Audible buzzing noise from CV ports


Am trying to resolve a buzzing noise heard thru monitors when plugging Pyramid directly into M-32 / DFAM, and while in Pyramid is in TRACK mode. The buzzing nose is only audible while in TRACK mode and diminishes significantly while in LIVE, STEP & SEQ modes. It’s very noticeable when working with low level ambient sound and while toggling tracks between mute and unmute.

The buzzing noise becomes audible after syncing DIN clock to Env Out. It also increases after loading a patch and it changes in both volume and frequency while LED Illumination mode is changed from default.

This only occurs in TRACK mode and because of such may discount this as some kind of a grounding loop. I’m leaning towards an internal issue with the Pyramid, maybe defective board, PSU, bad ground / isolation, etc.

Has anyone else experienced similar issue and how did you resolve it?

EDIT: I deleted this post due to recent troubleshooting efforts which would have exonerated the Pyramid. But since another forum member shared they’re experiencing similar issues I decided to retract it as it may help others.

As a simple test, when I disconnected the Pyramid from a shared powered-hub and powered it directly with a USB wall wart the buzzing issue disappeared. So either the powered-USB hub wasn’t providing enough power (amperage) to the Pyramid or there is indeed a grounding loop somewhere in my setup. Will continue to troubleshooting if I can’t function without USB connectivity. Right now all MIDI goes over the A&B DIN ports so I don’t believe USB connectivity is a requirement at the moment.

ground loop issue… very common with all devices that use usb.
in this case, you’re grounding thru the usb and thru the sleeve of the cv jack.

like you I found DINs are the easy (but inconvenient ) solution when it occurs (which is not always !?).
there are other solutions, if you search for ‘ground loops’ -usually variations on ensuring no loop on the ground by removing one of the ground connections.

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I had a similar issue that I attributed to the power supply (I feel like technobear’s response is accurate for that matter). I am in US and the power supply that came with my Pyramid had that buzzing sound coming from the cv outs.

My hacky solution was to have my USB power route thru a USB battery charger which in turn is always plugged into the power strip.

I would like to have a more robust solution, but what I’ve got works well enough.