Noisy signal while sequencing and recording eurorack

First the signal flow:
OP-1 sending midi to OPLab via USB Host A
OPLab sending gate & 1v/oct to modular
Modular output to OP-1 line input

I'm noticing a significant amount of noise at times. Whenever the OP-1 is on page 1 of the synth engine, all is quiet. When I switch over to other pages (ie. sequencer) a rapidly pulsing noisy pattern becomes audible. The pulsing behavior changes depending on the current page, some are quieter than others. If i pull the usb plug it goes silent. If i pull the line-input it goes silent. Some sort of grounding loop issue perhaps?

Has anyone else experienced this? Any tips, or troubleshooting ideas?


Hold shift and press the album key to go into options. One of the options allows you to disable usb charging if that seems to be one of the sources of noise.

Ah yes, I forgot to mention that I have charging disabled already.

I don’t know why changing pages would play a role in this unless it is because the input source is muted on certain screens. Could it be drive settings amplifying any already present noise? Sadly I always seem to detect some noise while recording directly into the unit, but these details can often be hidden in a mix. If you’re after pristine recordings of an unmixed source, you might just not get what you’re after.

sometimes i notice the noise too, i just try to use it to my advantage. it sounds amazing w/ the drum sampler actually. swell of noise after the kick slaps. ooooooooeee baby

I’m positive no settings are changing. If I’m on the “synth engine” page 1 menu it is an acceptably quiet, clean signal. I can play the op-1 keyboard, triggering the modular, everything sounds great. If I hit the “sequencer” button (not even playing a sequence, just moving to that menu), suddenly a fast pulsing digital noise becomes present. It sounds as if some communication via usb has been activated. Nothing else changes. So strange.