Traynor YBA-2 eats EL84 for lunch B+ too high?

[g1]

Maybe way out of left field but is the OT stock?
What tubes are you using now?

[km6xz]

I agree with Gtr, the tubes are not even 6BQ5's, even the NOS claimed GE's, they are tubes that has similar characteristics designed and built in Eastern Europe or Asia for domestic markets, usually with a different base. The tubes might be fine, just different so have different mu. You yourself see that they bias better when cooled with -20, why not increase that so the tube is running as it was intended? So what if it takes -26 to see cross over notch start up, these tubes need it, the only lower B+ used when the amp was new, fitted with different tube with different characteristics required different operating points. Until you get a handle on what is happening, don't change any more parts unless you can prove they are defective. That introduces more variables to a situation that you are already confused about. After the main problem is resolved, establishing a suitable operating point, rebuild the amp if you want.
This is not rocket science, it is a very simple amp and using well established technology, don't make it more complicated by introducing new variables. Forget the specs, the schematic values only corresponded to the typical amp in its day, coming off the assembly line running on 110V mains using tubes that have not been available for a long time regardless of what boxes they came in say. If you do many amps, you should build a clean wide range variable C and B supply for setting unknown tubes.

[Chuck H]

Most of the custom builders, well the "better" one's anyways, would recommend running the plates of an EL-84 at +300 volts... Bottom lime ; you need to drop abouts a 100 volts....

-g

Well, Gary, I'm not inclined to reveal my client but he's a pretty big cootie. I designed an EL84 amp for him with 355V to 360V on the plates and most players seem to like it very much. In my experience EL84's (curent production anyhow) start to lose the EL84/Voxy magic chimey-ness past about 330Vp. But at 400Vp they can deliver exceptional power and bottom end for their size (though more flat and sterile sounding). All points in between are a compromise between these two strong suits. Honestly, forget the buzzy mess of "18 watt" amps out there. It is eminently possible to design a good sounding and appropriately powered amp with a pair of these tubes. But you can't do it at 300Vp. My design, with 360Vp, only puts out about seventeen clean watts. In bench tests it averages twenty to twenty five dirty watts. With an efficient speaker this is doing well in clubs. A speaker driven line out has been accommodating for bigger venues. In the low 300's you would certainly need to run four tubes to make a gigging amp.