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USB Length, jitter and Volume Control Questions

I've been working on a PC audio system for a few months now and I have a few questions that I cannot find the answers to.

I have a new iMac running USB>DacMagic DAC>Onix Sp3>Merlin TSM speakers. I hav had a Valab NOS DAC for a bit and have a Stello DA100 on the way. My questions is how does the volume work in these setups? With the DacMagic I can control the volume through itunes but not through the system menu bar. With the Valab I could control both iTunes and system volume. Is there a difference between the two? Does using the volume control in iTunes or system conpromise the sound? If I'm getting gain from the computer (regardless of system volume or iTuens volume) am I not essentially using the computer as a lowgrade "preamp".

Also, how long can a rung of USB cable be before the signal begins to degrade? Does USB transfer introduce jitter?

Thanks,
mailman199
swampwalker's avatar
swampwalker
5,138 posts
 
That's essentially what it says in my new Music Streamer+- 5 meter max. Interestingly, it also says the shorter the better. Great little (and I do mean little) DAC! Highly recommended.
texas25
40 posts
 
Did you ever try Firewire???
mailman199 OP
34 posts
 
I have not tried FireWire. I have a drobo hookedup to my only FireWire port. Can you daisy chain audio with storage?

I'm also thinking about getting either an airport express to toslink or a 30 ft toslink cable and bypassing USB altogether.

Thoughts?
audioengr
3,282 posts
 
If you want the best results for jitter, I would go with a 1.5m cable for USB. Same with S/PDIF cable for the following reasons:

http://www.positive-feedback.com/Issue14/spdif.htm
mailman199 OP
34 posts
 
Unfortunatly I don't have the ability to use a short cable unless I go wireless (airport express to toslink). My library is 30 feet away.
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