Express EL34 or 6V6
Moderators: pompeiisneaks, Colossal
Express EL34 or 6V6
I noticed that some of the Trainwreck express schematics say "EL34 or 6V6" next to the power tubes. Does this require a bias adjustment when you change between EL34 and 6V6? I would think that it does, but I have never built a Trainwreck Express.
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Re: Express EL34 or 6V6
It would, yes, from teh sample datasheets I grabbed for them,
6V6: Plate Current Zero Signal 70mA
EL34: Plate Current Zero Signal 55mA
If it was biased for EL34, then the 6V6's woudl be fine, just a touch cold, but they could be close to shut off? The EL34's into the 6V6 may redplate.
Of course you'll need to ensure pins 1 and 8 are tied together, an amp built for 6V6's doesn't need that, but for EL34's does.
~Phil
6V6: Plate Current Zero Signal 70mA
EL34: Plate Current Zero Signal 55mA
If it was biased for EL34, then the 6V6's woudl be fine, just a touch cold, but they could be close to shut off? The EL34's into the 6V6 may redplate.
Of course you'll need to ensure pins 1 and 8 are tied together, an amp built for 6V6's doesn't need that, but for EL34's does.
~Phil
tUber Nerd!
Re: Express EL34 or 6V6
Thanks for the reply. So far, every amp I have built has pin 1 and 8 tied together. Is there a case where you would not want to tie 1 and 8 together?
Re: Express EL34 or 6V6
6V6s and 6L6s don't use pin 1. Many Fender amps have the 1500Ω grid stopper resistor mounted directly on the socket between pins 1 and 5. You can see it on this 1964 Deluxe Reverb...
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Re: Express EL34 or 6V6
Thanks for the reply. That makes sense. It's the same as when I mount my screen resistors to pin 4 and 6 and attach B+1 to pin 6, only most if not all octal power tubes we use for amps don't use pin 6.
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Re: Express EL34 or 6V6
If you really wanted to use those tubes in that case, though, you could install a terminal strip to move the 1.5k to it and connect there for the input, and then tie 1 to 8. This is, again, only if you want to use tubes that don't internally tie 1-8 like the EL34.
~Phil
tUber Nerd!
Re: Express EL34 or 6V6
So far, I've built 4 amps with 1 and 8 tied together. I'll continue to do so until I find a reason not to. The only advantage I see to not connecting 1 and 8 is for the grid stopper between 1 and 5.
Mike
Mike