Ground loop or buzzing Hermod at high gain


Was wondering if anyone could test this for me.

  1. Hermod powered in a case, nothing plugged into Hermod.
  2. Line out of any VCA or Mixer within the same case into an audio interface. (no audio plugged into VCA or Mixer)
  3. Audio interface gain turned way up.
  4. Digital buzz and humming from the Hermod that changes character depending what mode you are in.

Just wanted to see if anyone else gets any noise, typical recording levels of a source mask this noise because the audio interface gain is never turned up high enough to pick it up, but it’s still there.

I’ve tried multiple cases and power supplies, I have surge protected power bars and have put all interfaces on the same power brick.



I wonder why squarp ignoring so much issues with ground bleed?!

I don’t think they are ignoring, if you contact them directly they will be happy to try to help you out.
But I’d assume it’ll be a hardware issue so I doubt they can fix it ( except with hardware revision)

Digital noise is not uncommon in racks with more complex digital modules , partly because eurorack is a simple ‘standard’ that does not try to avoid noise.
it’s also highly dependent on your setup,
so its much worst for some than others (hence why not everyone is complaining about it).

Personally I’ve not had many issues with it,
except some ground loop noise occasionally when connecting the pyramid via cv - usually with a bit of messing about I can then get rid of that.

I have contacted Squarp and they said they could take a look at my unit, I haven’t sent it in yet because from what I’ve read this may be likely the units interaction with switching power supplies and the module being digital.

From my research online, it would appear if I had a linear power supply this issue may be remedied. It is quite annoying however on both the MakeNoise and Doepfer PSU3 there is a quiet ground loop being created and changes frequency depending on how many LEDs are lit on Hermod. When the modular is emitting sound this is masked to some degree. But when I have no sound playing on a patch and I bump up the gain quite high on my audio interface or mixer there is a high frequency ground loop type noise sitting in the background Removing the unit from my case and the noise disappears.

I would be curious if other people with switching supplies could test this with a patch connected but no sound playing with their interface gain increased to see if they experience the same issue. This would help me determine if I should send my unit off.

1 Like

I have the same issue. It’s most noticeable when patching between my IJ Palette and 7U (both switching PSUs).

Hello guys,

We found a software fix that will be in the next hermodOS version, soon to be released, improving a lot the noise amount!

To provide full transparency, we never experienced by ourself this problem with Hermod (unless with a cheap power supply) and according to users, it seems quite rare. But thanks to some users of this forum we were able to find and fix the issue.

We know that ground problems can be really tricky to troubleshoot. I take advantage of this message to list here some advices, helping you to reduce the noise of a module:

  • try to change the module position in your eurorack case
  • do not screw the module to see if it reduces the noise, or maybe use plastic screws
  • try an other 15V power supply adapter
  • try an other case (or an other 12V/-12V/5V power board)
  • try an other power outlet in your studio, without using outlet power strip
  • use a linear power supply (the best way to get rid of noises)
  • if the problem appears only when you use the USB HOST, use a special Y usb cable that power your usb device with a separated supply

Have a nice day, and stay safe!