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In Reply to: RE: Synergistic Research USB Cable posted by SeVeReD on February 17, 2008 at 10:43:48
USB is as robust as any other real-time digital interface, such as S/PDIF as far as data integrity. The terminations are not as good, but the data integrity seems fine, even with a 16 footer.
Like all cables used in this mode however, they are subject to skin-effect (for real), dispersion and dielectric absorption due to insulators and losses due to resistance. The more you minimize these, the better the cable will sound. If the USB interface is totally buffered and reclocked (such as my Pace-Car or the Wavelength Asynch interfaces), these affects will not matter so such an expensive cable is not necessary. For conventional USB interfaces that use adaptive mode, it does matter.
Steve N.
> > > If the USB interface is totally buffered and reclocked (such as my Pace-Car or the Wavelength Asynch interfaces), these affects will not matter so such an expensive cable is not necessary < < <
Gee, that sounds familiar! THAT IS EXACTLY WHAT I'VE BEEN ARGUING ABOUT USB DACs (Since they rebuffer and reclock)!!! SO WHY DID EVERYONE CONTRADICT ME???
Actually all USB DACs buffer and re-clock the data. So I guess you're saying that expensive USB cables are a waste of money. If you can find a USB DAC that does not buffer and re-clock, please point it out?
All USB DAC's do NOT rebuffer and reclock the data the same way. Some have very shallow buffers, a few bits, and the "reclocking" is either a PLL or ASRC. Neither of these is immune to jitter.
The only USB DAC's that actually buffer and are immune to incoming jitter are: Spoiler with Pace-Car reclocker inside and Wavelength DAC's that support async USB protocol.
What DAC's are you referring to?
Steve N.
If you dismiss dual stage clock recovery PLLs out of hand as not being immune to jitter then there is no sense in re-hashing my original arguments. We'll just go around in circles again. I know John S insists that PLLs are not efficient as well. I don’t buy it but I'll just drop the entire discussion and invite everyone to purchase a $550 USB cable unless they happen to own your above recommended DACs.
Before leaving I will say this. Isn't it remarkable that Broadcast TV, Cable and Satellite can transmit a 1080i signal with synched 5.1 Dolby surround streamed at > 20mbps without error across tens of miles of nothingness but audiophiles have anxiety attacks with pushing less than 20kbps down 1 meter of cable? And reasonably priced dual stage clock recovery PLLs aren't good enough!
Posted by JimOfOakCreek (A) on February 17, 2008 at 20:13:39 "Isn't it remarkable that Broadcast TV, Cable and Satellite can transmit a 1080i signal with synched 5.1 Dolby surround streamed at > 20mbps without error across tens of miles of nothingness but audiophiles have anxiety attacks with pushing less than 20kbps down 1 meter of cable? And reasonably priced dual stage clock recovery PLLs aren't good enough!"
Yea and my Satellite audio / video broadcasts are 100% perfect 100% of the time-I just can't figure out why my english broadcasts look like Japanese lip synching. Digital perfect sound (and sight) forever? I sure am grad I didn't get rid of my old LP's.
I don't have that problem with TW Cable nor with over the air broadcasts (I find PBS always perfect). I don't have Satellite so I can't judge.
Steve,
I have a Wavelength Async Crimson and a Wavelength Async Brick ver 2 here. The Synergistic cable makes a big difference with these DACS.
Are you sure the brick is Async? I though that Gordon had only released async for Crimson and was planning Cosecant.
If this is true, then I dont have an explanation. In theory, if the implementation is done correctly, async should disregard ANY jitter from the USB interface.
Does Gordon use the power from the USB cable for anything in the DAC?
Steve N.
Yeah, I agree, if the interface is async, there should be no effect, unless the cable is one of those crummy stock cables.
Steve,
The version 2 Brick I have now is Async. I don't think Gordon uses the power from the USB cable for the DAC. Gordon will hopefully chime in on this tomorrow. I really have limited knowledge on the engineering end of all of this.
At least he was awhile back.
.
mercman (Steve),
audioengr states that USB cable quality should not make a difference with the new ASYNC format. Is your Crimson not udated with the ASYNC interface and if so, I wonder why there would be a noticable difference with the new cable.
Also, is a USB cable and I2S cable not the same thing - I think I'm confused.
USb is a cable from the computer to the audio converter, usually USB to S/PDIF or USB to I2S. I2S is the interface to the D/A chip. If you do USB to I2S, you avoid the conversions to S/PDIF and the clock recovery from S/PDIF.
The USB cable has one signal pair and a power pair. The S/PDIF cable has a single signal pair. The I2S cable has 3 or 4 signal pairs, usually one data pair SDATA, one L/RCLK or "SYNC" pair, one MCLK or master clock pair and one BCLK, or bit clock pair.
Rio Tubes laid it out for me in the link below about usb & I2S. I'm betting that even with ASYNC or pace car or whatever... the higher your dac/system is in resolution the more one hears digital effects in cables.
Steve
Thanks for addressing USB robustness... I remember I use to drive myself crazy listening to the differences in dig coax cables too (back in the ol cd transport to DAC days). I chose an Orchid cable back then that I liked. So, ya, nothing magical or more robust about coax either I guess.
Hope to talk with you within the year about possible configurations/needs using your stuff.
Acer Aspire 9500 laptop Pentium 1.73GHz w/ 2 gigs ram, Vista Premium 32 bit, WAV/CUE files on Hard Drives via firewire, XXHighEnd ver. 0.9T-5 Player Q1 18, player priority nothing,thread priority real-time; Stello 100 USB-DAC nos
Certainly both S/PDIF and USB cables can cause timing effects or jitter. This is why better cables in both cases can improve the sound with most interfaces.
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