USB SQ, what can one expect

Willie - a dual cable may help, but it does not eliminate the common-mode noise problem.

Steve N.
Empirical Audio

Cerrot - there are too many folks using USB with great results to make your claims credible. Give it up.

Steve N.
Empirical Audio

USB interface quality varies a lot. Most of them are poorly designed IME. Using power in the cable for the critical clocked part of the interface is a no-no.

However you can improve things a LOT by using a separate high-quality power supply for the USB power. The Power Block is such a USB power supply and the best one available using the Hynes regulation technology. You simply plug the USB cable into it and a short integral USB cable plugs to your DAC. It sits behind your DAC. Email for more details. See:

http://www.audiocircle.com/index.php?topic=128620.0

30-day unconditional money-back guarantee, less shipping.

Another option for you is to use a good USB converter like the Off-Ramp 5 and drive S/PDIF coax to your DAC, abandoning the built-in USB interface completely. This will match or beat your CD transport. More expensive though:

http://www.empiricalaudio.com/products/off-ramp-converter

http://www.empiricalaudio.com/news-and-reviews/off-ramp-converter

Steve N.
Empirical Audio
est. 1996

Erikminer - USB cables will sound different in every system. The reason for this is the USB interfaces vary a lot, the USB ports on the computer vary a lot and each system has different ground-loop noise. All of these play into it.

Steve N.
Empirical Audio

Willie wrote:

"Asynchronous USB interfaces are not sensitive to the quality of the USB cable.

I have personally experienced better USB cables do make a discernible difference i.e. in my system!"

It is true that Async eliminates the problem of jitter from the computer getting into the master clock of the Async interface, however there are other mechanisms that can still cause jitter due to the USB computer interface and the USB cable.

The main mechanism is common-mode noise. The USB interface is differential, so in theory all that matters in the signal is the difference between the two signal wires. However, in practice any noise on both signals (common-mode noise) is not rejected completely by the Async receiver. Because this noise is not completely rejected, it adds to jitter in the Async interface.

There are a couple of ways to eliminate or reduce this noise:

1) filter the USB interface
2) use a galvanically isolated USB interface

I have solutions for both of these:
1 Short Block
http://www.empiricalaudio.com/products/short-block

2 Power Block
http://www.audiocircle.com/index.php?topic=128620.0

Another mechanism that can cause USB cables to differ is the error rate. It is best to get a high-quality USB cable. Same for S/PDIF coax. Use a high-quality cable there too.

Steve N.
Empirical Audio

XMOS provides a tool to record errors on the USB cable. Errors do happen occasionally.

Gordon Rankin believes that they occur often and are the cause of some SQ issues. I'm not so sure...

Steve N.
Empirical Audio

Async USB is not a continuous stream, it is broken up due to handshaking. You have no concept of the science involved. Audio is a real-time process and requires isochronous connections.

Ethernet is explicitly packetized. I have Ethernet as well as USB interfaces and they both perform well. Ethernet can have drop-outs on the network due to its packetization and out-of order arrivals. I will argue that since Ethernet is not a particularly good medium for real-time that it is not well suited to audio, since it is a real-time process.

The main advantage of Ethernet has nothing to do with packetization. The advantage is that the computer OS treats the data no differently than other data. With USB and S/PDIF, the audio stack becomes involved which usually impacts sound quality and creates computer, app and OS dependence.

Steve N.
Empirical Audio

USB can sound as good as vinyl:
http://forum.audiogon.com/cgi-bin/fr.pl?ddgtl&1398132150&openflup&1775&4#1775

http://www.audiocircle.com/index.php?topic=95464
.msg960567#msg960567

Steve N.
Empirical Audio

Cerrot - read the links. Its my customers vinyl, high-end stuff. I don't have vinyl or CD player anymore. My digital sounds better. I have heard your Juli@t in the Bryston. Good sounding, but my stuff leaves it in the dust.

Steve N.
Empirical Audio