Problem with new studio Preamp :(

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FastRedPonyCar

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Last night I cranked up the studio for the first time. Worked pretty well. Tweaked around with it for about an hour and half. OOOLD power tubes in my amp I'm using the power amp from is probably contributing for the flabby mushy low end. I pulled the old preamp tubes out and put in new ones.

V1 - NOS RCA 12AX7
V2 - Penta 12AX7
V3 - Sovtek LPS
V4 - Groove tube 12AX7C
V5 - NOS Mullard 12AT7

Controls are smooth and the amp is loud volume wise and had no noise.

I bought the amp from "Themailmanpsycho" and he included a pair of mesa 6L6GC's. Used. I put those in this morning and switched on the amps and immediately got a very strong consistent electric squeal. Now, It's not the preamp tubes and what's odd is that if I unplug the guitar from the input jack, it goes to silence.

I didn't try plugging it back in and then unplugging the cable from the guitar to see if it still made nose and I didn't try removing the power amp and sending it straight to my mic preamp to my PC to see if it still made the noise.

And the noise is only on the lead channel.

It's not a microphonic squeal..like it's not a harsh and abrasive squeal like a preamp tube makes when it's microphonic (and I swapped all the preamp tubes and it still made the noise) It's a very steady solid EEEEEEEEEEEEEEEEEE sound...but what's wierd is that if I roll the guitar's volume knob down the frequency lowers in pitch.

I'm hoping there's just something wrong with the power tubes. That's the first thing I'm going to do when I get home but if that doesn't fix it, what could be causing this?

I played it for about an hour and a half last night with no issues and the only thing I've changed is those power tubes so I'm thinking this HAS to be the source of the noise but it's a new noise I've never heard before so I figured I'd ask you guys if any of you had experienced anything like this?
 
Hey Drew. I'm still getting to know mine so I don't have a ton of experience with it yet. But from what you've said, it seems the only variable was the power tubes. I'd bet that's where your issue is. I bet if you go direct to PC, you'll hear no squeal because you've removed the amp from the equation.
 
I think it was some wierd grounding issue.

It still made the noise when I unplugged it from the power amp becuase I could actually hear it in the preamp itself. When I turned the amp off and put the top cover back on, it was quiet again.

Hmm..
 
FastRedPonyCar said:
I think it was some wierd grounding issue.

It still made the noise when I unplugged it from the power amp becuase I could actually hear it in the preamp itself. When I turned the amp off and put the top cover back on, it was quiet again.

Hmm..

Oh, OK. If the top was off that would explain alot. I experienced similar noises when I realized it was because I had the unit on the floor with the Boss DD-20 sitting right next to it. I think the in/out cables and power cables were a bit tangled up too at the time.

Digging the preamp?

Dave
 
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