Bassman distortion issue

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Bassman distortion issue

Postby boola on Thu Apr 06, 2017 7:57 pm


My 65 Bassman is producing a distortion that sounds like mild speaker rubbing. The note is still there but with this extra mild distortion. It only occurs when certain frequencies are played, seemingly centred around A.

It sounds so much like speaker rub that I tried a different cab just to be sure that wasn't the problem.

I think it has always been there but is possibly more present now. Please can anybody suggest what might be causing this?

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Re: Bassman distortion issue

Postby tubeswell on Sun Apr 09, 2017 6:33 pm

Could be mechanical vibration affecting the tubes, or it could be something electrical, like failing filter caps causing loss of power supply decoupling between HT supply nodes in the power supply rail, or failing filter caps in the bias supply, or a loose tube socket pin clamp, or a loose/improperly-closing input jack tip switch contact etc etc. Hard to say without getting more detail.
He who dies with the most tubes... wins.
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Re: Bassman distortion issue

Postby stratele52 on Mon Apr 10, 2017 10:18 am

+ 1 tubeswell

2- Both channels ?
3-Try another guitar
4-Check tube, best is to try new good tubes.
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Re: Bassman distortion issue

Postby Unit_1 on Mon Apr 10, 2017 9:55 pm

Had the same thing on my 4x12 cabinet

There was a strip of paper, being held in place by fuzzy dusty spiderweb crap, and when I would hit a deep note the force of the air blowing under the cab would make the paper flip back and forth quickly. :huh: Almost sounded like a bird flapping it's wings, but super fast.

Another time I found one of my shaker eggs had fallen into the recess for the handles........

All kinds of crazy things can cause those spurious annoying sounds.....
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