[digitaldave]

Is there any difference in quality between the digital audio coming out of a cheap mother board's USB sockets vs a high quality USB out? I have a relatively cheap motherboard in my PC and also a Mac Book Pro (no idea of the quality), so I'm wondering, given the same DAC, amp and headphones, would the sound be exactly the same? An educated guess says the quality won't make any difference, it's all down to the DAC/amp/phones, but in this game, I wouldn't be surprised it it did mater

.

Hope that makes sense!

Dave.

 

[Currawong]

It might, if the amount of noise going over the USB is different between different computers, or if one computer has a better internal clock (Amarra, from what I can see, uses the input clock in a Mac to send a better timed digital signal to a DAC for example). It would be interesting I think if someone with the right gear could do some measurements to find out.

An interesting experiment one might do with a Mac laptop is, use it as a music server while doing a bunch of other stuff, then do so again just from battery power with everything possible disabled, such as wireless, bluetooth and any other unnecessary software and using a solid-state drive, and see if there is any difference in the sound quality.

 

[Duggeh]

USB is an engineered interface which has a fixed set of specifications. Those devices which match the specification will work fully and without issue. Those devices which do not meet the specifications are not allowed to use the term USB or to display the USB logo. However, things are not always that simple.

This means that audiophile grade USB cables are complete and utter tosh. It doesn't matter if they by dint of overengineering actually surpass the USB spec by any manner, because the interface will not gain anything from it. If however the cable company has just cobbled together something which happens to have a USB connector on each end, and between them lies a hosepipe with MOAR SILVAR, then yes, thats expensive, but does it actually do the job its designed for as well as the cable that came free with your printer?

There are lots of things that don't meet the spec in some way or another, devices that try to draw more than the maximum allowed power from the bus for example.

Your motherboards USB sockets are just the same as the ones on your laptop, nominally. That is to say with portable devices like laptops, or anything which might run off a battery, there are compromises, for example, the USB sockets on laptops might only offer the base level of power output for devices, this means charging will take longer and daisy chaining things to that socket will sooner require the use of a powered hub than it otherwise might.

Another consideration is overall USB bus traffic. If you connect an external hard drive with yoru music on it to a different port on the same USB bus as a USB DAC, then the data is travelling both into and out of the same bus after processing, this can cause dropouts, espeically if the DAC is powered from that bus directly. I ran into this very problem at the UK meet recently because my netbook has all of its USB sockets on the same bus and I didn't use an external power supply for my hard drive or USB transport.

As for mechanical hard drives inserting noise into the USB bus and corrupting the sound output. That's a bunch of complete rubbish. If mechanical hard drives had been causing that sort of signal problem for external connections it'd have been a massively well known issue and quickly resolved. Thats assuming that the issue could ever come up in the first place.
In short. Don't worry about it until the point where a problem actually arises, then ascertain what is causing it. Hope this helps.

 

[digitaldave]

Thanks for the helpful replies. From the sounds of things, the important part of the off board DAC. Now, to work out which one to get... More reading for me!

 

[Phelonious Ponk]

Quote:

Originally Posted by Currawong /img/forum/go_quote.gif An interesting experiment one might do with a Mac laptop is, use it as a music server while doing a bunch of other stuff, then do so again just from battery power with everything possible disabled, such as wireless, bluetooth and any other unnecessary software and using a solid-state drive, and see if there is any difference in the sound quality.

There are plenty of people out there who believe that resource minimization, power supplies, ss drives, etc. impact the sound beyond the DAC, but I've tried exactly the experiment you propose (without the SS DAC) on my MacBook Pro and can't hear the difference. I can cut the resources back to nothing but iTunes, run off of the battery, even shut down the screen...nothing. Sounds the same. I can also switch, very quickly, from coax to optical to USB. Can't hear a difference there either. Maybe I'm just deaf.

P

 

[Mehve]

Quote:

Originally Posted by Phelonious Ponk /img/forum/go_quote.gif There are plenty of people out there who believe that resource minimization, power supplies, ss drives, etc. impact the sound beyond the DAC, but I've tried exactly the experiment you propose (without the SS DAC) on my MacBook Pro and can't hear the difference. I can cut the resources back to nothing but iTunes, run off of the battery, even shut down the screen...nothing. Sounds the same. I can also switch, very quickly, from coax to optical to USB. Can't hear a difference there either. Maybe I'm just deaf. P

No, you're not deaf - it's digital information. The DAC either gets a "1" or a "0", and it takes a pretty serious amount of interference or malfunction to muck things up with a cable that meets USB specs. Unless the argument is that the on-computer processes are somehow creating extra interference that makes it all the way into the DAC's internals, in the analogue portion of the circuitry? Highly, highly doubtful.

 

[ert]

Quote:

Originally Posted by Duggeh /img/forum/go_quote.gif audiophile grade USB cables are complete and utter tosh.

The rubbish coming from audio rags is just making it worse. The latest issue of TAS had Robert Harley talking about how the sound of his USB DAC was better after he upgraded the power cable TO HIS COMPUTER. If computer cables had any impact on performance, the OC gamers would have gotten on this long ago.

 

[gevorg]

Duggeh pretty much nailed it. There won't be any difference, as long as there are no hardware/bus/IRQ conflicts with other USB devices. There *might* be a difference if your USB audio device is using USB power line. Its pretty decent if done right, but with high end systems, USB power should be avoided.

 

[Phelonious Ponk]

Quote:

Originally Posted by Mehve /img/forum/go_quote.gif No, you're not deaf - it's digital information. The DAC either gets a "1" or a "0", and it takes a pretty serious amount of interference or malfunction to muck things up with a cable that meets USB specs. Unless the argument is that the on-computer processes are somehow creating extra interference that makes it all the way into the DAC's internals, in the analogue portion of the circuitry? Highly, highly doubtful.

Well that is the argument; that and the notion that such noise, and process activity, increases jitter. Of course the argument is also that it is all audible if your system is resolving enough, but not measurable. My system is up to the task, so I'm only left to question my ears or the arguments.

P

 

[Phelonious Ponk]

Quote:

Originally Posted by gevorg /img/forum/go_quote.gif Duggeh pretty much nailed it. There won't be any difference, as long as there are no hardware/bus/IRQ conflicts with other USB devices. There *might* be a difference if your USB audio device is using USB power line. Its pretty decent if done right, but with high end systems, USB power should be avoided.

I've tested this one too, running my Trends UD-10 as a digital transport, on USB power and on its optional battery power supply. It sounded exactly the same. It could be that I just don't listen long enough or hard enough. I lose patience with such tests pretty quickly and begin listening to the music instead.

P

 

[MomijiTMO]

Duggeh is my hero.

Anyways, I always get a buzz from reading usb cable reviews. Woohoo, digital is now. . . . digital quality!!!! amazing, same amounts of digital as before!!!!!!!!!

I've also given up on these kinds of debates. No point arguing, people will chose to believe otherwise. No point bringing it up to ruin some kind of friendly chat.

 

[plonter]

i have a question: what about jitter..? does usb jacks (and usb interface in general) produce more jitter than optical or coaxial ?
if the answer is yes, than reducing the jitter amount to minimum (with cables or with certain computer/motherboards configurations, can improve the sound in computers.

 

[Duggeh]

Quote:

Originally Posted by Phelonious Ponk /img/forum/go_quote.gif I've tested this one too, running my Trends UD-10 as a digital transport, on USB power and on its optional battery power supply. It sounded exactly the same. It could be that I just don't listen long enough or hard enough. I lose patience with such tests pretty quickly and begin listening to the music instead. P

I also did comparisons with the battery pack for my Trends unit. I found that there was a huge difference. With the battery pack, you can only use the unit for a few hours, compared to forever off the USB bus. Sonic differences were nil and the battery pack for the Trends is probably the most audio-pointless piece of hardware I've ever tried.

What that Trends unit really needs though is a nice big overbuilt PSU. And not just a wallwart brick either.

 

[shamu144]

"The greatest obstacle to discovery is not ignorance; it is the illusion of knowledge."

But you are right, no point to argue...

 

[Andrew_WOT]

Quote:

Originally Posted by Duggeh /img/forum/go_quote.gif As for mechanical hard drives inserting noise into the USB bus and corrupting the sound output. That's a bunch of complete rubbish. If mechanical hard drives had been causing that sort of signal problem for external connections it'd have been a massively well known issue and quickly resolved. Thats assuming that the issue could ever come up in the first place. In short. Don't worry about it until the point where a problem actually arises, then ascertain what is causing it. Hope this helps.

This noise is the result of ground loop, USB cable in spite of toslink creates electrical connection between computer and external USB audio device, depending on that device PSU implementation that may close the ground loop. Two prong cheater adapters, ground loop isolators or even better Hum-X solve this problem completely.