I would like you opinion on USB noise filter - USB noise reduction dongle.
iFi Audio iDefender+ does offer a dongle at 59€ and AudioQuest JitterBug FMJ at €69€.
But does these products - or similar - bring any improvement on SQ? Or just vast of money?
THX - Have a nice Week 
Torben
They are just a waste of money.
If you have audible noise, like buzzing chirping and the like, when connecting your DAC via USB, I’d rather recommend a true USB isolation device, as sold by Intona.
If there’s no noise, there’s no improvement, it’s as simple as that.
BTW, I’m using said device because of said noise successfully.
That’s one heck of a blanket statement, but I know where you are coming from.
If I was using the (dirty) output from a PC or Mac into a sensitive DAC and wanted peace of mind, I would get this one from Holo Audio. Jeff Zhu at Holo knows his stuff. Cleans up the power and the eye diagram
If you’re hearing noise then you need to diagnose the cause before prescribing the solution. If you’re not hearing noise then you’ve got a clean bill of health!
I would disagree with this. But this takes us down the USB jitter snake oil road. Personally, I believe that there could be non-obvious (i.e. not hearing noise) problems at the DAC, depending on the quality of DAC’s USB input and downstream jitter management. Many take it to unscientific extremes and pay a fortune for it; I’m just suggesting a device which I know has a positive (scientifically measureable) impact on the signal. Is it audible? Only you can say in your system. For peace of mind, $100 seems reasonable vs. lots of the seriously unproven snake oil devices in the $500+ range.
You’re quite correct that spending $100 for peace of mind is a small sum compared to other purchases. It’s definitely each to their own.
At the very least, when you know that PCs and Macs have noisy USB power and terrible eye diagrams which fall below ideal, I think that there is no harm done in correcting that. A “do no harm” (or fix known issues ASAP) approach, but one which might not be necessary depending on the engineering of the downstream USB device (DAC).
I’ve got to admit that I’m not convinced by the catch-all term “noisy USB power”. USB audio is certainly prone to ground loops. but grounding adjustments and/or balanced equipment will overcome this. Other audible problems, related to jitter, can often be down to a badly engineered DAC. But, again, the amount of money we’re talking about for the filter in question is quite small.
EDIT: There’s a measurement review of the Audioquest Jitterbug over on ASR which delves into what is possible when it comes to noise reduction in the audbile range. Take it or leave it, but I post just for info.
I think I read that one. Amir’s statement is uncompromising:
We can easily demonstrate that devices like JitterBug cannot work. USB is a high-speed bus. You cannot filter it without causing the data to be corrupted.
However, the statement is also a blanket one. I think that there’s probably a distinction between devices which “filter” and devices which “reconstruct”, but this is getting beyond my knowledge or recollection.
I do find ASR reviews useful, but your description is definitely accurate!
Not so in my case.
My SMSL M300MkII DAC is connected via balanced connections, but the power converter board in my fan less server generates audible noise even when only the USB data lines are connected.
A true high speed USB isolator from Intona fixed the problem completely.
Using RPi 3B+ or 4 with Ropieee, Diet-Pi or plain RPi-OS did also do away with the noise issue, but I could never get rid of occasional random tics during playback.
That’s why I chose the Intona in-between server and DAC, which fixed that issue also.
If that’s what you want to buy, buy it, but it should be called accordingly, like “USB peace-of-minder”.
As you know, not all PCs are the same, even in the USB department. Most here on the forum are only familiar with pre-assembled big brand PCs. However, when you go into the “choose your own parts and build it” territory, then there are different options that fall outside the “accepted norm”.
USB and 5v power for example. There are motherboards that do have USB implementations which provide clean, isolated and low-noise power while adding the ability to compensate for voltage drop.
Just, like there are fans that are so very quiet even under high load, like some built by Noctua; that really make “fan-less” more of a fashion statement than a noise issue goal.
If a DAC is sensitive to noise from USB, it has poor isolation, which is a design flaw.
Of course it is. If there is a perfect world out there, please point me to it…
I tried one in each ear. Didn’t filter her out in the slightest.
But USB filters can achieve the perfection DACs can’t?
The Chord Hugo 1, which I currently use, is particularly susceptible to USB noises/jitters. When I place a Gustard u12 between a Mac Mini and the Chord Hugo 1, a thick veil has been lifted.
The thicker the veil you can lift with a cheap external filter, the worse the DAC. It’s a shame those DACs cost thousands.