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Title: Where is the bias pot located Post by: Relicula on April 24, 2008, 02:18:36 AM I havent opened it up yet, but there are three trim pots inside from my understanding, fet, od, and phase inverter, where then would the bias pot be?
The od sounds thin, and anemic, nothing fat about it, must begin the tweaking process I guess. Title: Re: Where is the bias pot located Post by: ChrisL on April 24, 2008, 02:24:12 AM The pot is accessed via flat head screw driver from the outside of the chassis between the power tubes.
Title: Re: Where is the bias pot located Post by: jzucker on April 24, 2008, 01:46:25 PM The pot is accessed via flat head screw driver from the outside of the chassis between the power tubes. Mine doesn't require a screwdriver. It's just a shaft (no knob) sticking out of the bottom. Very convenient to adjust. By the way, mine was biased at 42ma from the factory using tungsol str 6L6 reissue tubes. Anyone think that's a tad hot? Title: Re: Where is the bias pot located Post by: JohnE on April 24, 2008, 03:28:43 PM As ususal, people seem to have definite but varied experiences that are at odds.
Here's mine: I am player, not a hobbyist, but I believe in doing basic maintenance on my gear. I read the articles on biasing and adjusted my amps accordingly. 42mA is right at the range of a "hotter'" bias, but within the "70%" recommended. I think you could get up to 45mA or so depending on your plate voltage which is the other part of the equation. Now the counter: I have a great amp tech who does all the serious work on my amps. He insists that a lower bias is better and it does not effect the tone (I know, I know, the argument will start now). He says the tubes will last longer. I have done the bias comparison on my Bassman and Super Reverb and I have to admit, that he seems to be right. Since both these amps run 6L6 tubes and plate voltages 450-470 which is similar to the Overtone I think the same settings will work. My amp tech sets them up at 25-30 mA (brrrr cold). They sound great to me. Matched tubes (+- 5mA, preferably less) seem to be much more important than bias, especially at higher volume. Try lower the bias and let us know what you think Title: Re: Where is the bias pot located Post by: jzucker on April 24, 2008, 06:55:31 PM I already lowered mine to about 35 but was thinking of going to 30ma. That's what I was setting my fender amps to. I might try EL34s in it too...
Title: Re: Where is the bias pot located Post by: JohnE on April 25, 2008, 02:39:08 PM When I replaced the transformers in my super reverb, I had it set up for EL34s. I learned that the circuit has a lot more to do with the tone than the output tube. Ialso found out that I liked 6L6s a little better, but we better start a new thread if we get going about tube choices.
Title: Re: Where is the bias pot located Post by: hywelg on April 25, 2008, 07:02:53 PM Jack I'd be very interested to hear your thoughts on the tone/breakup when lowered to 30mA. My tech set mine to 35 from the start saying that was the recommended setting for the 6L6. I was going to try 38 in a while when I've had a good play with it at 35, but maybe I should consider going lower instead.
Thanks Hywel Harris |