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Old Floppy Drive Becomes New Turntable
vinyl1 writes "This must be the ultimate in retro-cool hardware hacking. The floppy drive is obsolete, but the turntable is not, and that got one guy to thinking. He provides a full tutorial on how to turn that worthless old floppy drive into a most desirable piece of audio gear."
The rumble from that stepper motor would be awful. Good turntables go to great lengths to isolate the platter, needle, and arm from extraneous vibration and to smooth out any slight variations in rotational velocity.
Why not simply buy a decent used turntable from eBay? It isn't as if they are all that expensive.
If you RTFA, you'll see that the floppy is being used as a very cheap source of a small, low-vibration, brushless motor and control electronics, with a fast start up and low power requirements so it can be run of batteries, for someone who is making a custom turntable.
~~~~~ BigLig2? You mean there's another one of me?
If you didn't know, a stylus is *not* an integral part of a turntable. It's a component (replaceable or not) of a *cartridge*. They're sold separately, just like tonearms so no ripping up involved.
This project only aimed to build a turntable(plinth, platter, bearing + motor), and not a tonearm or cartridge. They would be much more complex to DIY.
If you RTFA, he is doing it because a customer is paying him money to build a custom turntable.
Someday I'll ge tired of saying "if you RTFA"...
~~~~~ BigLig2? You mean there's another one of me?
As someone who's used his share of cheap belt-drive turntables acquired at garage sales (and then rewired), and who has had some experience at spinning platters this project needs:
Direct drive. There's a reason why DD turntables cost more. Those pulleys wear out, they slip, they stretch on start up and oscillate as they balance out. Why bother with a brushless motor if you're slapping it to a rubber band? Why praise the electronic speed control features of the floppy motor when you're wiring it to a system that by design can't regulate it? Give me torque. When I press that "go" button, I want it spinning perfectly at 33, 45 or maybe 78 RPM, now, not a quarter turn from now. I'm sure there's a way to wire a floppy to do just that, so get back at it!
cf. The Hold Steady, "Everyone's a critic and most people are DJs"
a test tone disc with a track that puts out a steady tone, feed that signal into a computer, run phase lock test or feed a very fine frequency counter. the old way is to superimpose 2 tones into a scope, one from a stable occillator and one from the record, pitch match them,lock the occilloscope and look for wiggles and drift
I just had a quick google, and found this - apparently during the 70's and 80's there were a few such vinyls. Possibly the one you're thinking of was 'New Anatomy' by Inner City Unit?
Another cool example (also mentioned on the site I linked just above) was on a record called XL-1 by Pete Shelley (of The Buzzcocks). If the program encoded in the last track was run while the music played - OH WOW images and lyrics in time with the music!
Those who can make you believe absurdities can make you commit atrocities. - Voltaire
http://mirrordot.org/stories/e40c721288bda9f3e80e1 d99957ec156/index.html
Linkage!
Take a magnet in each hand, like poles toward each other. Move them toward and away from each other. Feel the forces.
How long does it take for the magnets to "recover" from each motion?
Electric motors do not work by interlocked mechanical devices. They work entirely through the EM force field. They self "clutch." The function of a clutch is prevent interlocking mechanical devices from damage. Take an electric model car and set it to running at slow speed. Now grab a tire. The motor will stop turning. You will feel the torque generated by the EM field. Rotate the tire against the force. Now let go of the tire and it will start turning again. If the motor operates the wheel by direct drive there isn't even anything to break.
If the motor is attached to a mechanical drive by a belt slippage of the belt provides additional clutching action, but this is highly undesirable because such clutching takes time; and what you want, as you note, is instantaneous reaction of the platter to the forces in the motor.
Torque is king.
KFG
Here's the history and some review. The story on the site hosting that is also interesting.
At any rate, it looks like the guy who produces that laser turntable does so with proper permission from the owner of the original patent.
...Lots of complaints about how it ought to be a damned vacuum cleaner motor or something. Wow and flutter, etc... Look. The mass of the "table" part and the LP itself are actually going to work in this thing's favor. The drive itself has very fine scale speed adjustments, but it's going to be applied to such a larger mass that the momentum (okay, the Angular Momentum) of the thing will reduce the motor's input to a gentle urge to speed up or slow down. Relatively, of course; the point is it's not going to whip an LP around like it were the moving part of a floppy, but it'll still get it going nice and quickly (YMMV).
The result will be very smooth, precisely controlled speed.
Don't trust anyone under thirty.
Unless they're hearing things above 20kHz, they're not hearing any more information from an analog signal than a digital signal. If we sample at twice the bandwidth of our analog signal we can perfectly reconstruct the original according to the Nyquist Theorem. A CD samples at 44.1 kHz which is enough to cover the standard human auditory range. Now maybe some people can detect frequencies higher than 20kHz, enough that the CD's digital signal cannot accurately reproduce the original frequencies above 20kHz for them, but this is a fault of the 44.1 kHz sampling rate, not digital encoding itself. Digital signals sampled at much higher rates do exist and are used today, just not in your standard CD. So when the CD format changes eventually to allow for higher bit rate recordings, unless these people can detect frequencies above 86 kHz, they won't be detecting anything in an analog signal that they can't in a 192 kHz sampled digital signal. Now, just to cover my ass, yes the frequencies above 20 kHz are still present during the recording process and therefore they will add a very slight amount of distortion to the resulting digital signal. HOWEVER notice that any resulting difference between the digital and analog signal is NOT in the form of missing information but rather in very slightly differing information.
The laws of probability forbid it!
We had to pull the pages from the web site as the amount of traffic to the site killed it! We are working on just making the article available as a pdf document so everyone can download it... If this site can handle the file then we will be more than happy to make it available.. and then maybe we can get out bandwidth back again!!!! The comments raised on this project have been very interesting, and John will be taking some time out to go through the feedback and reply to you about this project he made. Sorry about this technical fup, stuff will be in place in a few hours. Gordon Keenan
#-#-# http://www.it-reality.co.uk #-#-#
Audiophiles are interested in a turntable which:
Has no vibration from the motor transmitted to the platter/tonearm.
Has stable speed (startup speed is unimportant)
Typically you'll see them use fairly low torque belt drive setups (the belt helps with both vibration and speed flutters).
DJs are interested in a turntable which:
Starts fast (thus has high torque)
Has variable speed (pitch)
Doesn't mind being stopped, reversed, etc (there's no "accidental" about it!)
These are typically direct drive units, where the platter actually forms part of the motor itself. For example, in the classic SL1210, the coils are in the base of the unit, and the magnets are mounted right onto the (free spinning) platter. There are no gears, cogs, belts or anything else to wear out. The things are virtually indestructable. It's also worth noting that most of the movement of a record under a DJs hand is facilitated not by the platter but the slipmat - the platter continues turning underneath. This is very beneficial to the startup time, as when you release the record friction grabs it and it's up to full speed right away.
---- Den ene knappen er powerknapp, den andre er Bender voice knapp "Bite My Shiny Metal Ass"
Seeing as most turntables in use these days are used for playing electronic music, I'd suggest either your vinyl or your turntable is screwed. While flutter and wow are problems for sure, they really shouldn't be noticable unless you're listening really hard. On a good setup, they shouldn't be noticable at all.
---- Den ene knappen er powerknapp, den andre er Bender voice knapp "Bite My Shiny Metal Ass"
Hey, there was a good slashdot article about this.../ 21/137259&tid=133&tid=198&tid=141
http://hardware.slashdot.org/article.pl?sid=05/02
Each processor would proceed sequentially as if it had been better for them not to rise against Saul.
Looks like the turntable stopped turning :P
:( How many times do we have to repeat it!)
(use Coral Cache, guys!!!