$50 Sound Cards Impress Versus Integrated Audio
crookedvulture writes "Most PCs have audio integrated right on the motherboard. There's much to be gained from upgrading to a discrete sound card, though. This look at a couple of sub-$50 sound cards from Asus explores what can be found at the budget end of the spectrum. In blind listening tests, both cards produced better sound than an integrated solution. They also offered superior signal quality, but neither had an impact on gaming performance. The days of hardware-accelerated game audio seem to be behind us, with developers handling positional audio processing in software."
The switching frequency is well above the limit for audio frequencies, and a good quality PSU will do plenty of filtering. USB to S/PDIF is good for a few reasons: 1) The signal is kept digital, and either differential, balanced or optical for as long as possible. This makes it hard to pick up noise. Digital-to-analog conversion should be done as late as possible because digital signals are very noise-tolerant. 2) Optical connections eliminate grounding issues (less of a problem if you obey #1, anyway). 3) S/PDIF equipment tends to be built to higher quality because it's considered somewhat "high-end" (or, at least, more than a cheap motherboard audio chip). 4) D-A conversion is done far away from the noisy CPU and data buses. It has nothing to do with the SMPS.
You should hear the sound from the vacuum tube guitar amplifier I built. The high tension (300V) is generated by a crappy 50kHz switching boost converter I designed and built myself. The noise on the supply is absolutely awful - 1Vp-p even with only a light load. You can't hear it, though, because it's 50kHz. And that's really low frequency for a SMPS.
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