EL34 or 6L6g

[H713]

The input stage/driver was another pentode - a 6SJ7 - using a simple un-bypassed 1.5K cathode resistor if I remember well. So I just connected something like 100-120K resistor to the 6V6 plate put some 10 uF cap in series and connected the other end of the cap to the 6SJ7 cathode. I didn't measure anything because I didn't (or better he didn't ) have the tools on his bench. Just trial and test until it worked (sounded) satisfactorily.

I'll keep this feedback technique in mind... mind you the amp I have in question is a 6L6GC push-pull amp, but it's got the same issues: less-than-spectacular output transformers (Edcor), crappy assembly (I really screwed up the grounding scheme), and lots of noise. I tucked the thing away on the "deal with later" shelf, and I've been thinking about how to improve the damping factor without making it unstable... Of course, I have to deal with the grounding first.

 

[Bill poster]

Anyone mentioned the 7581A yet? A Turbocharged 6L6

 

[larryldspkr]

I have a single ended KT88 amp, it's switchable between triode (5 watts) and pentode (15 watts). Best of both worlds.

Larry

 

[anatech]

Hi Bill,
I've used them often enough. Nice tube, same plate characteristics as a 6L6GC with higher dissipation. I use them whenever I have an amplifier that likes to eat the new 6L6GC tubes, like a Fender Twin for example. They last longer in addition to standing up to the higher plate voltages.

New tubes that are interesting are the ones sold by New Sensor. The 6L6EH has the same plate dimensions as a 7581A and they put up with high voltages. So these days I just use the 6L6EH and life is wonderful. Otherwise the easiest 7581A to get would be the US military ones sold as NOS types. I see the prices on these have gone out of sight since people figured out what they are. 🙁

So yes, a 7581A is about the nicest tube in the 6L6 family as far as I'm concerned.

-Chris