Harley Benton Pa-100 issue

Stevepage

Using the PA-100 with my Triple Rectifier as a load box to use direct into my DAW. I took out 2 Power valves to reduce the power down to 100 watts (I was running at full power but volume down to 9 o clock on the amp) but I'm getting this persistent noise issue.

It sounds like a really annoying squeal and changes pitch wherever you sit. I've tried positioning the attenuator a certain way, re soldered a loose ground wire and still the problem persists.

Any one else had this issue? or heard of it before? It's becoming unusable

ICBM

If it changes pitch when you move the guitar relative to the amp then it's electromagnetic coupling from the OT back to the guitar pickups. It could possibly be from the load if it was reactive with a significant inductance, but if it's purely resistive that's not as likely as from the OT.

The only solution is to move the guitar away from the source of the electromagnetic field, or don't turn the amp up as far.

It's important to stop it, regardless of it being annoying - it's potentially harmful to the amp.

ecc83

ICBM said:

If it changes pitch when you move the guitar relative to the amp then it's electromagnetic coupling from the OT back to the guitar pickups. It could possibly be from the load if it was reactive with a significant inductance, but if it's purely resistive that's not as likely as from the OT.

The only solution is to move the guitar away from the source of the electromagnetic field, or don't turn the amp up as far.

It's important to stop it, regardless of it being annoying - it's potentially harmful to the amp.

Woah! Never had that IC but I can see it being entirely possible. Might help tipping the amp on its side to change the coupling relationship as we do to stop hum coupling?

I can think of a few mods I would try but of course would need the ministrations of an amp tech.

Dave.

ICBM

I first found it testing 100W Marshalls with a Powerbrake. I also forgot to say that it’s much worse with single-coil pickups, humbuckers mostly stop it.

Stevepage

Well I moved the amp and the attenuator further away and also switched from Bold to Spongy (which cuts power some what) and that seems to have solved it. I think it may have more to do with the Bold setting just being too much for the PA-100 to handle. Not the end of the world, still sounds great and I'm trying to move the Rectifier on anyways.