What would cause a low key static noise in an amp at idle?

War_in_D

War_in_D

Well-known member
I've already tried cleaning all the tube sockets, along with all the 1/4" input/outputs. Tried different power tubes, and swapped around the preamps tubes to see if there was a noisy tube in V1. Happens with a guitar cord in the amp, or when it's not so I don't think it's anything external. I've also tried it on different outlets in the house. No change. Don't really notice it right after the amp is fired up, but then shows up a little bit later. Maybe within a minute or two. Can't hear it when playing, only at idle.
 
I've become an expert in noise :D
Now my rig is about as dead quiet as you can get (with two amps cranked mind you).
When you say you swapped around preamp tubes did you actually replace with a known good one?
I use a JAN Phillips 5751 specifically for this test (in V1 or V2). I do because it is a NOS low noise tube.
In other words, swapping the same tubes into different slots does not always give you what you want.
Lastly, if you think you may have a ground loop issue, there are some things you can do there (both cheap and expensive) to eliminate it.
What amp BTW?
 
No, I just swapped the V1 for one further down the chain. I wanted to do what you're talking about, but it's a Dual Rec and to get to the preamp tubes is a PITA. I'll have to pull the amp from the chassis though, and try that. I've got some NOS 5751's here too. I'll try one of those.

I don't think it's ground loop related, it's not that kind of noise and I can plug any of my other amps in and they are quiet.
 
War_in_D said:
No, I just swapped the V1 for one further down the chain. I wanted to do what you're talking about, but it's a Dual Rec and to get to the preamp tubes is a PITA. I'll have to pull the amp from the chassis though, and try that. I've got some NOS 5751's here too. I'll try one of those.

I don't think it's ground loop related, it's not that kind of noise and I can plug any of my other amps in and they are quiet.
Click to expand...
A Dual Rec. I just bought one :D I know it is a PITA. I have a Single Rectoverb now. PITA but worth it for something like this. My opinion is that 80% of the issues people have are actually preamp tubes. Seriously doubt it is the capacitors.
 
311splawndude said:
I've become an expert in noise :D
Now my rig is about as dead quiet as you can get (with two amps cranked mind you).
When you say you swapped around preamp tubes did you actually replace with a known good one?
I use a JAN Phillips 5751 specifically for this test (in V1 or V2). I do because it is a NOS low noise tube.
In other words, swapping the same tubes into different slots does not always give you what you want.
Lastly, if you think you may have a ground loop issue, there are some things you can do there (both cheap and expensive) to eliminate it.
What amp BTW?
Click to expand...


DING! DING! We have a winner.. Looks like it's a noisy preamp tube. I grabbed one of my NOS GE/JAN 5751's and stuck it in V1, and it made no difference in the static (but killed the gain). Stuck it in V2, reduced the gain but it was quiet. Figuring I had found the culprit, I moved the tube in V2 to the PI spot (figuring a bit of a noisy tube could work there) and stuck the PI tube in V2 and it was quiet, for a few minutes then the static started creeping back in again. So, being impatient as I am and figuring there may be more than one noisy tube in the mix.. I took all the Mesa branded tubes out and put five Sovtek 12ax7's that I know are good in there and it's dead quiet. Well, as quiet as a Dual Rec can be at idle on 100w in the vintage and modern settings on channels 2 & 3 at a volume loud enough to move my pant legs. Clean channel is pristine. Not to mention, I think it sounded better with the Sovteks in there.

My wife never complains about how loud I play, but when I shut everything down the TV in the living room upstairs was loud enough that it sounded like it was down here in the basement with me. I guess she was having some trouble hearing it. 😎

Thanks for the input everyone!
 
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:LOL:

Glad you got it sorted. I'm slowly building up my preamp (and power) tube stash for things like this - but I have nothing compared to some people on here :yes:

Recently got some JJ EL34 IIs and some Sylvania EL34Ls for something different. Have you tried EL34s in your Dual? I think I prefer them. A bit more focused and less bloaty. Subtle though.
 
311splawndude said:
:LOL:

Glad you got it sorted. I'm slowly building up my preamp (and power) tube stash for things like this - but I have nothing compared to some people on here :yes:

Recently got some JJ EL34 IIs and some Sylvania EL34Ls for something different. Have you tried EL34s in your Dual? I think I prefer them. A bit more focused and less bloaty. Subtle though.
Click to expand...

Yeah, some folks on there have massive tube stashes. I've got a very modest one, but it contains some pretty cool old vintage preamp tubes (Telefunken, RCA, Siemens, etc.). I keep the vintage tubes around for the less "complicated" amps, mainly my single channel hand wired stuff. I usually stay with current production power tubes though in all of them.

I have tried EL34's in Mesa's in the past but it's been a while, and not in any of these current amps I have. I've got a quad of Mesa EL34's in the stash, I might try them out before I put everything back together. They should bump the midrange a bit.
 
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