Ground Hum - especially when using 2 or more outputs

Hello all,

My unit seems to fully work and sound great, however I noticed that I have a ground hum coming through the outputs... It's soft hum when I use 1 output, however, when I use multiple outs it gets very loud, also gets loud when I connect trigger out to another synth..

Has anyone noticed hum when using trigger outs or multiple outputs?

Dear Discodisco,

It seems like you have a ground loop. The Output ground come from JP3 Pin1. This is the only ground connection of the Jack Output. Ground isn't common between power supply and jack on the IO board.
Check that's what you get.

Best regards,
e-licktronic

Thanks for your reply Vincent,

I checked all of the connections, and for some reason the output jack(s) earth connection IS common to the power supply earth (the gnd connection on the +15/-15/+5/Gnd 4 pad connection)

I have checked and re-checked every solder joint for a short, and i cannot find one. The unit seems to work perfectly..

Would you have any suggestion that i should try? I suspected the master out cable (its earthed at 1 side only) but removing this did not fix the problem

Could you post a HD picture of the IO boards ? it's possible that you get a proto IO board who had this Hummmm problem.

The first one is the good one. Jacks ground plane and Power ground are separated.

: IO_Board_PCB_Top.png (18.28 KiB)
Viewed 9150 times

: IO_Board_PCB_Top_Proto.png (19.21 KiB)
Viewed 9150 times

Best regards,
e-licktronic

Thanks for your reply Vincent,

I looked at the circuit board very carefully, it looks like the correct one - I can't really get the photos to show clearly, but I will try again and post them up.

There is a separation in the copper between the earth plane (power) and earth plane (signal) as shown in the first photo you posted.

What else do you suggest i look for, assuming that I have the correct circuit board?

Cheers

Is the master section connect to the power ground ?
Do you get a scope to check what's happen in the ground ?
Is your wall wart PSU 1000mA 15v AC ?

It's not easy to solve ground problem but we will find an issue

Best regards,
e-licktronic

Hello Vincent,

I did some more testing:

I had already disconnected the Signal Cable from the Master Section to Master Out, this did not solve the continuity problem.

The Power Ground and Signal Ground seem to be having continuity from Pin 1 of J3. When i disconnected J3 from the I/O board, the Output Jacks were no longer having continuity to the Power Ground.

I noticed though, that the 10pin Jumper has continuity to Power Ground on Pins 3,4, and 10.

I suppose the good news is that the I/O board is okay? the bad news being the continuity is happening somewhere on the main board?

If you have any suggestions of where to look it would be good. I don't have a scope sadly, but if it is really necessary, i guess i could try and find one from someone?

My AC powersupply is 16v 1.37A

Thanks!

Hello All,

I finally got a moment to do some more testing - has anyone else experienced any earth hum problems?
Would really like to solve this asap as i have a recording session lined up soon!

Cheers

Hi Disco Disco,

did you ever sort that ground hum problem? I have the same problem you described and since I have started using the trigger with another synth *and* distrortion on the Yocto, the humming got quite annoying.

What helps is to use a Palmer Line Isolation Box ("PLI-01") -- when I put that in the main out (I rarely use the individual outs), the hum is gone.

I am using a 15VAC, 1000mA PSU with the metal enclosure created by ElStroumph.

I have the same problem, but only notice it when using the trigger outputs. If i trig another machine of any kind from the yocto, it gives a ground hum (the triggered machine). I havent exactly checked if the yocto gives hum when using multiple outs but havent really noticed anything in use - only with the triggers. Other than that it works and sounds great!

As discussed but unsolved here; viewtopic.php?f=16&t=228