Which O.T.

[tonelab2]

Which output tran for 50watt model.
6800 primary or 3400 ohms?

[llemtt]

Try 4200-4000 (Fender bassman values) but also 3400 is good, if you go higher you have to increase also plate voltages otherwise you can't obtain 50w (rms) with just two 6L6.

I am actually using 5000 ohm and ˜410 volts on the plates under full load and power output is only 35w (rms) at clipping.

Teo

[jaysg]

For a new 50W build, use either a 50W Plexi OT for EL-34s or a good 40W Fender 2/4/8 universal OT for 6L6s. I suggest the Allen TO2/4/8.

[oldmacman]

For 50W 2x6L6, I've used Weber's larger 40W 2-4-8 transformer and Hammond's 60W 4300 ohm transformer. Both worked well.

[dobbhill]

How about an old Dynaco 4300 ohm tranny from a Stereo 70?? Would it work with 6L6's, or should I stick to EL34's? What about a MKIII (70 watt 4300ohm) output ?
Thanks, D

[tonelab2]

Thanks for the reply.
O.K. just to really muddy the waters, how about 4 x 6v6s? what primary for these . Will push 45 watts with maybe a switch to kill 2 tubes for 22watts.

[Moose]

Quad of 6v6 would be fine around 4-5K, depending. Use a TW tranny, 36watter tranny, or anything else in that range good for 40W. Run 'em around 400-415V like a Deluxe and expect to use only really good tubes, especially at lower primary impedances. You'll have twice the poweramp of a BFDR, so power will be in the low 40W range.

Any of the trannies listed here should be fine for that, or go with the Heyboer TW trannies, 36Watter trannies, etc.

Since my liverpool/18watt/36watt experiments, I have secretly harbored the idea that using a quad of tubes has some smoothing benefit in the poweramp compared to a pair, so I've been considering a 4x6V6 amp for a while, now. I don't know if this would matter as much in a Dumble style where the poweramp overdrive isn't pronounced like on a 'Wreck, but I'll do it somewhere, eventually.

[glasman]

I have been using the MOP-50 Marshall replacement transfomers from CE. They measure around 3400 p/p and I get about 48 to 50 watts measured out at 455 to 460 volts. I have several heyboer 50 watt marshall replacements that I have tested and they looked really good as well.

Actually the best sounding clean in a D-style I ever built was using a set of trannies for a Sovtek MIG-100. That transformer measured 2400 p/p and the amp puts out exactly 100W at a plate voltage of 535 volts.


Gary

[glasman]

Thanks for the reply.
O.K. just to really muddy the waters, how about 4 x 6v6s? what primary for these . Will push 45 watts with maybe a switch to kill 2 tubes for 22watts.

I was actually thinking about a 3400 with the 4x6V6's. At about 440v. JJ's are a neccesity at those voltage levels. And they soung good.

Gary

[llemtt]

I am running EH 6V6 at about 420 and they are fine, never tried higher voltages but with screen resitors 1k or more it shouldn't be an issue, Jim Kelly builds amp with much higher voltages on 6V6s.

Going to try JJ's too!

Teo

[Funkalicousgroove]

FWIW I've had those JJ 6V6's dissipating 20W at idle with 450V on the plates and they don't so much as red plate-Good Tube for sure!

[Moose]

I am running EH 6V6 at about 420 and they are fine,

Going to try JJ's too!

JJs are great and in the trainwreck and deluxe circuits (the only ones I've tried both in) I prefer them to the EH for tone.

What's cool about EH and JJs both is that you can cram them in a BFDR or similar, which can see anywhere from 415-440V on the plates, and they'll be cool. That's way out of spec, and even more so since they were designed for 410V at 115V coming out the wall, not 120 or more like we have now. I've never killed them and they both sound good.

As for the screen resistors, the problem with high voltages and just slapping on a bigger screen R is that, if that R gets too high, you can start sagging the screen voltage enough to really notice. Whether this is good or bad for the tone and feel is a matter of taste, but the difference of a couple of watts is likely to be less audible than a sagging screen.

Anyway, the point is that even an AB763 circuit only uses 470 ohm screen Rs, so going higher with only 420V isn't necessary. If you do it to be able to run even higher plate voltages for the sole purpose of more power, it also might not be worth it. If you really need 5 more watts, crank the voltage and use 6L6. If you need more than that, use KT88 or a quad of EL34s and do the 100watt marshall tranny thing.

I may be wrong, though, in that Dumbles aren't really poweramp-overdrive sorts of amps like trainwrecks, so they may not push the screens hard enough that the feel will be affected.

All just food for thought.

[Funkalicousgroove]

I've used 1K 5 Watters on all of the ones I've built, But I also ground pin 1 as well so I can just pop in EL34s if I want and re-bias.