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On USB audio: a case against USB 3 , "audiophile" USB cables, etc...

post #1 of 11
Thread Starter 

There are some bizarre questions and claims that surface from time to time in head-fi (sometimes right here in Sound Science), and among those topics are USB cables for audio and the supposed benefits of audiophile-grade cables or the use of USB 3.

 

I thought I might share the thoughts of an audio electronics designer (that some folks might have heard of) on what he thinks about USB audio: J Stoddard. This isn't science fiction, folks.

 

To sum up the main points:

  • USB 3 is completely unnecessary for audio. USB has sufficient bandwidth for multichannel streaming of audibly-transparent, high bitrate audio
  • issues with USB audio often stem from software issues
  • issues with USB audio often stem from 'audiophile' USB cables
  • issues with people using cables outside the USB spec (i.e., too long, or too old with questionable construction relative to the USB spec)
  • hardware configuration issues, especially with USB 3 ports.

 

 

As I and many other members have said before, if you understand and follow the USB specifications for your equipment, everything will be fine. If your cables meet usb specification, but you still don't get proper operation, then one of the connected devices (computer or dac) is malfunctioning and/or broken.

 

The specifications for USB can be found here. There is a plethora of information there!

As always, wikipedia has literature on the topic as well here.

 

Cheers

post #2 of 11

Don't disagree with any of that.   Much the same has been said by Gordon Rankin of Wavelength as well.  Especially that many audiophile USB cables don't meet USB spec.

 

BTW, anyone needing more than 3 meters or 5 meters of USB can use the inexpensive Monoprice USB cable extenders.  Available in lengths up to 87 feet.  They actively buffer the signal so longer runs work.  I have used them and long runs work just as well as a one meter cable.

post #3 of 11
I don't understand why audiophiles focus on things that are so easy and cheap to get right.
post #4 of 11
Quote:
Originally Posted by bigshot View Post

I don't understand why audiophiles focus on things that are so easy and cheap to get right.

 



Most audiophiles have no real understanding of the science behind sound, signal processing nor electronics. They are open to things which are easy to tweak (ie changing cables, power strips etc) and thus it's easy for the saleman to push false ideas into their heads using false analogies which appeals to "common sense" eg if you have a better cable, the sound carried by it will be cleaner/less restricted - because you learned about resistance and how it affects electricity in high school right?
post #5 of 11
Quote:

Originally Posted by ab initio View Post

 

USB 3 is completely unnecessary for audio. USB has sufficient bandwidth for multichannel streaming of audibly-transparent, high bitrate audio

 

USB 3 does have one practical advantage for USB powered audio devices (particularly ones that include an amplifier), although not sound quality related: it allows for higher current draw from the +5 V supply (900 mA vs. 500, further increased in USB 3.1).

post #6 of 11
Thread Starter 
Quote:
Originally Posted by stv014 View Post
 

 

USB 3 does have one practical advantage for USB powered audio devices (particularly ones that include an amplifier), although not sound quality related: it allows for higher current draw from the +5 V supply (900 mA vs. 500, further increased in USB 3.1).

 

This is true; however, I don't think 5V single-ended voltage rails are ideal for power amplifiers. In portable applications where power draw would want to be minimized, what headphones would need more than the 200ma sourced by USB2? and If the application is not portable, why not use wall power where it is much easier and simpler to get cleaner and higher voltage rails?

 

I think the true utility in the increased power sourcing capability of USB 3 is supplying short burst of power to peripherals. Things like hard disks during spin-up, etc..

 

 

But maybe I'm not thinking enough outside the box? What new audio devices would be possible with 5 W worth of single ended 5V power that wasn't possible with 1 W of single ended 5V power? I guess bus-powered portable miniature speakers?

 

My fiancee has these, which are disappointingly quiet:

Perhaps powered speakers is the audio application for USB3. Still, data rate has no affect on these things.

 

Cheers

post #7 of 11

The +5V power supply can be converted to a higher voltage. Even the cheap FiiO E10 (which is USB powered) does this, as it otherwise would not be able to output a maximum level of about 7 Vp-p without clipping. The JDS Labs C5 amplifier is capable of even higher output from a 3.7V Li-ion battery. Boosting the voltage comes at the cost of increased current draw from the +5V rail. Although audiophiles might avoid USB powered devices anyway (assuming that they are low quality), so the advantage could still be only theoretical, after all.


Edited by stv014 - 4/18/14 at 9:14am
post #8 of 11

USB 3.1 will have 20W and 100W modes. That should cover all dac's and headphone amps and most computer speakers. :)

 

Even before this endless wireless charging war ends, USB 3.1 will put an end to separate wall chargers.


Edited by eugenius - 4/18/14 at 9:50am
post #9 of 11
I heard that USB 4 will be able to drive your whole sound system AND a refrigerator full of beer too!
post #10 of 11
Quote:
Originally Posted by bigshot View Post

I heard that USB 4 will be able to drive your whole sound system AND a refrigerator full of beer too!

We already have a usb refrigerator. Well not full of bear... just 1 can of beer tho.

 

http://www.thinkgeek.com/product/96b3/?itm=adwords_labelsElectronics_%26_Gadgets_and_adwords_labelsRegular_Price&rkgid=1143960695&cpg=ogplahe1&source=google_home_electronics&device=c&network=g&matchtype=&gclid=CMfdpp_F6r0CFUqUfgodMwMAOA

 

It actually works quite well.

 

 

People really underestimate the power supply benefit of USB 3.0. We can use more inefficient topology such as class-A or scale up to speaker amplifiers, not to mention we can finally get rid of all of these black-plastic power supplies too.

post #11 of 11

USB 3.0 is 4.5W, not really enough for anything else except portable dac/amps and crappy speakers.

 

If the promised 100W is real at least on desktops (20W on laptops), it can power a pair of 1080p monitors, charge a full size laptop either from the pc or from a monitor with a USB 3.1 hub (yes! no more power brick), run a surround sound system or a pair of good stereo speakers and a dac/amp, light your room and probably many more things I haven't thought about yet.

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