Microphonic Noise with gEQ

[fuzzgod]

All,

I'm getting a microphonic squeal in Ch3 MkIV mode. It happens when I have the gEQ on if I push the far right slider (highest frequencies) too far up. Settings on channel (bass, treble, etc.) all around noon.

Any ideas where a problem may be? I suppose I can always keep that slider low enough, but I know I've pushed it higher before without noise. Guessing it's a preamp tube. Any ideas which?

I'll Mesa a call and see what they say. Post a response.

Cheers

 

[MesaManBoogie]

All,

I'm getting a microphonic squeal in Ch3 MkIV mode. It happens when I have the gEQ on if I push the far right slider (highest frequencies) too far up. Settings on channel (bass, treble, etc.) all around noon.

Any ideas where a problem may be? I suppose I can always keep that slider low enough, but I know I've pushed it higher before without noise. Guessing it's a preamp tube. Any ideas which?

I'll Mesa a call and see what they say. Post a response.

Cheers

is the bright switch on?

 

[Barry]

Thats almost has to be a microphonic 12AX7 . I had the same issue and it turned out to be just that .

 

[fuzzgod]

Yep...it's only happening when the Bright switch is on...interesting...

 

[MesaManBoogie]

Yep...it's only happening when the Bright switch is on...interesting...

I had the same problem at one time, that was the reason I mentioned that.

 

[HeadlessAxeman]

To determine..if its a microphonic tube or not..pull out all the connections....keeping only the speaker load on..switch to Hard Bypass on the FX Loop Switch on the back side...and then see if you get the same squeals...

If you dont...there is nothing wrong with the amp..its just the signal chain/feedback gain(perhaps?)

The above solution is correct - since I had feared the same and gotten in touch with Mesa and a Mesa Techinician walked me through the above steps.

 

[fuzzgod]

Yeah, I did that...no guitar plugged in, no nothing. It only happens on MkIV and Extreme (not MkIIC+) with the Bright on and the gEQ slider up too high (~75% max). I'm gonna have a local Mesa repair take a look at it and see what they say.

Thanks all.

 

[fuzzgod]

Just a follow up in case this helps anyone...

Had Mesa-Authorized repair take a look at it (and they got Mesa on the phone) and it turns out that CH3 with max volume, Bright switch on and max treble (with slider) will cause squealing...haha, jeez ya think :lol: !!!! I figured as much, but just wanted to have it checked out and make sure there was nothing wrong with my baby. Come to think of it, I would never play with the amp setup that way, so I'm not sure how I stumbled on this one.

So take my advice, don't use the bonehead setup described above.

Cheers!