glasman wrote:
Well I periodically pull one tube and outside of lower output and earlier distortion the tone remains about the same.
Gary
Is there any risk to damage e.g. the OPT when pulling one tube and trying to get some power amp distortion from the other power tube?
Would it be possible to install a push-pull/SE switch in a 2x 6L6 amp by e.g. lifting the cathode of one of the 6L6s (or alternatively ground the cathode via a 10k)?
glasman wrote:
Well I periodically pull one tube and outside of lower output and earlier distortion the tone remains about the same.
Gary
Is there any risk to damage e.g. the OPT when pulling one tube and trying to get some power amp distortion from the other power tube?
Would it be possible to install a push-pull/SE switch in a 2x 6L6 amp by e.g. lifting the cathode of one of the 6L6s (or alternatively ground the cathode via a 10k)?
Best regards,
Markus
I know that some blues guys like to pull one of the output tubes (the one the farest away from the input), but I don't think it is healthy for the OT.
1) You could consider installing a triode/penthode switch which will reduce the output power by appx 40% and make the sound a little browner.
2) Another alternative is to have a switch in the FB loop. Opening the loop will produce a much looser bottom end and a bit more bluesy output section distortion.
3) The best alternative IME is to use a power soak to take the output down -3db or -6db. You only need a couple of power resistors in a small metal box to do this.
4) Even better - why don't you build a small champ clone or one of the versions in the beginning of this post.
bluesfendermanblues wrote:
I know that some blues guys like to pull one of the output tubes (the one the farest away from the input), but I don't think it is healthy for the OT.
1) You could consider installing a triode/penthode switch which will reduce the output power by appx 40% and make the sound a little browner.
2) Another alternative is to have a switch in the FB loop. Opening the loop will produce a much looser bottom end and a bit more bluesy output section distortion.
3) The best alternative IME is to use a power soak to take the output down -3db or -6db. You only need a couple of power resistors in a small metal box to do this.
4) Even better - why don't you build a small champ clone or one of the versions in the beginning of this post.
Thanks a lot for your explanations!
The easiest probably would be to install a triode/pentode switch. Might give it a try.
I also wouldn't have a good feeling when just pulling an output tube. On the other hand, it would leave one half of the OPT primary unconnected.
Why might it damage the OPT?
This thread is about single ended amps, Gary was talking about a Parallel single ended amp, not a push pull amp. This will cause an impedance miss-match like going half power in PP, but if you address the speaker load it's no problem. That's why it would be nice to have multi secondaries on a PSE amp. For single ended you need a gapped transformer made for single ended use, you can't use a PP tranny unless it's way oversized or you're in danger of core saturation.
I would venture to say Power soaks have killed way more OPT'S than pulling tubes.
We're not talking about running a PP amp on a single output tube. (What's the sound of one hand clapping?)
Personally, I don't think there is any reason to build PSE over SE. If you can play along with a drummer with 10-12 watts you need a new drummer, and if you need more than 5-6 watts for recording or practice at home just play a normal amp. There are so many good 15-20 watt PP amps out there why bother with 10-12 watts single ended? Build an 18 watter or a deluxe and be done with it. My2c of course, this post is a combination of my opinion and my new meds I'm on, so forgive me till I stabilize if my delivery is a little "flat". The only reason I would do parallel output sockets would be to have a choice between 7-pin and octal.
Class A has it's place but see what 6 watts will do before making things more complicated or try and make an amp be some other type of amp. Triodes have their place too and can be really nice, I heard a bass/warr player playing a workshop with PP 806's sounded real nice (would have sounded even better with bigger more efficient speaker cabinets).
ER wrote:For single ended you need a gapped transformer made for single ended use, you can't use a PP tranny unless it's way oversized or you're in danger of core saturation.
Thanks a lot for your advice!
Dumb question: might core saturation damage the output tranny if one tube of a 2x 6L6 PP is pulled?
FUCHSAUDIO wrote:I would think no damage Marcus. Other than the tube mismatch (which would be harder on the tube than on the iron), I don't see it as an issue.
Thanks a lot!
So you think I can risk the experiment to pull one tube of a 2x 6L6 PP power amp?
Sorry, you mean the impedance mismatch if one tube is pulled? Could this be compensated with the impedance switch?
