USB noise - cheap solution!

[Ilgrazza]

Xavier

I love my PreenFM2.

I had a slight issue with ground loop noise when using usb power; this is reduced, but not eliminated when using the 9v PSU.  However, I found a cheap solution by accident - the noise disappears when the Preen is connected to the PC via an old KVM switch (£5 from Ebay).

[Xavier]

Thanks for the info 

When you power with a PSU AND plug the USB to a computer, did you remove the JMP2 jumper ?

Removing the JMP2 will prevent using the power from the USB.
If you leave it you have current from both the PSU and the computer coming in the preenfm2 which must be avoided.

Xavier

[Ilgrazza]

Xavier

Thank you, I didn't know that - my Preen was built for me.  I removed the jumper and the noise is fully eliminated.

Keep up the excellent work!

[mzero]

Just leaving a note for others that might be searching up this topic:

This approach also worked for me: Remove Jmp2, then use the PSU for power, and USB just for MIDI - removes all the noise I was hearing on the audio outs when I was using just USB alone for both power and MIDI.

My unit is a van daal built unit, but it wasn't too hard to open it up and remove the jumper.

[hipelcanel]

Hi just to report that removing Jmp2 did not work for me..

When i removed it,  it made a pretty nasty and loud peak around 10k.
unit is van daal build

any idea why ?

[served]

Hello.

JMP2 doesnt remove the Ground issue. It only removes the USB +5V noise.
You might have a noisy ground.
Or you might have noisy PSU.

In my setup. If I connect USB to PC and Use External power. I get noise because my ground is not correct.
Mixer has lifted ground. So all the grounding goes through the PC USB cable. That creates a Ground loop.