By USB spec I don't think a USB cable can be more then several feet.... |
USB specification says 15 feet |
Yes, USB 2.0 spec is 15 feet. You may get away with longer with slower devices. Also, you just need a cable that meets spec - $20 or so. The only way a USB can "change the sound" is if somehow bits are uniformly changed to alter the sound in a uniform way. Or some bits get flipped and some samples are corrupt and substituted in the player with previous good samples. It's quite easy to determine if your cable is corrupting data. Just connect an external USB drive to your computer and cable and copy files with some sort of data verification (checksums, zip file intergrity test etc) and see if any files get corrupted compared to the source when reading it back. It's very unlikely you'll see and difference between a $20 cable and a $200 "audiophile" USB cable. |
There are active USB extension cables like that one that measures 32ft:
http://www.amazon.com/Meters-Active-Extension-Repeater-Female/dp/B002VG39BI/ref=sr_1_14?s=electronics&ie=UTF8&qid=1288731775&sr=1-14 |
^^^^ That should make it easier for people who don't want to run a cable across the floor from computer "front end" to DAC in rack and people with big rooms. Nice price too! |
Most active USB extensions dont work for audio streaming. I would recommend trying Opticis.
Steve N.
Empirical Audio |
Steve,
Would it work with USB to Toslink Converter? My friend wants to run 30' of cheap IC from the sound card to receiver while his receiver has Toslink input. 30' of USB extension + converter + 3' glass Toslink is perhaps better? |
Steve,
Does the repeater "screw up" the timing of the stream so that implementations that depend on "constant" USB rate for clock recovery don't work? If so, async USB may not be affected. The price is so cheap, I may just get one and try it with my QB-9.
larry |
These repeaters usually interfere with the "back-channel" communications, both adaptive and asyc. They also add a LOT of jitter. Even if you get one to work you will probably need a reclocker to fix the jitter. I have at least one sitting in the reject box.
Steve N.
Empirical Audio |
Thanks, Steve, for the reply. For $15 I decided to try the cable referenced above to satisfy my own curiosity. I connected it between my "front end" netbook and Ayre QB-9. I used my 5M USB 2.0 cable for a total of 15M of USB cable. I couldn't hear any differences. Sounded fine to me. Of course I don't have any equipment to take any type of measurements at the DAC input. And, I was only sending CD data, I don't have any higher rez PCM to try. |
Larry_s,
Thanks for the test. Even if there is a small difference my friend doesn't care and his receiver is more of Mid-Fi. It is still better than running 30' long ICs. |
Let's not forget that Larry_s has an async USB DAC, where the clock is not recovered from the input stream and transport and interface jitter don't exist.
Kijanki, your friend might still be OK, though, and the low price of the USB cable justifies at least a try. What other decent interconnects could one use for the same price? |
Mihaitaa,
That's what I have (Benchmark DAC1) but I use Airport Express across the room instead of long cable, with 3' glass Toslink to DAC. AE has low (250ps) jitter, according to Stereophile measurements, that is further suppressed by Benchmark. My friend tried it a while ago but couldn't make it work. He returned it to Apple store and doesn't want to try again. It was most likely software setup issue. |
Kijanki, I had the Benchmark and liked it, in general, but I found it to be far from jitter-immune. It responded to different transports and digital interconnects, which tells me that it didn't really knock out jitter.
It lowered it though, let's give credit where credit is due.
I bet that if you had a chance to listen to any asynchronous USB DAC you'll see what jitter-free really means and how wonderful computer audio can truly be. Throw in hi-res on top of that and you'll be thanking God for your ears, for without them your smile will go all-around your head ;-) |
