USB-powered synths and ground loop hell, help!

[sinedie]

I'm trying to assemble a full portable setup composed exclusively of USB-powered gear, but I'm having a hell of a ground loop issue (not interferences).

All my gear is powered from a single USB power supply:
- Digitone & Digitakt (with ripcord USB adapters)
- Dreadbox Typhon
- OP-Z
- Korg NTS-1
- Korg nanokey studio
- 1010Music Bluebox
- Raspberry Pi (acting as Midi Host/through)

As soon as I plug anything into the Raspberry Pi for midi, the ground loop hum comes (heavily!).

The Digi's, Typhon, Bluebox and Raspberry Pi are directly connected to the power supply.
Then, the OP-Z, NTS-1 and Nanokey are connected to the Pi for both power and midi (no other possible choice here).
If I run the OPZ or NTS-1 from battery, there's no hum (but no midi). Every time I connect a device to the Pi for midi, the hum appears for that device. If I connect the Digi's to Pi for USB midi, the hum is also there.

Basically, as soon as I connect anything to the Raspberry Pi the ground loop comes in... I thought that powering everything from the same power source would avoid these kind of issues, but I was completely wrong

Here's a video with a minimal reproduction of the issue with the Bluebox, Pi and NTS-1: https://photos.app.goo.gl/ciRY2NbFNmug9brW7

What do you think would be the best approach to get rid of the ground loop? It seems I need a USB hub that would isolate the ground of each device plugged in, but I'm not sure where to find such a hub.


PS: I also posted this on reddit to try to find a solution

[Georges]

Try plugging the bluebox directly into the wall plug or the outlet and not to have it connected to the usb hub.

[sinedie]

The bluebox is not connected to the hub, but to the power supply directly.

If I power the bluebox from battery, it solves the problem partially: The digi's are fine now, but the OP-Z and NTS-1 generate noise that cancel each other when plugged at the same time. If I mute the OP-Z or NTS-1 I hear the noise, but if I have them both on at the same time the noise is cancelled (but I still see the signal coming in in the mixer). If I shut down either the OP-Z or NTS-1, no more noise.

The problem is that I don't want to run it from battery :/

[peanutbuttersolution]

I anticipated having similar problems, but haven't had any issue so far. I've had good luck by NOT sharing a USB power supply. I sprung for a big surge protector that can handle a whole bunch of wall warts so everything is into the same wall outlet ground but floats on their own. I have both an NTS-1 and a Typhon in the mix. The Typhon is very susceptible to ground loop noise. When I use it connected to a USB audio interface I have to use a battery to prevent noise. For the NTS-1 and typhon, I use an Anker brand USB wart, again, one per wart, and so far they're playing nice with the bluebox.

https://www.monoprice.com/product?p_id=15874&gclid=CjwKCAiA65iBBhB-EiwAW253W27wA6TVPBJXx-WDMZ2pRiqw4xPZBQ-CSz2N41V1OipB5wR82W_7gxoCsqkQAvD_BwE

[sinedie]

That's a problem for me, as I'm trying to build a portable setup, hence why I'm powering everything from the same USB power supply :/ Maybe I'll have to rethink the setup a bit

Indeed running the Bluebox from a separate power supply I have the same result as running it from battery: no more ground loop (still a win!), but it didn't solve the issue completely as there's now static noise when NTS-1 and OPZ are on at the same time (see my previous post).

Worse, as for the OP-Z and NTS-1 I don't have the option to power them separately as I use USB-MIDI, so only choice is to connect them to the Pi. I've ordered an iDefender (https://ifi-audio.com/products/idefender-plus/) to add put between the Pi and the OPZ-NTS-1 and see if it solves the issue.

My Typhon hasn't arrived yet, but since it has the option to use standard MIDI I'll use that, as thankfully MIDI signals are isolated.

[kitejan]

This is exactly the problem I'm having.

I was hoping to run everything from either battery, USB power (Bluebox, NTS-1, KaossPad), or a GuitarPedal PSU (Circuit, Monostation, Volca Modular, Migrogranny) - so the ideal would have been 2 power plugs for everything. However I found that the noise was extreme , I've found that the NTS-1 and KaossPad cant share a USB power adapter either, plus the Volca is suddenly noisy where it wasnt previously in my Behringer mixer.

So I'm looking around to see if my "vision" (or "cunning plan") is possible, or not. I just hadn't realised there were so many issues with USB powered things - or indeed passing data over USB - between synth devices. And I haven't started considering how to integrate the hardware stuff with all the ipad based apps (I had wondered if connecting the ipad to a powered USB hub which passed power and MIDI where needed to the devices would work) - that's the next step :-)

I shall carry on researching possible solutions.

Jan

[0101-Usr]

I use portable version of my setup powered by one 5 USB outputs powerbank or 6 USB outputs power supply. There are a lot of ground loop sounds, but I use cheap audio filters for all BB outputs and it's gone almost at all. I didn't compare spectrum of sound, warm etc, but for live jams it just sounds good for me.

https://www.aliexpress.com/item/1005001604545947.html

Take no less than 6 for BB It works with L/R splitter too (it's stereo filter).

[kitejan]

@0101-Usr - thanks for that. I had seen those mentioned as an option. I've ordered one to try out to see if it solves the problem - if it does I will get some more.

[0101-Usr]

I did it too... and then ordered few more

[sinedie]

Be careful with these cheap ground loop filters, as they introduce HUGE distorsion in the bass spectrum. No easily hearable in headphones, bug on big PAs and studio monitor it's really noticeable.

Since I've discovered that, I've dropped these and bought a few of these USB isolators: https://hifimediy.com/product/usb-is...-high-current/
With the USB isolators, no more issues and the signal is perfect.

[RC Prime]

That isolator appears to just be a 5v dc-dc converter, i.e. a switch-mode power supply. You'll get the exact same ground isolation if you use a decent usb wall-wart/charger.

Separate supplies, no common ground, no loops.

[Lordbadgers]

Sorry to reopen.
I'm getting a hum that's a constant c#3 (yup I used my tuner lol)
I'm using the bluebox power supply but I am not able to get to a direct wall supply as I've literally got everything running of multi extensions from the only two sockets in the room.
Any easy ideas that don't entail paying an electrician to mount a new wall plate...?! Will that usb isolator work? There are a lot on amazon and they vary in price (!) but I don't want cheap junk...

That or I write everything with a distant drone in c#

[Steve]

Isolating the bluebox from a mass of devices will fix this. If you can share some photos of your actual setup we can make suggestions. We've all been there.

[Lordbadgers]

I can see the above hifime isolator on amazon. I'll try it. Can always send back

[Weazel]

As Steve says, we've all been there . I have a fully portable setup. My workaround is to use multiple batteries. For usb power, one of my favorites is GP Voyager 2.
I haven't had a single problem as long as I use as many batteries as possible in my setup.

[Steve]

It also depends on where you are located, geographically. In the US, I have little to no issues when using the proper cables and adapters. In Germany, for example (specifically at SUperbooth), I have a very different experience and use batteries as Weazel mentions above.

[kyhosco]

my solution: hum destroyer from behringer on all devices, its magic. costs 25,- EUR per box. its passive also.