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
herman
2,259 posts
 

Since the digital voltage level can’t change instantaneously (a perfect square wave) it bears some resemblance to an analog signal’s infinite voltage levels.
Not really. That the square wave isn't perfect doesn't make it an analog signal.

yes, we agree, I am only trying to make the point that the digital signal does not strictly meet the definition of 2 and only 2 distinct states since it takes some time to transition. Like I also said, it really makes no difference to the discussion of whether or not USB sucks = a red herring

Analog information is represented by constantly changing voltage levels with an infinite number of possibilities.
That’s a common misnomer. It could only be true if the bandwidth of the analog system were infinite, which is impossible, of course. So just like digital, analog is bandwidth limited. Its resolution is finite.

It is not a misnomer, my statement is  absolutely correct. There are an infinite number of voltage levels between any 2 levels. It has  nothing to do with bandwidth. 
Ag insider logo xs@2x
cleeds
5,954 posts
 
herman
... my statement is absolutely correct. There are an infinite number of voltage levels between any 2 levels. It has nothing to do with bandwidth.
You're arguing that analog systems have infinite resolution, which is simply false. It's a commonly held belief, though.
zerobias's avatar
zerobias
73 posts
 
USB is just fine, thank you very much.  Like everything else, there are many tweaks which can be applied to great benefit.
herman
2,259 posts
 
You're arguing that analog systems have infinite resolution, which is simply false. It's a commonly held belief, though.

I'm not arguing, I'm stating a fact, which has nothing to do with bandwidth or resolution. You are confusing bandwidth which you brought up earlier  and resolution now and whatever else with the simple fact that an analog waveform will, at any point in time, be at any one of an infinite number of possible levels. Anything continuous like an analog waveform has an infinite number of possible points. 

Q: how many point are there on a line? 
A: an infinite number

 Let's say for example your DAC has a minimum output level of zero volts and a maximum of 2 V and the output is a sine wave varying between those 2 levels. If you are correct, tell me what level between and 0 and 2 is it incapable of producing? What voltage levels does it skip on its way from 0 to 2v? 

.0000001 ?
.000001 ?
.00001 ?
.0001 ?
.001 ?
.01 ?
.1 ?
1 ?
1.1 ? 

and so forth

none of these and  none of the other possible infinite number of possible levels between these 




mozartfan
2,143 posts
 
USB for a  DAC??? Never.
USB are for cameras, Cp's
More to discover