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I picked up this amp on Monday. ( Orange OR15 )

running it through a single G12H-30 for now.
it sounds Great!
when i got it home i did notice some unwanted hum.

when the amp is on .. it's the usual tube amp hum.
BUT..
when i plug a guitar cable ( i've tried a few different cables ) the hum is much worse.
i took it back to get checked out.
the amp tech replaced the phase inverter preamp tube.
it does sound better now> the amp has more bite.
i've been playing for a few hours today.
BUT..
the static hum remains the same.

Before i took it in for service, i researched online.
someone posted about the same hum issue. and claimed to have fixed it by -
adjusted the amps

hum balance pot?

anyone have experience with this amp..
or adjusting hum balance pots??

That sounds weird to me, a hum balance pot?
Maybe they meant the bias pot, as in the amp might not be properly biased? (too hot I'd guess maybe)

isnt there like a ground lift pot or seomthing on it? I know my fender has a "hum balance pot" thing on it. i dont know the technical term for it, maybe someone else can chime in on it.

I don't know if your amp has one, but 70s Fenders had a hum balance adjustment in lieu of a bias adjust. The notion is that you dont need matched tubes, but simply adjust the proportion of bias voltage each tube gets, and the adjust is simplified in a push-pull amp because the hum is lowest when the bias balance is right. You can do bias adjust AND hum balance controls in the same amp, but I'm not aware of a manufacturer that does this.

Oh yeah, of course, aren't these amps cathode bias which means they usually don't have bias pots at all?
For what I know it could also all be down to the power amp tubes not being matched properly or one could have gone out a little or something along those lines.

i'm really not much of an amp tech guy.
i emailed Orange with the details ..

i know someone that can help me this weekend. i hope.
i do wish the tech had indicated if he checked anything balance/ bias related.

Have you tried it any place other than your house?
Could be that the amp and your mains power don't agree or that you are getting interference from radio or lights.

is it your guitar? my tele hums if i'm not touching metal (I KNOW. I'LL FIX IT EVENTUALLY) because it's not grounded properly. I AM THE GROUND.

i'm going to do that. thanks.
i've never had issues with any other amps doing this.
BUT - maybe the Orange is different.

i've had everything plugged in all afternoon.

so - once i shutdown. i'm going to setup again somewhere else in the house.

antennafarm wrote:is it your guitar? my tele hums if i'm not touching metal (I KNOW. I'LL FIX IT EVENTUALLY) because it's not grounded properly. I AM THE GROUND.

nah. it's for sure amp related.
i've been using different cables and guitars through it.

when i'm not playing .. i can just unplug the cable. or put it in standby.. and the hum is gone.

BUT.

it shouldn't be there in the first place.

If changing locations doesn't help, try putting a patch cable from the send to the return of the
effects loop (with no pedals in between) and see if that stops it.

i tried changing locations. still hum.

i tried patching the fx loop. i thought it worked for a moment but no.

i don't think it's a deal breaker. the hum is just annoying when sitting idle next to me.
and.. reading that thread about the hum balance/bias pot .. makes me wonder.

I just looked at the schematic and can tell you where the hum balance pot is if you are comfortable
in your ability to get inside the amp without killing yourself.

i don't feel comfortable.
but. a friend can probably do it. and show me.
I may try it myself. maybe.

the fx loop sounds nice on this thing btw.
el cap - wet - reverberator etc. all sound sweet!