Originally Posted by HotIce
Just set your device to the maximum sample-size/bitrate that your device+PC+OS can safely support, and you can drop SW which all it does it selecting them according to source format.
As far as computer audio libraries doing re-sampling, nowadays all such libraries have achieved a pretty high standard.
From authors of a popular player (foobar2000 - which might have interest in claiming their SW sounding better than others WRT re-sampling qualities):
Any decent DAC already has filtering in front of the DAC power source. And for decent I don't mean $1K+.
Even a $2 LC filter, in the proper place within the DAC circuitry, can drop noise to insignificant level.
None of my DACs requires USB "purifiers", and the USB cables leading to them are not exactly short.
A few things which helps reminding:
- USB is digital
- USB packets have CRC
- If noise (or "bad" cables ) fscks up a USB packet, CRC verification fails, and it gets re-transmitted
- If re-transmission rate so high that the downstream device is let starve (according to sample-size/bitrate combo) for data, you have audio skips
- Otherwise, if despite re-transmissions you are within the required device feeding parameters, there are no effects whatsoever in the audio reproduction
- Audio skips are a definitely audible event, no need to guess or invoke spiritual AB tests
- There is no soundstage compression, of female vocals souding congested, or cellos missing their vibe ... the sound just cracks
- If you don't hear audio skips, you need no USB purifiers, beautifiers, magic software managers, or voodoo rituals
The author of Foobar is wrong.
DACs, even little baby ones that rely on ICs for everything, do of course smooth out power supplies. However, when we are discussing noise introduced by USB, the dirty bus noise gets into the power network (rails and ground plane), and even DACs with galvanic isolation on the input (which are uncommon by itself) do not stop all of the noise. The other source of noise is the USB receiver processing USB data which it does at approximately 8 kHz. DACs heavily rely on their clocks to correct the worst jitter introduced by the USB connections, but those crystal oscillators based clock circuits are very sensitive to noise.
USB data is digital, the electric impulse that carries the data is analogue.
USB audio streams do not perform error correction, they are real-time.
Poor quality cables with poor shielding, no EMI rejection, low-quality conductors, fails to conform to USB cable standards, etc, help with introducing jitter.
Breaks in audio occur when the stream is unintelligible and the DAC can't fix it. Jitter introduced by time errors caused by bad cables, naked USB power lines and self-noise, etc, smears the signal in a slight way that nevertheless has a large impact on sound quality. Anyone can buy a Jitterbug for $50 and see the difference for themselves. The Jitterbug simply filters the USB's signal and power lines, and that by itself will have a large impact. The Schiit Wyrd strips the USB bus power and rebuilds the signal from its own power supply and clock (essentially an audio-grade powered USB hub). Higher up the technical competence chain, you have products like the UpTone REGEN that go through further isolation and conditioning of power. Lots of people simply decouple USB from their chain entirely using products that carry audio over Ethernet (which is 100% galvaniaclly isolated from the source). If you have a PCM-only DAC, you'd be better off using SPDIF or AES (which ALSO generate self-noise on the receiver, but they operate at a much slower rate compared to USB so the problem isn't nearly as bad).
If I wasn't so heavy into ultra high-rate DSD, I'd probably just connect to my DAC with a high quality TOSlink cable and call it a day as it is completely immune to power noise and EMI.