Marsha making a high-harmonic noise...

[FAN HALEN]

Hello,

I have a Friedman Marsha amp and I'm getting a high frequency harmonic sound when I hit a power chord (it's faint and you have to really listen for it but it's there and it's driving sound guys crazy). I believe it's the first preamp tube (from left to right) that's giving me the problem because when I flick it there's a high pitch noise coming from it through the speakers (all the others don't do this). I replaced the tube with several others (in fact I replaced all the preamp tubes) and I'm still getting this high harmonic noise.

Dave or anyone else have an idea what is causing this and is there anything you can suggest I try to get rid of it?

Thank you!

-Derek
http://www.fanhalen.net

 

[boneyard]

Its probably microphonic tube ... aka getting bad. Just replace it with another 12ax7 and you should be good to go. If you tap it while its on and it starts to whistle, thats a sign its gone.


I'm sure others will chime in to

Good luck, Matt

 

[FAN HALEN]

It's not a continous harmonic ring. It only last for a few 10ths of a second after I hit a power chord...see video. Thank you!!!

 

[charveldan]

Get rid of the JJ tubes and replace with Tungsol.

 

[racerevlon]

You playing a Strat? It may be your G string ringing out after mute due to no string tree. Try stuffing toilet paper under the strings behind the nut and see if it goes away.

 

[Scumback Speakers]

It's not a continous harmonic ring. It only last for a few 10ths of a second after I hit a power chord...see video. Thank you!!!

Is the amp head on top of the cab? If so, move it off there and try it again. If the noise goes away, it might be getting a vibration from the cab that rattles V1 in your amp head. If it's still there, I would try putting a piece of foam (or a bath towel) under your head to isolate it from sympathetic vibrations.

 

[RACKSYSTEMS]

What Jim said. It's a microphonic tube. Almost every tube these days is microphonic. Just bring it by my shop and I can straighten you out.

 

[Trebor]

Hi, long time lurker, 1st time caller.....I just got my BE, & I'm having the high pitch ringing, except mine stays constant , I'm going to replace the pre-amp tubes, & hopefully that will take care of it.....Other than the ring, it sounds awesome......I'll be back!

 

[Trebor]

All good!....I put in some Nos Siemens, & this is thee tone, & no ringing(Except my ears) ......Killer Amp with a Scumback 4x12 loaded with Blackback 65 watt'ers, Thanks Jim.......Thanks Dave......