Strange noise from speaker cabinet

Hi all,

I was playing the other night and i noticed that i have a pulsing sort of pop noise coming from the cabinet. It doesn't get louder or softer as i turn the volume up or down. I have Strymon TL and BS in FX loop. At first i thought it might be something in the tap tempo causing it so i disconnected them and the sound is still there. Then i disconnected the entire pedal board (volume, wah, distortion, EQ, WMI, FSM) popping still there...

Only when i disabled the FX loop button on front of amp did the noise go away. Very strange. Thoughts as to what may cause this? thanks in advance!

Tony

Missed this for a fair while Tony, my apologies, the GM36 forum is a little barren and neglected nowadays I'm afraid.

The first thing I would check is to try to replicate the problem in a different location, and I mean a different building in a different area if possible.  It may be a power supply related problem, mains borne interference breaking through for example which can be your household items but also industrial gear nearby, and this would help to rule that out.

If it's only there with the Fx Loop engaged then it definitely points to that area as a cause.  Try putting in a short jack lead in the Send and Return, a short 15cm patch lead for pedals is best, and see if it still does it.  That way you are engaging the loop but with nothing of any influence in it.

Also try just putting the patch lead in only the Return and not the Send.  That way it should engage the switching on the Return jack to cut off the signal from the preamp so don't worry when it becomes silent signalwise.  Touching the tip of the exposed plug should generate a buzz of course.  Does that remove the pop?  If it does then we know the problem is in the circuitry before the loop and if it doesn't it must be after it.

Give that a go and let us know what you find.

Yeah it is a bit empty here ....
I'll give your suggestions a go and see what happens. thanks for the tips!