2. digital
  3. 159217-149317

USB sucks

USB really isn‘t the right connection between DAC and Server: depending on cables used, you get very different sound quality if the server manages to recognise the DAC at all. Some time ago I replaced my highly tuned Mac Mini (by now-defunct Mach2mini, running Puremusic via USB) with an Innuos Zenith Mk3. For starters I couldn‘t get the DAC (Antelope Zodiac Gold) and server to recognise each other, transmission from the server under USB2.0 wasn‘t possible because the server is Linux based (mind, both alledgedly support the USB2.0 standard) and when I finally got them to talk to each other (by using Artisansilvercables (pure silver) the sound quality was ho-hum. While I understand the conceptual attraction to have the master clock near the converter under asynchronous USB, the connection‘s vagaries (need for exact 90 Ohms impedance, proneness to IFR interference, need to properly shield the 5v power line, short cable runs) makes one wonder, why one wouldn‘t do better to update I2S or S/PDIF or at the higher end use AES/EBU. After more than 20 years of digital playback, the wide variety of outcomes from minor changes seems unacceptable.

Since then and after a lot of playing around I have replaced the silver cables by Uptone USPCB rigid connectors, inserted an Intona Isolator 2.0 and Schiit EITR converting USB to S/PDIF. Connection to the DAC is via Acoustic Revive DSIX powered by a Kingrex LPS.

The amount of back and forth to make all this work is mindboggling, depending on choice of USB cables (with and without separate 5V connection, short, thick and God-knows what else) is hard to believe for something called a standard interface and the differences in sound quality make any review of USB products arbitrary verging on meaningless.

Obviously S/PDIF gives you no native PCM or DSD but, hey, most recordings still are redbook, anyway.
Conversely it is plug and play although quality of the cable still matters but finally it got me the sound quality I was looking for. It may not be the future but nor should USB, given all the shortcomings. Why is the industry promoting a standard that clearly isn‘t fit for purpose?

Finally, I invite the Bits-are-bits naysayers to go on a similar journey, it just might prove to be educational.
antigrunge2

Showing 2 responses by papagiorgio

papagiorgio's avatar
papagiorgio
14 posts
 
USB does carry and introduce a noticeable amount of noise into the DAC, even with high-quality USB cables.  I have found much improved performance by putting an intermediary device in between my music server and DAC.  Today, I have my Mac Mini Roon Server's USB output connected into a SingXer SU-6.  Then the SingXer SU-6 outputs AES/EBU into my Mytek Manhattan II DAC.  This is MUCH improved in noise floor and sound quality, and was very simple to A/B test the Mytek's USB input versus AES.  Also, if I take the WCLK output from the SingXer SU-6, I get a more natural sound from less jitter.

I have also used a Simaudio Moon MiND 2 streamer in the exact same role, and had similarly positive results compared to straight USB.  I upgraded to the SingXer SU-6 so I could support my DSD128 (DoP 1.0) and up to 384K/24bit files via the Myth AES/EBU inputs.  I have heard several other devices that can give the exact same benefits compared to straight USB, so there are a lot of options out there...
papagiorgio's avatar
papagiorgio
14 posts
 
+1 to steakster and Rix.  Since the USB ports of most server devices also provide output power for USB peripherals, they inherently introduce some noise from the music server's power supply into the USB output.  That noise is nowhere near enough to effect the 0's and 1's, but if it is carried into the USB input of the DAC, it can effect the sound quality.  If 1 millivolt of noise were to be introduce into the DAC's analog output, it would create a noise floor at -70dB.

Many higher end USB cables reduce the noise carried from the music server to the DAC's USB port.  Also, using a LPS on the server instead of SMPS generates less power supply noise at the server's USB output.  Converting USB into a format like AES/EBU or S/PDIF that does not carry power also reduces DAC noise.  Even grounding the DAC circuit board (not the same as chassis) will helps to reduce DAC output noise in in some cases.

At the end of the day converting 0's to 1's in most modern audiophile DAC's should yield a good analog output signal.  However, if even a small amount of analog noise is added to that signal output, there is a noticeable change in the noise floor through an audio system capable of 100dB or greater dynamic range.  I know that some people and systems are less sensitive to low levels of analog noise, but I personally prefer my music with as low of a noise floor as possible...
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