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Old 8th Apr 2021, 7:34 pm   #3
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Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 6,166
Default Re: Mullard 3-3 voltages query

Originally Posted by ms660 View Post
Originally Posted by qualityten View Post
Is the disappearing sound a useful diagnostic symptom?
That sounds like it might be turning into an oscillator.

Lawrence.'s a common thing with these amplifiers since the wiring layout is quite critical. It's probably going into supersonic (you can't hear it) oscillation. The EF86 is running in 'starvation' conditions and the gain is very high. This can result in supersonic oscillation through poor layout or long runs of wiring.

These really are excellent little amps (I've built three in the past) but you really need to be careful with layout and follow the Mullard wiring as closely as possible.
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