2 el84s and 2 6v6s PP, same output tranny ?

[Manic]

Im lookin to used 2 el84s and 2 6v6s in the same amp. I know they both have about the same load requirement in PP. 8k. The Blue Angel used 4 el84s and 2 6v6s. Can someone enlighten Me on this please. Sorry if this has already been covered somewhere in this forum. I looked to no avail.

Thnx alot C. Smith

[stokes]

I built an amp with 1 el84 and one 6V6 in SE configuration,and it sounds great,I dont see why it wouldnt work in PP.I would suggest you have one of each tube on each side,not having 2 6V6's on one side of the OT and 2 EL84's on the other.It will take some tweaking to bias them together.I used cathode bias and had to use two different values.You will likely have to have one value for the EL84 and a different for the 6V6.

[Manic]

Thnx Stokes. Yeah from what I gather a wide mismatched output can get hot and lead to premature tube failure even with the same power tubes.

Basically Im lookin to do a top boost pre and EF86 pre into a 30ish what output.
For Me anyway, an all EL84 output doesnt quit get it done.

C. Smith

[6267]

Have you considered trying 6ch6? I believe it's a B9A version of the 6v6.

[Manic]

Thnx for the suggestion. I was wanting to keep the tube selection as "mainstream" as possible. I cant find a data sheet that gives the typical operation using 6ch6 in PP yet. I guess I can compare them running single ended.

[6267]

oops...too many B9A pentodes. 6bw6 *is* identical to a 6v6, same circuits different pins. Not mainstream, but you could probably buy quite a few more of whatever famous NOS brand you liked than with 6v6s!

[drewl]

some of the new bad cat amps do this, plus they run ALL the tubes in parallel so there's like a dozen tubes in some of these things.

[kg]

one thing to keep in mind is that the 84s will have much less input headroom, and may clip (or cause input blocking distortion if cap coupled) way before the 6v6s (or similar).

you might like it, or you might not.

[6267]

you *could* bias them and use resistive attenuation on the input that they both had similar headroom. i.e., if the 6v6 takes -12v bias, and the el84 -8, you can attenuate the signal to the lower-bias tube's grid such that a +11.5v input at the 6v6 grid is somewhere around +7.5v at the el84's grid...?

[Manic]

I have gotten a el84 and 6v6 to run SE with good success. As Stokes suggested I used seperate cathode resistors, running about 300 B+ into a 125 DSE. I'm sure I'm pushing the 70ma limit of the Hammond, but it seems to be hanging in there and Sounds kool.

I may still attempt a PP setup.

Thnx for the info! C. Smith