best Traynor YBA1 preamp tubes for early breakup?

[mickrhodes]

I'm playing my late '60s YBA1 through a late '80s Marshall 4x12 with, unfortunately, 75-watt Celestions. It sounds good when it's dimed, but sounds just okay otherwise. I've got a whole bunch of 12ax7s that I could put into the preamp slots. What I'm looking for is an earlier breakup (I know, I know, change the speakers!). Anybody have any reccomendations for me? THANKS!

[loudthud]

Is the cabinet wired for 16 ohms ? You might try wiring it for 4 ohms. As for the 12AX7's, try 'em all. Those old YBA1's are all over the place as to the exact configuration on the first stage. Some have unbypassed cathodes, 4 meg volume pots, and other variations. Many of the one's I've seen don't match the internal schematic exactly. A popular mod is to disconnect the mixer resistor from the bass channel for a little more gain. Lots of possibilities with a soldering iron.

[mickrhodes]

thanks Loudthud

Yes, it's wired 16 ohms. I've had some good results with a Telefunken ECC83 in V3 since I last posted. Thanks for the suggestions!

[Regis]

The YBA-1 has an 8 ohm OT, dunno how that would affect its breakup into a 16 ohm cab. I get plenty of breakup with my two YBA-1A's, try jumpering the two channels together with a patch cord. If you like it you can internally jump them so all you have to do is dial in the two channels like on a mixer.

[mickrhodes]

thanks

I swapped the JJ power tubes for a pair of NOS Mullards, stuck a Telefunken ecc83 in V3 and it sounds great now. I did jumper channels as well, though both my volume knobs are somewhat interactive even without jumpering ... hmmm ... anyway, it sounds killer and thanks for the suggestions.