5881, 6V6, EL84, or 7591 for triode-strapped operation?

[Shea]

Hi, I'm a new member and a newbie to tube audio. I've been building, fixing and modding guitar amps for about 10 years, but most of us guitarists take a far cruder approach to tube circuitry than y'all do.

I'm thinking of building a tube-driven iPod dock with SET output stages, just as a starter project. I'm going to stick with inexpensive and readily-available tubes and transformers. I'd like to use tubes with 6-volt filaments and indirectly-heated cathodes for simplicity's sake, which I think will limit me to triode-strapped pentodes or beam-forming tetrodes. Maybe I'll put a triode-ultralinear-pentode switch on the back of the chassis just for fun.

I'd also like to stick with tubes that are no taller, or at least not much taller, than an iPod classic.

So, as far as I know, the prime candidates are 5881, 7591, EL84, and 6V6. I'll probably use a 5Y3 or GZ34 for a rectifier and make a 5-volt regulated DC supply for the iPod using one of the heater windings on the PT.

I'd appreciate any comments or recommendations regarding using any of these tubes triode-strapped. Also, if there is already a proven DIY design for a SET output stage using one of these tubes and an inexpensive output transformer, I'd appreciate if anyone could point me toward it.

[Miles Prower]

Originally Posted by Shea

I'm thinking of building a tube-driven iPod dock with SET output stages, just as a starter project. I'm going to stick with inexpensive and readily-available tubes and transformers. I'd like to use tubes with 6-volt filaments and indirectly-heated cathodes for simplicity's sake, which I think will limit me to triode-strapped pentodes or beam-forming tetrodes. Maybe I'll put a triode-ultralinear-pentode switch on the back of the chassis just for fun.

6AQ5s (7 pin mini version of 6V6) make nice pseudotriodes, if you don't require very much power because you're not gonna get very much from any SET unless you go for something like a 845 or trioded 813 and the bigvolts they'll require.

[Wavebourn]

6AQ5, 6V6, 12L6GT, 6П1П, all are nice triodes. Also, I like very much 6П15П as triodes.

[tikiroo]

I have 7591's running in triode mode (for hifi not guitar), getting about 8-9W in push pull class A with 400V supply so single ended should get about 4W I guess. JJ has triode curves for the 7591 on their website.

[rotaspec]

I agree with Wavebourn on the 6P1P. Very nice as triode or pentode SE (haven't tried UL yet). 6P1P-EV take a looooong time to break in and sound their best.
My computer amp is a 6N1P-EV driving two 6P1P-EV in pentode SE and it produces a very clean 3W or so with OPTs pulled from a ECL82 tubed console (original console had 3.5 ohm speakers, but I am running 8 ohms so the impedance the the 6P1P sees must be up around 9-10k) .

[Eli Duttman]

As long as 2 WPC is sufficient, any member of the 6V6 clan will do very nicely. Tubes in the clan include: 6V6, 7C5, 6005, and 6AQ5.

BTW, a 5965 would be an excellent choice as the voltage amplifier.

[Shea]

Thanks everyone!