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previous: Liam R.G.Thanks for the thorough... -- 11/10/1998 3:12 PM View Thread

Re: Bias Range Please

11/10/1998 9:10 PM
Jim S.
Re: Bias Range Please
I own one or two books (one of them is Tom Mitchell's "How to Repair Your Own Tube Amp") that recommend biasing EL34's at 55-60ma at idle (with no mention of taking the plate voltage into account)! Let's see, a typical 100W Marshall Super Lead puts about 500v on the plates, so that's close to 30 watts being dissipated per tube (5 watts over max). I wonder how many hundreds or even thousands of sets of perfectly good EL34's were prematurely cooked to death because amp neophytes (like I was when I first bought that book) followed Mitchell's recommendation to the letter.  
I guess for those guitar players that love the sound of "a Marshall about to blow up", there's no substitute for a Marshall that IS literally blowing up.

R.G. I've wondered how much a fan increa... -- 11/10/1998 10:29 PM