USB cables and Galvanic Isolation

Look at the measurements on the $199 Schiit Modius. Jitter measures better on USB than coax or toslink. Nothing is perfect but DAC designers are doing a good job with USB. 

USB generates an unpredictable set of outcomes depending on the implementation of USB ports of the server and DAC

Asynchronous USB can affect sound only by the fact that it is connected to something, like computer (injecting noise).  The same applies to any other cable supplying digital data.  S/Pdif coax, connected to computer, can be far worse IMHO.  Ethernet might be slightly better, because of galvanic isolation, but still is not perfect.  Even Toslink, that has no electrical connection can make things worse by amplifying existing internal noise (slow edges).

See the ‘USB sucks’ thread: USB generates an unpredictable set of outcomes depending on the implementation of USB ports of the server and DAC, the quality of the cable and the DAC’s clock as well as the noise environment in the specific setup. As such, galvanic insulation at the DAC is only one requirement for decent sound quality, necessary but not sufficient

@kijanki 
Thanks for the info.  I think it may have been a tube because I haven't heard it since but am keeping my ears open for any further disturbance.  Mostly my computer audio has sound fine.  I've used three different usb cables.  Belkin Gold, Amazon Basics and Monolith.  I can't really make a direct comparison to the three because they are all of different lengths.  They are as follows, 3M, 2M and 1M.

nicktheknife, If you hear it without signal present, then it cannot be caused by the jitter.  Even with the signal present jitter wouldn't show as one frequency, but as added noise (lack of clarity etc).  It is alway possible that electrical noise injected into DAC by any cable becomes audible when multiple noise frequencies mix on any non-linear element (like transistor or diode) producing lower audible frequency (modulation).  This happens on analog side after D/A conversion.  Since it happens in one channel only it is likely a faulty part (like tube), but finding it might be difficult.  It is also remotely possible that right speaker cable (or speaker) is next to something that induces electrical noise into this channel only.

I have owned the DAC it and thought it nice piece of kit for the money. A Brooklyn Bridge would give you a good sounding MQA capable DAC plus streaming.

@nicktheknife  Well it seems my DAC USB module may have just needed a "reset".  I have a Lampizator Atlantic TRP DAC.  In order to use the USB module you have to engage a ring button switch.  Apparently I was able to to make the high pitch noise go away simply by disengaging the ring USB module then re-engaging it.  Presto - problem solved...at least for now.

If you do a search on google there are a lot of reports of high frequency noise produced by USB connections.

three_easy_payments
Good question.  I have wondering the same thing.  I had some noise/distortion come out of my right speaker with my laptop connected.  I had the suspicion that it was just some tube noise ... maybe?

Question for this group.  When we talk about USB noise, what does that typically sound like?  I recently started having an issue with my DAC only when using the USB connection.  It makes a high pitched, almost ultrasonic whine when I begin streaming music from my Lumin to the DAC.  This noise isn't present when I use my AES connection.

Benchmark has very good application notes. I've read most of them their DACs perform very well in reducing USB noise. 

Topping $130 DAC E30 has usb noise in at <-135db, SINAD -112db, USB distribution free range 20 -22 bits 32 tone input at 192 khz. This is attached to dirty USB off a display hub using supplied cable.

Topping D90 comes in with -120.5 SINAD using USB in from computer to XLR out generic cable. Dynamic Range is almost 21bits, 124db channel 1, 123.9db channel 2. 

Yes, electrical noise can enter the DAC but is that really relevant if the DAC has a measure of -120 SINAD from the analog output?

Even if this -120dB SINAD was specified for the USB input signal I'm pretty sure they did not use for this specification a noisy computer with typical USB cable, but rather very quiet custom source (possibly battery operated) and inches long cable.  In addition, according to Benchmark FAQ, jitter effects should be reduced 25dB below noise floor since our ears are extremely sensitive to it.  It is because sidebands, that jitter creates, are not harmonically related to root frequency, hence very audible.
Exact quote:

It can be easily demonstrated that most people have the ability to detect and identify tones which are buried 25 dB or more below white noise (A-Weighted). Therefore, it is important to keep jitter induced side bands nearly 25 dB below the A-Weighted THD+N of the converter, otherwise the jitter may become audible.

and the link:

https://benchmarkmedia.com/blogs/application_notes/12142221-jitter-and-its-effects

Some audiophile cables don't meet the USB 2 certification or haven't  bothered to get them certified. 

One reason I brought up the question of galvanic isolation is that I recently watched a video review of the Chord Qutest by an Australian fella on YouTube.  He claimed to have spoken to the Chord owner or developer (no sure which).  Anyhow, it was emphasized that just a certified usb 2.0 cable be used and NOT an audiophile cable which may be detrimental to the sound.  Something in the Qutest design that doesn't like fancy cables I guess.  I don't have the link but it should be easy to find if anyone's interested. 
That is what got me thinking about GI and cables. 

Amps will have more distortion than DACs unless the DAC is junk and speakers more than amps so if the DAC does a decent job it's not that much of a problem in the system playback. I would say nowadays it's the least of worries. 

Yes, electrical noise can enter the DAC but is that really relevant if the DAC has a measure of -120 SINAD from the analog output? Whatever noise came in has been reduced in the DAC to inaudible levels. It might not be perfect but it’s good enough for human hearing.

USB of newer DACs is asynchronous, meaning incoming data clock and D/A conversion clock are independent.  Sound cannot be affected by the timing of the data, as it is with S/Pdif,  but still can be affected by injected electrical noise (that affect internal DACs clocking).  To limit amount of this electrical noise,  cables with data lines only (no power) are better, when power is not required (DAC has own supply).  Good shielding also plays role to limit ambient electrical noise pick-up.  Galvanic isolation separates two circuits electrically to prevent current flow between them.  It can be done with transformers or optocouplers, but in either case it is not perfect, since there is always very small capacitance between two sides of galvanic isolation, allowing very high frequencies to pass thru.  Nothing is perfect, but galvanic isolation eliminates most of electrical noise.  Another good step would be to reduce noise on the source (computer) side.  That might be difficult since some computers have horrible power supplies.

Why is galvanic isolation so important? I know what the definition is.
What does it improve? Why isn't it used all the time. Galvanic action, is growing barnacles, isn't it? To galvanise, is to Zinc plate iron, right?

So what is galvanic isolation?

Just wondering?

Regards

I've tried Kimber and didn't notice a difference of course I had my wife switch between the expensive and generic cable to eliminate bias. Try the DH Labs you mentioned.

Hopefully Dow Jones will not report this one and get it deleted:

Length does not matter, but preferably short. About 1-1.5 meter no longer, if your equipment proximity allows. 50 cm would work well too.

As for which one, depends on budget. Examples: entry level Wireworld, AQ, Triode Wire Labs, Supra, Sablon

I've made up my mind that I will try a better quality cable.  No harm, no foul.   
Except the question is which one?  
Any max. length as far as usb cables go?

If you listen to (read: read) Dow Jones here, nothing matters, nothing makes a difference, all snake oil, blah ... blah... check out all his posts. You will learn nothing. That's the reason he exists. His hobby.

Do yourself a favor, and try a nice cable. Even if entry level from Wireworld or AQ, or Triode Wire Labs. You may be surprised. We can talk all day here, but nothing is substitute to actually trying.

For those that are wondering I am mostly an analog guy but am interested in building up my digital front with possibly streaming in the future.  I have just been playing cd's and files downloaded on my laptop.
My system consists of a Rogue 99 Magnum Pre, McCormack 0.5 power amp, JVC XL-Z1050 cd player used as transport to the DACitx via rca, Oppo BD-103 for SACD playback, PBN DP loudspeakers and mostly DHlabs BL-1 interconnects. As I said, I'm using a laptop with an Amazon Basics USB cable to the Peachtree DAC itx for playing files. 
 I won't complicate things with the analog front end.  

I see the flat earth contingent has arrived.

Let me see if I can figure this out. You're using a pretty good DAC with galvanic isolation and a basic cable and getting good sound but you read on a forum somewhere that computers generate noise and you need an expensive cable even though as you said you're not disappointed in what you have? Yes, computers can generate noise, are you hearing any noise or measured any? Digital cables either work or they don't, are you getting any sputtering in your music or a high tinny sound? 

So, with galvanic isolation, cable quality (as long as it's certified usb 2.0) is not that critical?

Correct.

Why is cable quality an issue with much more expensive DAC's?

It isn't.

 

Wouldn't most newer, more expensive DAC's use galvanic isolation?

Some do.

Does this mean that the Dac is immune to noise/jitter generated by a computer usb port connected to it?

No. No such thing as immune.

And will a special noise isolating USB cable be required in this instance?

No. No such thing as required.

I've seen a lot of threads touting audiophile usb cables and at present I'm not using one.

"Touting" is close to being right. If touting you mean a story like galvanized this, jitter that. Then yes that is a tout. But if by "touting" you mean people reporting big improvements in sound quality no that is not a tout that is the impression of a listener. Someone actually tried it and heard it was better. That is not a tout. That is an observation. 

The key to your situation is you are now using very ordinary wire. Just possibly maybe one tiny little baby step up from the freebie junk that comes with whatever you bought. That being the case, almost any of the better wires you are looking at will be so much better it will be easy to hear and appreciate.  

Where it gets interesting is once you do upgrade, to find out just how much better a wire can be. Right now starting from zero everything will be amazing. Once you upgrade the improvement with even better wire is still there, only you find more refinement in different areas. Some people like certain things more than others, and so that is why all the different opinions on which is best. But compared to where you are right now there is no doubt, they all are better. 

The Peachtree DAC itx has galvanic isolated USB, you're using it now. You don't need any special cable.