Power Supply - Strange Noise Issues

[Slade]

Hi,
I have some strange symptoms with my PS.

It's a Tonepad's Power Supply with LM317 and a 12vac transformer:
http://www.tonepad.com/getFile.asp?id=111

I have noise all the time from the PS, either being On or Off.

- When the PS is off, if I connect a DC plug to a pedal there's a "brrrrrrrr" kind of noise.

- When the PS is on, the noise gets bigger and more like a "buzz".

- If I disconnect it from the wall the noise is gone.

Anyway... All that happens when I use this kind of DC Plug:


But when I use this one the noise is almost entirely gone!


I'm really confused with all this....

Do you have any sugestions?

Thanks,
Fernando.-

[richon]

GROUND LOOP!!!!


instead of lifting the ground, try the "back to back" diode trick!!!!

[wavley]

Are you talking about a mechanical noise that you can hear without an amp (poorly laminated transformers will buzz and hum physically)

Or is this brrrr and buzz coming through the amp?

You can't ground lift a DC circuit anyway if it's a ground loop, there are other ways to get rid of it.

[Slade]

Are you talking about a mechanical noise that you can hear without an amp (poorly laminated transformers will buzz and hum physically)

Or is this brrrr and buzz coming through the amp?

You can't ground lift a DC circuit anyway if it's a ground loop, there are other ways to get rid of it.

I can hear it through the amp, that's the problem

[Slade]

OK, solved.
It was a Ground Loop. I tried richon's tip putting 2 anti-parallel diodes between house ground and PS circuit ground (ground lift). That totally solved the problem

Thanks a lot, richon!