Parallel 6L6 SE Amp

[TIMBO]

Hi guys, I have a pair of mismatched ( different tube type)RCA black plate tubes that came out of the old Fi Sonic I restored and I'm not sure that they would have the same bias point or that you would use them in a PP amp.
A dual fixed bias circuit was discussed and the possibility they could be use with it.
 
Would a parallel 6l6 SE with an adjusted cathode bias on each tube to get then at a similar bias or a dual fixed bias on each tube.
Would it even matter if the tubes were bias different?

I know that out of one tube I could achieve 25-30w but I have 6l6 SE amps and its such a waste to only run one.
It seems that 30w SE transformers are about as big as they get. Thanks

[printer2]

You would not get 30W out of a tube, that is the plate dissipation not the power out. You might be in the 10W ballpark for a single tube. Having separate  cathode resistors will work, I would use a base value that was a little high for the tube and then adjust it down by putting a smaller wattage resistor in parallel with it. The theory is you might get a more complex sound out of two tubes if they are biased differently.

[kagliostro]

Ciao TIMBO

the use of separated cathode resistors and bypass cap sure will not be a problem



Franco

[TIMBO]

Thanks K.

[TeslaRect5150]

Hey Timbo,
   I'm working on a 2 x 6v6 push pull design right now that uses separate cathode bias resistors without any problems so far. I think some the THD brand amps do this. They can use a 6v6 in one socket and an EL34 in the other. That sort of thing. With the adjustable bias you're talking about it would be an awesome amp to try different tubes/bias in.
In my push pull cathode bias amp I did try using a 6v6 in one socket and a 5881 in the other. Just for the fun of it. Seemed to work just fine with the tubes biasing up different. The amp wasn't tested for a long period of time this way and sounded OK. It was odd to look at though. 
 My favorite amp is a SE 6L6 amp, although not the loudest amp at there, I love the tones it produces.

Peace,
Aaron

[TIMBO]

Thanks Aaron, I looking to do a Guitar/Harp amp and the 6l6 looks to be the tube of choice https://www.lonewolfblues.com/proj6l6se.html and having the two RCA's it just seem a waste to only use one.