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+---- Thread: DIGITAL NOISE (/Thread-DIGITAL-NOISE)
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DIGITAL NOISE - Chello - 04-23-2026
DIGITAL NOISE
For a long time I thought I was the only one bothered by this.
I first noticed the problem when USB was launched - everything based on this had an intolerable noise that was especially annoying around 15kHz to 25kHz.
Many claim that bad USB cables are the cause, but I have replaced all of them with expensive versions - without ANY change.
However, there are several factors that come into play, such as the individual's ability to perceive such high frequencies - most people over 37 have severely reduced hearing above 10kHz, while I am "blessed" (or cursed..?) with being able to hear frequencies up to 25kHz or higher.
Secondly, very few people have speakers that are capable of reproducing such high frequencies, while I have had them for many years.
A good DAC/AAC that handles 24 bit (or more) is also necessary.
Thirdly, there are not many recordings that have such high frequencies, and all Mp3 is excluded, while Wave and FLAC can have them, and DSD/SACD is the best, with 24 bit - or higher.
It is important to know that Wave and FLAC are often only 16 bit (CD "quality"), which gives a greatly reduced resolution compared to 24 bit.
A lot of recordings that are available as SACD/Wave/FLAC are actually 16 bit Wave that has been "converted" to 24 bit SACD/Wave/FLAC, which means that they are only 16 bit - it is practically impossible to increase the bitrate by conversion - well-trained ears hear this immediately.
Back to the point:
Digital noise.
I have experienced digital noise for years, even with quality products such as the AUNE S6 DAC and MOTU M4 AAC, which both support 32 bit.
Both of these have the best chips on the market installed.
Another source of problem is the amplifiers used; are these analog or digital ?
Analog amplifiers such as tube are the worst of all, as they act as an antenna to digital noise - mobile phones and the like emit an extreme amount of digital noise.
Ordinary analog ones that are particularly well shielded can work quite well, while digital ones that are very well shielded are the only ones that work well enough.
Digital amplifiers with poor shielding are a nightmare.
So how to solve the problem ?
The most effective thing is to place the PC as far away from the program sources as possible, while I pretty much have to have the PC placed close, which maximizes the problem.
So other solutions have to be tried, and the only effective one is USB Isolation.
Some time ago I acquired one of these, and this works quite well with the AUNE DAC, but has no effect on the MOTU AAC, probably because this gets power via USB C.
I have recently acquired a new sound card, which is also USB C based, and have also ordered special USB Isolators for both USB B and C, which can be connected to each device.
Hopefully these will reduce the noise to a tolerable level.
I have planned a test of this new sound card, but will have to wait until I receive the USB Isolators.
I will get back to the subject as soon as possible.
RE: DIGITAL NOISE - mb_pa5x - 04-27-2026
Chello, thank you for your post about this annoying USB noise. Very informative!
I have the same issue with my Pa5X and ModX connected to a mixer and the MODX by USB. When I disconnect the MODX USB connector the noise is gone. Can the unbalanced audio outputs of the MODX in combination with USB also be a source of noise?
I wasn't aware of the existence of USB-isolators. I'm really curious if they work well. Don't know if there are any disadvantages using USB-isolators.
Worth investigating!
RE: DIGITAL NOISE - Chello - 04-27-2026
(04-27-2026, 10:24 PM)mb_pa5x Wrote: Chello, thank you for your post about this annoying USB noise. Very informative!
I have the same issue with my Pa5X and ModX connected to a mixer and the MODX by USB. When I disconnect the MODX USB connector the noise is gone. Can the unbalanced audio outputs of the MODX in combination with USB also be a source of noise?
I wasn't aware of the existence of USB-isolators. I'm really curious if they work well. Don't know if there are any disadvantages using USB-isolators.
Worth investigating!
✪mb_pa5x
Many thanks for showing your interest in this topic.
Very few people say anything about it, and perhaps this is because they don't hear it, which could be due to the equipment used or impaired hearing; many people don't hear much above 10kHz, while the problem becomes pronounced at much higher frequencies.
The better equipment and hearing you have, the worse the experience.
I noticed the same thing with MODX as you.
Unbalanced audio outputs should not have an impact, but I haven't tested this.
Something that always helps, however, is to place the PC as far away from the equipment as possible.
The USB isolator I have works well with the DAC - it removes almost all digital noise, but it had no effect on the sound card, which was USB C powered.
I have ordered 5 USB B and 1 USB C isolators which I expect to receive tomorrow morning, and will then test their effectiveness.
There are no known disadvantages to using USB isolators; on the contrary.
The problem with digital noise is because a PC is usually completely unshielded with a plastic case.
Previously I used a 20 kg heavy steel case, and this gave almost no digital noise.
My current one is made of plastic, and is placed close to the amplifiers, which maximizes the problem.
My new amplifier is very well shielded, so that I now have very low noise even at full volume, but I can still hear it well if it is otherwise completely quiet in the room.
I am very excited to see how good the new isolators are, because they are quite cheap and can be plugged into every component in the system.
RE: DIGITAL NOISE - mb_pa5x - 04-28-2026
Thanks Chello! I'll try moving my PC, it's now next to the mixer and studio monitors.
Which brand USB-isolators did you order? On the internet I see different brands, cheap and expensive ones. Maybe the cheap isolators work perfectly in my setting.
I'm excited to see what your results are.
RE: DIGITAL NOISE - Chello - 04-28-2026
(04-28-2026, 10:15 AM)mb_pa5x Wrote: Thanks Chello! I'll try moving my PC, it's now next to the mixer and studio monitors.
Which brand USB-isolators did you order? On the internet I see different brands, cheap and expensive ones. Maybe the cheap isolators work perfectly in my setting.
I'm excited to see what your results are.
✪mb_pa5x
Moving the PC is usually enough - test if there is any audible change.
I ordered these:
I have now tested, and was shocked by the result:
I use an AUNE S6 DAC, which provides 32 bit/384 kB resolution with Windows, and 64 bit/Float with Mac.
But the isolator only allowed 16 bit/96 kB resolution; so what's the point then..?
And the noise was unchanged.
I also had a real nightmare finding a new driver for the DAC, because the Windows driver crashed.
So tested USB Isolator is completely useless.
On the other hand, I have long used TOPPING HS02 USB ISOLATOR for the Aune DAC, which costs about 100€.
This works well and can be recommended, but remember to turn it the right way, otherwise it will bang !
Follow the manual precisely, and there is no risk.
The Topping isolator was unable to drive my previous MOTU M4 sound card, probably because this is USC C based and requires too much power.
RE: DIGITAL NOISE - Chello - 04-28-2026
Final test
I finally tested with the TOPPING HS02 USB ISOLATOR - the noise was a little lower than without.
But I noticed a slight "click" every now and then, which has not been there before.
This is difficult to understand, because this click was not there with the MBL preamplifier..?
But the noise was significant higher without the isolator.
So I choose to run WITHOUT the isolator, because the noise level with the new preamplifier is unproblematically low.
RE: DIGITAL NOISE - mb_pa5x - 04-28-2026
What a pity to read that the isolator did not remove the noise completely. An isolator seems not to be the ultimate solution. Thanks for testing Chello!
RE: DIGITAL NOISE - Chello - 04-29-2026
(04-28-2026, 10:33 PM)mb_pa5x Wrote: What a pity to read that the isolator did not remove the noise completely. An isolator seems not to be the ultimate solution. Thanks for testing Chello!
✪mb_pa5x
I was prepared for a half-hearted result using a USB isolator, even though many claim that the noise has disappeared completely - the one I tested has also received positive reviews from users.
The ultimate isolator on the market is one from Topping - U90 USB bridge, which costs about 500-600 dollars..!
This is supposed to remove ALL digital noise - guaranteed, but I don't believe in fairy tales, because if you have poorly shielded components in the chain, these will affect it anyway, and you can end up with Topping having to work so hard that it itself produces noise.
Relying 100% on an isolator removing all noise is like trusting that a crossover in a speaker can fix all the problems that the units have.
One of the most notorious examples is the Infinity Kappa 9 with its complex units and complex crossover, which has extreme dropouts in the impedance curve resulting in resistances down to 0.5 Ohm..!
These have probably killed more amplifiers than any other speakers, even though the sound can be very good.
The design of the Kappa 9 is backwards, because the right thing to do is to minimize the number of components in the crossover, and rather choose units that are the best possible.
I have restored the Kappa 9, and know very well how they are constructed.
I have the following recipe for avoiding digital noise:
1: Make sure your equipment is connected to a separate grounded circuit in the house (I don't have this yet).
2: Only use (thick) signal cables that have good shielding; XLR if possible.
3: Never use standard USB cables, but a type that is better shielded.
4: Choose a high quality DAC - I have had cheaper versions of AUNE and others, which have given significant noise - the AUNE S6 is one of the best, as good as the best that cost about 3000 dollars.
5: Choose an amplifier with good shielding - avoid tube amplifiers (which act like an antenna to digital noise). My FM Acoustics is excellently shielded, as is my XTZ, which also has digital connections - these two are the best I've had in terms of noise.
6: Choose a PC with an Intel processor and not one with an AMD processor, and use a solid metal case that provides effective shielding, which a plastic one does not. My main PC uses (unfortunately) an AMD processor, and has a plastic case. 3000 dollars straight out the window...
I have an old Intel that is almost completely noise-free, but this one has too few connections for my use.
7: Place the PC as far away from other equipment as possible - this will often eliminate the problem of digital noise.
The best option for eliminating digital noise is therefore to follow these 7 recommendations.
A USB isolator cannot magically eliminate noise, if the sources are numerous and serious.
Never spend a fortune on expensive cables, because they will not solve the problem.
If you follow recommendations 1, 6 and 7 in particular, all noise will probably stop.
RE: DIGITAL NOISE - mb_pa5x - 04-29-2026
Chello, thank you for your extensive and helpful answer! I learned a lot since I discovered this keyboard forum.
RE: DIGITAL NOISE - Chello - 04-29-2026
WEAKNESS DISCOVERED WITH TOPPING HS02 USB ISOLATOR
After testing this isolator with my new amplifier connected, I have discovered a serious weakness with the isolator:
A weak to loud click is heard all the time, but becomes especially annoying when the resolution is increased on the DAC - a 24 bit audio file is for example much worse than a 16 bit, and 32 bit is intolerable.
There is no point in using this, when high quality formats such as SACD, DSF and DSD get these clicking sounds, which I find extremely intolerable.
There is also a strong distortion of the bass reproduction, while the perspective is very shifted and incorrectly reproduced.
I have seen that the most expensive of Topping's isolators "guarantee" to support the highest resolutions, but I have a hard time believing that this actually works properly no matter what you pay.
USB Isolators ? NO THANKS !!!