Btw. does anybody use USB chargers and having issues with MIDI? In my case I used a USB chargers to power a MIDI hub, but I got some really serious problems on the DT/DN - whereby I am not remembering well if it was glitchiness or plain noise…
Which ones did you get? I’m struggling to find cheap ones that are usb 2.0 compatible…
I went with the “Full Speed” version of these:
You might need the “High Speed” version though, which is more expensive.
Thanks!
If it USB noise appearing on the audio connection a audio isolator is much cheaper and does exactly the same thing, as myself and @tnussb were trying to explain earlier in the thread.
The audio isolators which I looked at, were more expensive than USB isolators - Full Speed ones at least.
I have used this type, they are very simple, just a pair of isolating transformers inside, obviously they are not suitable for USB noise on USB audio connections which is where I’d use a USB isolator, but for noise on the analog audio jack these are fine and pretty affordable.
1 Like
Do you know of any cheap and small full size jack isolators? Preferable trs for balanced audio (if that even still works)
Behringer HD 400
Thanks! These will not change the quality of the sound?
You’re always taking that risk imo. I decided that it was safer to treat the digital comms side of the equation, rather than to mess around with the audio connection.
1 Like
Degradation of sound quality: Not really. The HD 400 works with a passive transformer, like a DI box. There is a theoretical shift/loss in the frequency curve with low and high frequencies but it’s only oh so slight when measured and in any case not a degradation but a shift, like a passive EQ.
Nothing I was able to hear.
However, for USB noise I would recommend something different:
Get any USB isolator with ADUM4160 chip.
They fix the ground noise at the source. It works with low speed USB devices such as USB MIDI, like keyboard controllers, Keystep, Behringer synths, etc.
Anything that doesn’t transmit audio. For audio interfaces this chip doesn’t work.
Elektron devices actually have USB isolation built in, which is really nice.
The isolator is like 20$ at Amazon/eBay so it‘s worth a try because when it works, the noise is gone without the need to change something in the audio path.
1 Like
HD400 is OK audio-wise, it just loses around 1.5dB on the whole spectrum, and I seem to remember it works/measures best with asymmetrical input cables (symmetrical output cables are OK).
However, the very small (cheap and hugely convenient) audio isolators @darenager linked do suffer from (quite heavy) audio distortion at low frequencies.
They work OK at breaking the ground loop but in some cases, if the audio is bass heavy, you will hear it. At first, I thought I might like it, I didn’t (at all…)
FYI, I confirmed this by measuring them with my AP.
I measured a few different ones with the same size, I think they are all the same internally, small transformers not that good for bass frequencies… but in some cases they are usable.
1 Like
Quite interesting, I had never noticed any distortion, but I will do some tests next time I use one, I mainly used it on the OP1 when charging it via USB, I have also used them on CV on the Squarp Pyramid on occasion. Thanks for the heads up @elektrosamplist
Try with a sustained bass-heavy pad type sound, that’s how I notice it the most.
Audio level plays a role here too, but I have no problem triggering the distortion with a 2V RMS audio line output.
My Lindos measures nearly 30% distortion at +8dBu (and 0.2% at -10dBu), where an HD 400 measures 0.02%
…and I’d recommend using a spectrum analyser plug-in, for visual indication.
So yeah, I’ll just get the usb isolators I guess 
thanks all
Hello, someone have ever tried this kind of stuff ?
1 Like
Interested in this as well
What you saying here Daren? Say I have a powerbank powering two different devices via USB and I get some sort of ground noise connecting audio (3.5mm lead) between the two, I’d be OK with an audio isolator rather than the very expensive USB isolators?