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Author Topic: Motor Boating?  (Read 3891 times)

lefizz

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Motor Boating?
« on: October 30, 2007, 06:35:39 AM »
My amp setup uses a 100 watt class T amp and the TL071 based preamp many people here have help me with.

The issue is this, at high gain setting, i.e. when i want to play loud, the amp ocassionally gets stuck it a sort of weird feedback loop with the Bass driver pumping in and out slowly with no input from the guitar. Is that called motor-boating? Even totally dampening the strings doesnt stop it, the only way to control is it to either turn of the amp or cut the volume right down for a moment.

I was wondering what causes this and what could be done to reduce/eliminate it.

Any feedback(no pun intented!) greatfully recieved.

Phil

LJ King

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Re: Motor Boating?
« Reply #1 on: October 30, 2007, 11:32:31 AM »
Motorboating is almost always caused by a low frequency feedback path through the power supply.

Increase the value of the power supply decoupling caps, or replacing old ones that have lost some capacitance usually corrects the problem.


joecool85

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Re: Motor Boating?
« Reply #2 on: October 31, 2007, 07:46:48 AM »
Motorboating is almost always caused by a low frequency feedback path through the power supply.

Increase the value of the power supply decoupling caps, or replacing old ones that have lost some capacitance usually corrects the problem.



I would try replacing the old caps first, electrolytic caps only last for 15-25 years anyway.
Life is what you make it.
Still rockin' the Dean Markley K-20X
"New" amp: Fender Frontman 25 DSP (FM25DSP)
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