Re: Bias problem



Pete wrote:

With JJ6l6gc i had 470 plate, -44 bias on pin 5, 42.5 mA for about 19.74
watts static and it sounds kick ass with a stock 6100 setup.
What tube are you referring to in the above? I have always been under the impession
that in order to run EL34's in a 6100 you HAD to modify the bias circuit.
Is this true or just horse shit?

I've seen reports from others who have been able to get them in range without a modification to the circuit. I'm not sure about mine as I haven't had it from new and I originally took it to someone to convert but I believe he just set the bias from what he said later and the fact that he didn't change the screen grid resistors. With 6L6/5881s, the maximum negative bias potential gives around 15W static dissipation and I've can get EL34s in range easily. I found 6L6/5881s sound better at around 22W static and EL34s at around 15W.

I'm using Harma '5881's at the moment, the early button base cold war era valve before the Sovtek label was put on them. They even have the Russian part number on them in Cyrilic writing. These are military stock and sound better than the later Sovtek '5881's. They're a good valve for heavy metal but don't sound as complex as other valves. They do respond well at low volumes, though, and it's easy to tell that the 6100LM was designed around this valve as other types make it difficult to get the balance right between overpowering bass and not sounding full enough.

When I replace the KT66s I tried with some Tung Sol 5881s at the weekend, I'll be interested to see how they sound.
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