables.com/i...
You will also have to coat the interior of the tube with some sort of getter to keep the vacuum.
and then there are the seals

Re:The tube is the easy part

[Crashmarik]

https://youtu.be/UcRTGVenN9U?t... Need to let those people know, they are using a mercury diffusion pump. I never made an amplifier tube but I sure as hell had to use the diffusion pump for my accelerator (Thank You C.L. Stong and Scientific American for publishing projects that would get people put in prison these days. How I long for my lost homeland)

Apple pie from scratch

[ktakki]

Other than the experience points, I can't see why you'd make your own tubes. Would you make your own transistors?

I've hand-wound guitar pickups and made a ribbon microphone from scratch. Fun stuff, but I could never approach the quality of a stock Fender pickup or Royer ribbon mic.

Sovtek still imports Rusdian tubes, right?

k.

Re:Apple pie from scratch

[thegarbz]

Would you make your own transistors?

Yes. If I could.

Humans pride themselves on learning a skill. Providing this skill is within reach and doesn't require super expensive industrial equipment why wouldn't you attempt to build something yourself?

Some people buy pre-made equipment.
Some people assemble equipment from pre-made modules.
Some people assemble modules using components and manufactured circuit boards.
Some people make their own circuit boards.

The rabbit hole is only limited by your ability to make something that is functionally suitable, and that puts much of the early 20th century within reach.

Re:Apple pie from scratch

[MachineShedFred]

You can find practically any tube you might be looking for on Amazon.com, if you know the part number. Many of the same tubes you can find on the specialty sites that serve audio fetishists who "roll tubes" in their single-ended triode tube amps can be found for half the price on Amazon.

Re:Apple pie from scratch

[Bruce Perens]

Would you make your own transistors?

Yes. If I could.

What is stopping you is that you think you need ultrapurification and microscale fabrication. No. Remember that the first receiving diodes were semiconductors, and while some used germanium it was not unusual to just use a rusty razor blade and the graphite point of a pencil. There are lots of semiconductor materials available to you, and making a cat's whisker is not difficult. It won't be the best transistor in the world, but it will amplify.

Re:Apple pie from scratch

[110010001000]

But why would you learn a skill that is obsolete? That is what I never understood. There are so many skills that can be learned, why choose a useless one? Making vacuum tubes is a useless skill.

Re:Apple pie from scratch

[tsotha]

I think people make tubes because a normal person can with some combination of money and effort - used vacuum pumps aren't that hard to rebuild. You could cheap out and use fixtures, but a reasonable quality glass lathe is something like $14k. It would be a relatively expensive hobby, but still cheaper than cars.

Re:Apple pie from scratch

[budgenator]

If you can't exceed the quality of a Fender PUP, you suck; keep at it, blind chimps can make better, so can you.

Re:Apple pie from scratch

[budgenator]

If you remember how to make an F1 engine for the Saturn5, NASA would like to talk to you.

Re:Apple pie from scratch

[almostadnsguy]

We still have several F1's in several states, we could reproduce the parts with little effort (would have to be made overseas because US has no large scale manufacturing left). I think the real hard part would be putting them together so they work in a complete system.

Re:Apple pie from scratch

[thegarbz]

What is stopping you is that you think you need ultrapurification and microscale fabrication.

What's stopping me is that I need ultrapurification and microscale fabrication. Not that I only think I do. There's a big difference between making something and making something *useful*.

Re:Apple pie from scratch

[thegarbz]

But why would you learn a skill that is obsolete? That is what I never understood. There are so many skills that can be learned, why choose a useless one? Making vacuum tubes is a useless skill.

Because skills are transferable. If you think the ability to blow glass, or to build something that contains a vacuum, or to work with building and manipulating, joinging and assembling fine metal components is an obsolete skill then there's really no helping you.

Side note: I know a vendor of industrial instrumentation, analysers specifically who produces the most wonderful intricate hand-made mechanisms. I could swear this was was machined, but the machining would have been complicated and expensive. I asked him where he found people to do this. Switzerland. Watch makers. The ability to do really fine work with glass and metal is a transferable skill.

Also you need a hobby. Not something you do to further your career, your job, or something like that, but just a hobby. You can easily get enjoyment from doing obsolete stuff.

glass blowing

[ooloorie]

Of course, physics and engineering labs used to "make their own" vacuum tubes. But generally, they had skilled glass blowers on hand who could create vacuum-proof glassware for them. If you really want to try, you might consider starting with chemical glassware intended to be used with vacuums.

Oh my god!

[fustakrakich]

the prices!!. No wonder people want to roll their own...

But the real trick to good sound is the cable, amirite?

Re:Oh my god!

[93 Escort Wagon]

the prices!!. No wonder people want to roll their own...

Those may be "old stock" tubes which aren't made anymore. Since there's no new supply, the prices will be higher - when they're gone, they're gone for good.

Re:If only....

[cb88]

Unfortunately... google doesn't load fast enough on vacuum tube based computers.

Bloatware these days... :/

I love it

[Lewie]

This sounds expensive, time consuming, and ultimately both pointless and rewarding. I love it.

Yeah, no

[fyngyrz]

Okay, we need to discuss classic amplification (IOW, not digital) and tube vs. transistor distortion. Applies to all audio reproduction systems - receivers, preamps, amps, headphone amps.

When run entirely in their linear range, which is to say, in class A amplification, where very expensive and/or high end analog musical system designs sometimes run, analog devices, be they tubes, fets or bipolar transistors, all follow the input signal faithfully, plus or minus total system noise and phase shifts -- no "warmth" or other characteristics are inherent in even a half-decent design, unless you add it yourself with tone controls or the like. *NONE*. For the record, tubes make the most noise, bipolar transistors next, various field effect transistor types the least. Analog integrated circuits tend to use bipolars and/or FETs; look the specific IC up to see, there's no telling otherwise.

So what you want, ideally, is the very minimum of distortion, noise, and as close to perfect signal reproduction as you can get. What goes in equals, as closely as possible, what comes out. But class A is an expensive and power-hungry way to do anything. So most reasonably priced tube and transistor linear amplifiers tend to run in class AB, which uses two devices or sets of devices at the high levek output, where one set amplifies the negative excursions of the signal, the other the positive set. The idea is that the devices are slightly on all the time, and when they begin to amplify their part of the signal, there won't be much distortion from moving into the linear part of their amplification curve from the non-linear, off, part, because the device isn't switching from off to on, it was already on. This works really well, and some very high end tube and transistor equipment works this way. Uses a little extra power, but it's a great compromise.

So what's different in a useful and interesting way between tubes and transistors? Well, when a tube is pushed into its nonlinear range, the gain transfer curve bends over comparatively smoothly so that what would be a sharply clipped (squared off) signal in a device like a bipolar transistor, turns first into a compressed signal, and even later down the curve, begins to evidence harmonic and other distortion that somewhat resembles that produce by hard clipping, but has, because of that still-somewhat-gentle curve, an entirely different set of dominant harmonics as compared to, for instance, a bipolar transistor at or near saturation. So the distortion, when the system is run so hard it distorts, sounds quite different.

That characteristic is why (knowledgeable) musicians who use distortion as a tonal tool often choose tubes; specifically because these musicians *do* run the tubes out of the linear area of the transfer curve, and the result is interesting -- and often pleasing. When the distortion is the result of a transfer curve that abruptly goes from highly linear to highly nonlinear, as is the case with bipolar devices, the result is most unpleasant. Edgy. Sharp. Dissonant. It isn't very often that such a thing is well received in a musical performance.

However, this choice does not *ever* hold true for a musical reproduction system based on tubes that isn't running in a range that will distort the music. You'd have to turn it up so far that one or more elements of the preamp or power amp is pushed past the linear part of its transfer curve, and then all of the music distorts -- and that's not a "warm" sound, that's a "hey, your system sounds awful, turn that thing down before I puke" sound.

So, for example, if I get out my Les Paul or my Strat and plug it into a tube amp and turn that bizatch up, I'm doing so because the amp's distortion is going to very significantly color the reproduction of what I play. I'm going to adjust the amp specifically so I *get* distortion. It'll sound fabulous. I'll get feedback, there will be awesome weirdnesses when I hit harmonics on my strings, pick and fretting artifacts will sound very different,

Re:Yeah, no

[dmbasso]

Awesome post, thanks. What about digital emulations of the analog effects? I implemented some filters for my guitar when I studied signal processing, and it was so much fun, I wish I had more time to kid around with it.

Re:Yeah, no

[fyngyrz]

You're welcome.

You can emulate anything, pretty much. You need a high enough sample rate, enough bits, and a complete understanding of what the effect does, and how it is controlled, if indeed it is.

If you skimp, you'll get... something else other than the original effect.

I write signal processing software pretty much every day. Here's my current obsession.

Re:Yeah, no

[Mr0bvious]

Excellent informative post and explained very well.

I've tried explaining this to people before but you have expressed it so well I'm cutting and pasting that into my collection of "here's one I prepared earlier" answers!

Have you much insight into T-class (tripath) amps. I've heard that T-amps produce the least distortion of all popular amplifier designs, are cheap to make and cheap to drive. Any wisdom here?

https://en.wikipedia.org/wiki/...

Re:Yeah, no

[sjames]

I think some of the confusion may be a holdover from way back when we were transitioning from tubes to transistors. What you said is true for good reproduction amps. But most people have/had mediocre amplifiers. They definitely don't have enough headroom to cover transients and the typical home stereo doesn't even have enough to not distort horribly when turned all the way up. Under those conditions, a mediocre tube amp would sound better than a mediocre transistor amp of that time.

None of that applies to current high end equipment, and there is no consumer grade tube amp unless it's a scam. But then audiophiles tend to believe in special signal conditioned directional cables, magic rocks, and tones through the telephone that somehow condition the room to sound better.

It may also be based on distant memories, but that warmth comes from nostalgia, not tubes.

Re:Yeah, no

[KingOfBLASH]

There are actually apps that let you run all kinds of emulations of classic amps and pedals. AmpKit is one that comes to the top of my head, but there's others.

Just plug an electric into your computer (using a USB interface) and you can push a button and sound like ZZ Top, or any number of presents.

You can also buy pedals that do this. (Just google Fractal Audio). Then plug right into the PA.

Re:Yeah, no

[Anna Merikin]

Wow! Exactly what I've learned in fifty years of audio/broadcast production. I wish I had written it; I certainly wanted to.

I would give the speakers/headphones more emphasis, however. No matter how expensive your rig is, speakers as good will be more. Much more. Including the speakers (especially cheaply-made and poorly designed) in the system evasluation gives an edge to the way bipolar transistors handle transients or square waves. A high power-to-cone mass speaker will follow the sharply cut off curve of a transistor well enough to make a listener's ears bleed, that's true, but a low power-to cone mass cheapie will not; its physics actually complements the transistor's characteristics by not following its sharp peak, but taking its lazy time returning to its accurate excursion limit. In effect, a cheap speaker "smooths' the spikey output of an overdriven bipolar transistor or IC.

But wait, there's more! Psychology is the number one influence. We like what we are used to hearing. We get used to good audio over time, and we become more selective. Or, if we have only heard distortion all our lives, we get to miss bad production if it is absent.

Re: Yeah, no

[Jfetjunky]

You're pretty spot on. Just a few points to highlight. 1. Bipolar devices have the very lowest broadband voltage noise of widely used transistors, with field effect being a bit higher (but with significantly lower current noise). 2. Modern audio devices correct nonlinearities with excessive open loop gain and feedback. This gives them the knee point after which distortion vs frequency begins to rise (because the open loop gain begins to drop vs frequency). It works well but gives the "audiophiles" one more thing to point at, since most tube amps run multiple stages, each with a fixed amount of local gain. 3. The last is psychological, and it's something I had to force my self to come to grips with as someone who literally used to design extremely high performance audio test equipment: If someone thinks something sounds good to them, it sounds good to them. Just like taste or smell. Which is why the whole audiophile mythos exists. 5. 32bit systems are a joke. None of them have low enough noise. For high end systems the first 20 bits might be useful information , if you're lucky. After that the rest of thr bits are noise, and are, from a physics standpoint, hooked up to a gaussian random number generator. Happy listening.

Re:Yeah, no

[FaxeTheCat]

There are a few videos on Youtube where some pretty experienced people try to find what is a real tube amp and what is a Kemper emulated amp. They fail. Not just fail. They FAIL. And admit it.
https://www.youtube.com/watch?...
https://www.youtube.com/watch?...

Re:Yeah, no

[rikkards]

Emulation has come so far in the last 10 years that Geddy Lee of Rush got rid of his amps and went direct into the mixing board through an effects board. So much room was saved on stage they filled the spot with chicken (roasters or washers and dryers if it was laundry day for the tour)

Re: Yeah, no

[piojo]

32bit systems are a joke. None of them have low enough noise. For high end systems the first 20 bits might be useful information , if you're lucky. After that the rest of thr bits are noise, and are, from a physics standpoint, hooked up to a gaussian random number generator.

Are you sure about that? If you use a 20 bit system, you're clipping the noise bits to "0", which won't necessarily be more accurate than letting them remain at their original value. Those bits don't go away--the system still deals with digital values, you've just limited it to fewer possible digital values. This is rounding, and I don't see why rounding away the noise is any more likely to round it in the right direction than wrong.

Re:Yeah, no

[rfengr]

I thought BJT made the least noise; the have lower flicker noise than FET.

Re:Yeah, no

[Falconhell]

A T class a is basicaly a class AB amp, with a class D powersupply.

Re:Yeah, no

[budgenator]

Yeah right, maybe ZZ Top could could like sound ZZ Top playing through an emulator to us, less likely to ZZ Top and You definitely wouldn't sound like ZZ Top, even playing on ZZ Top's rig. 80% of the magic is in the guitarists fingers, not the rig and not the guitar.
  Who really cares anyway, the kids today take a CD of some pop-star, with mediocre quality at best, rip it to a lossey MP3, load it on a smartphone and listen through overpriced headphone and think they are hearing music.

Re:Yeah, no

[budgenator]

I've got 3 phase 408VA running into my power supply and my audio output channels are 4CX1000A's, you insensitive clod

Re:Yeah, no

[judoguy]

And I would give the room more emphasis. I spent a lot of time building out my listening room. I have decent but fairly modest equipment but a kick ass room acoustically. I've been to friends homes with $40,000 worth of two channel stereo equipment in a living room and it was largely wasted. The sad fact is that it's usually way easier to spend money on equipment than to build out a room. I was very fortunate in that I was building a new house so I could design a space. Very few people have that luxury.

Re: Yeah, no

[Anonymous Coward]

And one step further - the room the speakers are in can do horrible, or wonderful things to the audio as perceived at your listening position. (Usually horrible in domestic rooms.)

Spend a few bucks on corner traps and absorber panels (I like rockwool/mineral wool absorbers - effective, easy & cheap to build and look decent) and you'll completely transform your listening experience.

Re: Yeah, no

[Jfetjunky]

You're missing the point. The extra noise adds no useful information unless you apply statistics to improve the overall accuracy on a point by point basis. If the LSBs are dominated by noise, they are literally toggling in a random fashion. The rounding error, which in your example, might be 1 LSB, gets spread over the entire bandwidth of interest.

A SNR of 120dB, which is nearly unheard of except in audio test equipment itself, only requires 19.64bits to represent. It's a mathematical fact. Adding more bits behind that only makes marketing the product more fun.

The only thing that CAN happen, and used to happen, is getting stuck on a bit if the system level noise is well below the noise floor the converter is capable of resolving. This was possible back in the early days of audio, and is responsible for Dynamic Range being tested with a -60dBFS scale signal to force the converter to be excited through a number of bits.

Re:Yeah, no

[phorm]

That's an incredibly reasonable, well-explained, and detailed response. Thank you!

Re:Yeah, no

[KingOfBLASH]

Like it or not certain songs have a "sound" that comes from a combination of pedals and amps. If you want your rendition of said famous song to sound right, you could go out and buy the pedals and amp. Or you could buy a profiler. Your choice.

And I care. Because I play guitar for fun. And you may say that I'm a dreamer. But I'm not the only one

Re: Yeah, no

[piojo]

I'm not misunderstanding the information theory, but I may be misunderstanding the electrical/mechanical context. Does audio equipment use off-the-shelf microchips that are 32-bits, or does every extra bit require more circuitry? I was assuming this stuff is based on computer chips and thus 32 bits is natural--I was just arguing that it's harmless.

Because if your composite data is some infinite-precision data (signal) plus some low-magnitude data, clipping the data does not preferentially remove the noise. It simply changes the low bits to 0, which may or may not agree with the signal. Mostly what got me about your post was the idea that these extra bits are like adding a RNG to the signal. Well, that's true, but so is deleting them.

If making a 32-bit system is harder and more expensive than making a lower-bit system, then I'm fully with you. Either way, charging more for such a system is predatory.

Re: Yeah, no

[networkBoy]

it's not about the CPUs it's about the conversion back to analog:
http://www.analog.com/en/products/digital-to-analog-converters.html
as an example. The higher precision you go (from 8 bit up to 32 bit) the higher the cost.
-nb

Re: Yeah, no

[piojo]

Thanks for clearing that up!

Snake oil.

[jcr]

The difference between tubes and transistors only surfaces when you're overdriving them. Transistors clip, tubes go non-linear. Buy an amp designed for the power you need, and this will never be an issue.

-jcr

Re:Snake oil.

[jcr]

Clipping introduces high-frequency artifacts that most people find obnoxious. When a tube reaches its power limit, the waveform asymptotically approaches the limit.

-jcr

Wire, glass, metal, and a big rocket

[LynnwoodRooster]

Get the requisite materials. Then find a rocket. Launch into space. Open up the pod bay doors. Let the vacuum in. Then assemble. Done!

Re:Wire, glass, metal, and a big rocket

[Bruce Perens]

Let the vacuum in.

Don't you have that backwards :-)

Re:Wire, glass, metal, and a big rocket

[LynnwoodRooster]

Hah! And you probably believe the darkswitch - next to the door - turns ON the light. Everyone knows it turns on the dark vacuum that sucks up the dark from the room!

Warmer?

[grasshoppa]

Does it make it sound warmer? Is it warmer than these wooden standoffs ( 600.00 each ) I got to hold my oxygen-free digital cables off the floor ( a steal at 900 for 6ft )?

Re:Fuggedaboutit

[Osgeld]

They are not made in the USA cause its a obsolete technology with no means to make a profit .... besides the question is about a 1 off project, not making a industry comeback, so quit being a knee jerk dipshit

Why anyone would ever be interested in tubes.

[Bruce Perens]

Various rock musicians prefer tube amplifiers because the conventional tube circuits used since the 1950's, when driven far into distortion, emit even harmonics much more than odd harmonics. This is a perceptually more comfortable sound to the music listener.

Older transistor circuits (we're talking the 1970's) tended to emit odd harmonics.

Obviously you can make a transistor circuit that distorts with even harmonics. However, it is much better to use an amplifier of sufficient power that it is not driven into distortion.

Transistor amplifiers are capable of tremendous power today. I own a 1.3 kilowatt peak envelope power linear RF amplifier using just one or two final amplifier transistors. That is the real power rating, not the fake power rating used on audio amplifiers. It must not distort, indeed all spurious emissions must be 60 dB down, because harmonics would show up as unwanted signals on the radio bands and would immediately be identified as my station. This amplifier weighs just 18 pounds! And that's including the internal power supply.

If you want distortion, use an effects pedal. Don't get it from your amplifier.

Re:Why anyone would ever be interested in tubes.

[KingOfBLASH]

If you want distortion, use an effects pedal. Don't get it from your amplifier.

I'll pit my Dr. Z against your effects pedal anyday

Re:Why anyone would ever be interested in tubes.

[ChrisMaple]

In RF amplifiers, the harmonics are filtered out. The transistors themselves are not particularly linear.

Re:Why anyone would ever be interested in tubes.

[hey!]

Sure but 1.3 KW is not "tremendous" power -- it's amateur range stuff. Broadcast AM stations go up to around 50kw, which is a "normal" for that application.

In the 30s and 40s, WLW in Nashville broadcast at 500KW. Radio Monte Carlo's transmitters currently put out 2x700KW in long wave and an even 1MW in medium wave. Russia's Taldom transmitter pumps out 2.5MW in long wave.

So I'd say anything over 10^8 watts is tremendous.

There are tubes that individually are rated in the MW range, like the 8974 power tetrode, which weighs 80kg and is water cooled. It is rated for 1.2MW (a.k.a. 700 horsepower); in class C it can peak at 2.1MW. That's what I'd call "stupendous" power.

Re:Why anyone would ever be interested in tubes.

[ChrisMaple]

touché. You are correct sir.

Re: Why anyone would ever be interested in tubes.

[Bruce Perens]

My amp is used for SSB, and FreeDV which is a multi carrier modem (several different ones), definitely not a class C amp, it has to be linear.

Re: Why anyone would ever be interested in tubes.

[Bruce Perens]

Sure it is not HAARP. But an honest 1kw in a loudspeaker is lot.

Re:Fuggedaboutit

[thegarbz]

Even if you can do it, complying with the environmental regulations would bankrupt you. That's why vacuum tubes are manufactured in Russia and China, but not the US anymore.

Just what are you smoking? Vacuum tubes aren't made in the US anymore because there's no market for them and Russia and China are the only countries that can support manufacturing for a dead industry. There's nothing inherently bad in making a vacuum tube that would cause environmental regulations to become a limiting factor.

Recycle, Recycle, Recycle.

[Grog6]

Every light bulb or dead tube has multiple glass/Kovar bonded seals.

You can carefully break or melt them out and reuse them; large bulbs are good sources of large connections.

BTW, Neon electrodes are different; they are designed to hold mercury.

Re:Recycle, Recycle, Recycle.

[Bruce Perens]

BTW, Neon electrodes are different; they are designed to hold mercury.

Those are colored phospor cold-cathode tubes. They aren't as pretty as real neon tubes which get their color from an ionized gas, and I wish folks would not call them neon at all.

Re:Recycle, Recycle, Recycle.

[Grog6]

Mercury is a bummer, but if you want bright colors, you want some mercury vapor in there as a charge carrier.

The fun gas is Helium; it's a beautiful orange color.

It's used as a cooling gas; one of the rules I learned was "If you see your equipment glowing bright orange, Don't open the door to the lab!" :)

Re:But the game has changed?

[Bruce Perens]

you simply order a vacuum cartridge and slap that on your 3D printer

I like this idea. This way, your 3D printer can create absolutely nothing where it's useful to do that. :-)

University labs?

[110010001000]

What university lab is constructing vacuum tubes in 2016? That would be idiotic. If you really need a vacuum tube (which no one does in 2017), then go buy one for $10.

Re:University labs?

[Bruce Perens]

What university lab is constructing vacuum tubes in 2016?

Ones that make nuclear accelerators or the emitter in any synchrotron, cyclotron, bevatron, etc. It's a big long vacuum tube.

Sounds like...

[matbury]

...some people spend more time playing with their HiFi than listening to it.

Tubes are still made here in the US....

[Ellis D. Tripp]

But generally only the exotic special purpose and transmitting types. The commodity 12AX7s and 6L6s for guitar amps are all made offshore, due to the low profit margins. The only audio types being made in the US are Western Electric 300B triodes, which are still being made in limited numbers for the high-$$$ audiophool market.

http://www.westernelectric.com...

Other remaining US tube manufacturers include CPI/Eimac:

http://www.cpii.com/division.c...

and MU, Inc. :

http://www.mu-inc.com/webstore...

, who apparently hang on making small runs of tubes to support aging military gear...

I use google

[eledill]

If I wanted to build a vacuum tube, I'd use google and ask it. http://bfy.tw/7lcp

Re:Fuggedaboutit

[ChrisMaple]

He's not going into volume production and he can buy filaments rather than drawing and alloying his own with tungsten and thorium or whatever. This is not EPA territory.

I'm not a tube fan, but electrostatics? Sure!

[mark_reh]

Electrostatic speakers/phones aren't especially hard to make, but sourcing the materials can be difficult. You need ultra thin polyester film for the diaphragms, and some sort of weakly conductive coating (Licron or similar antistatic spray works well). You also need a method of stretching the diaphragm film tight and then gluing it while stretched. I invented a pneumatic stretcher almost 30 years ago when I was into all this stuff. 4693H contact adhesive will stick to the polyester (not much else will)...

Have at it: http://mark.rehorst.com/ESLs/i...

Re:no really, to do it from scratch

[ChrisMaple]

First you have to mine iron ore so that you cane make the shovel to mine copper ore.

Great video

[fgouget]

Claude Paillard has a great video showing how it's done (and photos here). He's built not just his own vacuum tubes but also most of the tools needed to do so. So if you want to build your own molecular pump you'll find data here.

It's possible

[JustAnotherOldGuy]

It's possible to do, but you'll need a fair bit of gear and expect your first few batches to be defective or die soon after powering up.

There are lots of youtube videos that show how it's done, but many of them leave out critical bits of info. As a project in tech school my lab partner and I built a working vacuum tube (we all had to), but we had all the gear we needed and lots of instruction. Even then it was difficult to get t right, lots of failures and lots of "sort-of-working" tubes.

So it can be done, but it's not some wham-bam kind of thing. Ypu're not going to do it in an afternoon, and you sure as shit won't get it right the first time, lol. Ask me how I know.

Expect to invest considerable time and money in getting the gear and experience necessary to produce usable tubes. You have a lot to learn and a million little details to get right, every one of which is either outright tube-killer or produces a tube that initially works but that fails within hours or days. The worst part is if you need more than one tube (like for a stereo amp). Even with carefully-matched components, your finished tube's characteristics will vary A LOT from tube to tube. Again, ask me how I know. :)

You might save yourself a lot of heartache by using old, failed tubes as the base from which to start, unless you want to blow your own glass. Alternatively, get some stock glass tubing and use it to make tubes that will work, but might not be aesthetically pleasing to the eye. Bake the glass (and all the components) thoroughly before assembly to drive out impurities like cleaning residue, fingerprints, etc.

Getting a good, clean vacuum is absolutely critical. It's got to be free of oil mist, particulates, etc etc. This is harder than it sounds. Fashioning a good "getter" and flashing it inside the tube is also tricky. The "getter" helps remove any stuff that outgasses after you've sealed the tube, and it's vital to do it properly.

With all that said, I'll admit, it's pretty damn satisfying to *finally* power one up and have it work. :)

Lightbulb

[backslashdot]

A vacuum tube is a lightbulb with extra electrodes. So he is a video of how to make a light bulb with glass. https://m.youtube.com/watch?v=...

I make tubes!

[Doctorglasseye]

Howdy all, I'm a scientific glassblower (25 years now), and I make my own tubes. I'm at www.incandescentsculpture.com; not much tube info there yet -been a few years in beta mode on them, but some other high-vacuum delights are to be seen. (My handmade incandescent bulbs, my Tesla wireless brush bulbs, the 'fuxie' tube....) Even the production of a simple, low-mu triode is non-trivial; the requisite equipment and knowledge take years to acquire, and a page long essay to even enumerate. OP, I'd be glad to help; perhaps we can compose a FAQ and parts list for kindred spirits.

Recommended book.

[Rufty]

I want to give making my own valves a go, but first I've got to overhaul my vacuum pump, because it doesn't suck. (Well, I need at least 35torr, and it has trouble getting to 120torr.)
I've got this book and like it: Instruments of Amplification.
It's not so much a howto guide as a recounting of "I did this, and this is how it worked". Useful tips on how to cut open bulbs and harvest filaments, how to drill glass, basics of vacuum working and lots else.

Your good advice is useless.

[Zontar_Thing_From_Ve]

You said:

As to making a home-brew vacuum tube, it is doable but not practical. To get predictable performance mechanical tolerances must be exacting and the materials used in commercial tubes are rather exotic and difficult (if not impossible to come close to) for a home-brew vacuum tube maker. What you end up doing is making a tube using 'best guesses' and test/measure the tube's operational parameters and design the circuit around those parameters, rather than the other way around.

There is an amazing amount of exacting engineering, sophisticated manufacturing processes/techniques, and exotic materials science in the old commercial vacuum tubes even by today's standards and is pretty much impractical and beyond the means for the vast majority of private experimenters to reproduce in a home shop.

Strat

I've lived long enough to know that when some dude says "I want to build my own vacuum tubes" that he's not interested in hearing how unrealistic it is.

current vs voltage noise

[Anonymous Coward]

Most devices have different voltage and current noise, so it depends on the source impedance (which transforms the current noise into voltage noise)

A lot depends on the circuit topology as well as the active device. Low noise amplifier design is as much art & craft as engineering - you have to try lots of active devices in different circuits to find the one that is best for your specific application.

Weelllll

[Ol Olsoc]

Making your own vacuum tubes can be fun, rewarding, and a hobby in itself.

But make no mistake, the hobby in itself part is the issue. A person won't dissolve into sound quality heaven goo by spending a weekend making their own hollow state system.

As well, they would get into the audiophile world of what exactly is quality sound. Vacuum tube sound is actually a distortion of the signal, not some hyper fidelity technology - before people get too outraged, I rather like the distortion it gives.

So if a person wants a new hobby - that's a pretty good one. You'll be learning everything that engineers learned about tubes over again, and having a lot of fun doing it. It'll cost a lot, and take some years, but you'll have some awesome bragging rights!

Re:Fuggedaboutit

[budgenator]

A lot of valves require thorium enriched cathodes to assist in thermonic emmisions, and the 5727/2D21W thyratrons have cobalt60 in them; both with EPA/NRC regulations to consider.

Re:A glass lathe?

[mark_reh]

Second lesson: don't believe everything you read posted by anonymous cowards...

Metal vacuum tubes have a glass vacuum tube enclosed by a metal cover. The tube itself is not metal. Glass vacuum tubes are connected to vacuum pumps and sealed off. The getter is there to pick up "stuff" that boils off the filament and out of the other metal parts in the tube, it does not create the vacuum.

Pure artistry

[dskoll]

I don't know how useful it is to make vacuum tubes, but you have to admire this guy's artistry.

This is Making Homebrew Tubes

[ka6wke]

https://www.youtube.com/watch?...

Ahhh, but tubes are second-harmonic

[swschrad]

solid-state is primarily odd-order harmonics. even-order are less dissonant. while audiophools have driven prices through the roof, you can take triode-connected tubes, or Williamson tetrodes, and if you don't work outside the curves, have a sweet amp. there are plenty of "dumpster tubes" at bargain prices that one can work with quite nicely.

Does it have to be a "tube"?

[paulxnuke]

How about a metal enclosure with a bolted flange? It would be massively easier to fabricate and readily repairable or modifiable. No pretty glow, maybe thick plexiglass would work?

If this is a one-off project with nonstandard "tubes", why not put all of them in the same vacuum container? That could look pretty awesome if it was see through.

You could use a big, replaceable getter covered with cheap, relatively safe and easy-to-get sodium instead of dealing with expensive, dangerous cesium into a tiny glass tube (or leave the vacuum pump hooked up, for that matter.) Wiring would be trivial compared to sealing pins into glass, and a six tube box could hold six versions for testing and refining before choosing the best working one, as opposed to building 6 individual tubes to try.

There is this thing called "Google"

[gordguide]

There is this thing called Google where you can search for things, like information, on the internet.
I suggest the OP use it, where they will discover rich information on how to build your own vacuum tubes from scratch.

Now, as to why you would want to, keeping in mind your assertion that it's to build a better vacuum tube driven audio device, I say you are barking up the wrong tree and the commercial efforts, either current production or New Old Stock (NOS) or even good, functioning used tubes (or valves, as those in the UK tend to say) will out-perform whatever you might come up with at home.

Oh, and did I mention the health hazards? Your typical vacuum tube fab was an environmental nightmare. Now you can poison your own yard. Yaaaaaay!

US Environmental Regulations

[AnalogDiehard]

Environmental regulations in the US (and likely the UK) has effectively shut down vacuum tube production in the US by the 1980s. Fabricating the heater/plate/grid/cathode elements is a toxic process. Besides acquiring the equipment, a hobby operation needs some way for disposal of the waste and the local landfill won't accept them. That's why vacuum tubes are made in countries with lax environment regulations (China, Russia, etc).

Electrostatic? Yeah, no thanks.

[kheldan]

I don't know about anyone else, but I'd prefer to not have something being driven by several hundred volts clamped onto either side of my head. One screw-up or failure of the insulation, and you're re-creating a scene from One Flew Over The Cuckoo's Nest in real life.

Glass lathe?

[JustNiz]

>> I need help getting started -- how to put together the vacuum plumbing system; how to make a glass lathe;
Just looking at them it seems clear that the tubes are blown (into a mould), not turned. Can you even turn glass?

Re:Yeah, no (+1)

[almostadnsguy]

+1 for each thing above that I did not know..

I think the highest praise I could have for this..

[HBI]

Is that Julian Hirsch essentially said the same thing over the course of his career. I spent a lot of time reading his stuff in Stereo Review during the 80s and early 90s.

Particularly the bit about the speakers/cartridge overpowering whatever was going on at the amplification end. Except the noise.

Environmental regs had NOTHING to do with it

[Ellis D. Tripp]

So can we skip the right-wing talking points, please? Tube manufacturing was certainly no more toxic than semiconductor fabs are (one of the most toxic industries around), and they aren't going away because of EPA regs.

US tube manufacturing died because the market for tubes went away VERY quickly once solid state devices took over in the late '60s/early '70s.

One example would be RCA, who introduced their first 100% solid state (except for the CRT) color TV sets in 1969, and closed their receiving tube plants (the largest in the US) by 1976.

With 15-20 tubes in a typical color TV set, there was a HUGE replacement market for receiving tubes and many US manufacturers each with several plants to meet the demand. Typically you would need to replace 2-3 tubes a year in a TV you used regularly. Self service tube testers (and replacement tubes) were found in drugstores and hardware stores for folks who wanted to try fixing their own sets.

Once tubes went away in new sets, the market for replacement tubes evaporated within a few years as the older tube sets hit the landfills. The relative handful of tubes still being sold were made in short runs from 1 or 2 US manufacturers who stuck it out until the '80s making a handful of types that still had some demand, but these quietly died by the early '90s, when the US military stopped supporting most of their tube-based gear and flooded the surplus market with warehouses full of unused tubes.

Tubes are still made in the US by a handful of manufacturers, but they are specialized devices used in high powered transmitters, radar, particle accelerators, and such. The ordinary receiving type tubes used in audio gear are largely made in the former Soviet bloc, which kept the remnants of their tube industry alive longer than the West did, preserving much of the manufacturing and raw materials infrastructure needed to serve the modern (much smaller) market for receiving tubes.

Metal tubes only use glass for the seals...

[Ellis D. Tripp]

where the wires from the pins need to pass into the evacuated envelope. The rest of the vacuum-tight enclosure IS the metal can itself. The first metal tubes used tiny individual glass/metal eyelets for each pin, but later ones used a glass "button stem" that held all the lead-in wires in a single piece of glass.

Shortly after the metal tubes were introduced by RCA, some other manufacturers introduced the "MG" types, which were as you describe, a conventional glass tube covered with a metal can. This was done in an attempt to appear "cutting edge" with the then modern technology, but not wanting to invest in the specialized production machinery needed, and to avoid licensing the technology from RCA.

Re:Oscilloscope isn't good enough

[ChrisMaple]

Whether you can see distortion products 30 dB down on an oscilloscope depends upon the nature of the distortion. Crossover distortion (a glitch near 0 volts due to a class AB circuit being too close to class B) is visible. Hard clipping is visible at 30 dB down if you look carefully.

Re:Fuggedaboutit

[skribble]

Not really obsolete for scientific and military applications. Solid state and digitial circuits are quite vulnerable to radiation, where tubes can survive EMP's and magnetism quite well.

Most Heartfelt Thanks!

[mallyn]

Folks:

I am the person who asked the questions and I wish to thank you all very much for your kind replies and help.

This is a hobby for me. I am a retired engineer from Intel in Portland, Oregon and have moved to Bellingham, Washington.

I don't care how long this will take to learn and execute and I don't care if the first 100 tubes/amplifiers will fail. This is to be a journey for learning for me.

I have been known to make stuff that takes a long time to make and do not have corporate/commercial marketability.

As I have no boyfriend; no girlfriend; no husband; no wife; no kids and no pets; and TV sucks and Hollywood sucks and sports to me is riding a bicycle of kayaking and not watching a bunch of millionaires bashing into each other on a green plastic carpet under bright tv lights; I have the time and my entertainment is myself doing these things.

To tell you the truth; once my journey is over and I have a working amplifier; I will most likely give it away or put it onto the shoulder of the road for free and then move onto the next project. It's the process and not the final item that lures me.

Humbly and respectfully yours,

Mark Allyn Bellingham, Washington

Poleaxed by your response

[fyngyrz]

But have you purchased your own telephone pole?

NO? Bloody amateur.

Wondering about the psychophysics...

[bdwoolman]

Firstly let me say that in my 16 years on this site your post is one of the most cogent that I have ever read. Thanks.

But I do want to highlight the fact that sound is an experience shaped not only by the signal but also by the receiver. In this case a person. I think there may be a significant difference in the perception of sound between a trained sound engineer and an average listener. The engineer (that would be you) is trained to treat fidelity as the Grail. Noise is detected by the trained ear as the defect it is and focused upon. And its presence spoils the experience. But most people can and do enjoy music at wide ranges of fidelity. (And given the right conditions so can a sound engineer I would hazard.) And often they do so under noisy conditions and through noisy devices and using lossy CODECS that leverage psychophysical limits for compression. Witness the average person sitting on a city bus with cheap earbuds digging their MP3 music.

To me this explains the vinyl resurgence over CD. And of course the whole vacuum tube thing. I propose that the nervous systems of untrained listeners may actually like a bit of noise because they are used to it and because the universe is filled with it. For 'warm' translate 'noisy' . Perfect fidelity is desirable in the studio as a starting point. And also by musicians, audiophiles and sound engineers. Was it Neal Young who had his MP3s pulled because he could not stand the sound of them? Personally I am fine with a well made higher bitrate MP3.

It would be interesting to know if there have been any focused tests. I have seen it argued that there will be a generation of people who will prefer MP3 sound over Redbook CD sound. (I happen to think vinyl is noisy in a better way than an MP3 which as we know actually has sound info stripped out of the original.) I will close by pointing out that the average visual system also is also made comfortable by noise. Witness the popularity of the filters on Instagram.

Re:Distortion on distortion

[fyngyrz]

When using fx boxes to emulate other hardware, you always want a high-power, distortion-free system that can reproduce exactly what it is fed. This way, when you employ "fuzzbox v.1.9" or "fender jazzman-ish rev 6", or the former feeding into the latter, they sound like those things, instead of those things plus new grunge.

This is typical for studios; the repro system is pristine. Because you always what to hear what's there, not what's there plus something the end listener won't hear, and because as I said earlier, no general *music* repro system should be operating in a regime where it is adding distortion -- because that sucks.

There are plenty of high-power, low-noise solutions that allow emulation to do exactly what it was designed to do. You just have to be savvy enough to pick them instead of that Marshall stack you always drooled over...