Traynor YBA1: best 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!

[Bruce / Mission Amps]

That amp is not really known for early breakup!!
As a matter of fact it is a little closer to cleanish running VOX AC50 with their huge transformers or a JTM45.
Is the amp dead stock?
Still have the 4m volume pots?
Is the cathode of the first triode of the second 12AX7 bypassed? etc.
There are a number of minor mods you can do to smooth it out and increase preamp gain a wee bit.

[mickrhodes]

Yes, it's stock

Thanks Bruce,
Yeah, it's stock. Thanks for the suggestions. I might have to take it to Bob Dixon and get him to mod it a bit. Before that happens though, I was hoping for a suggestion or two on preamp tubes ... I've got Rogers 12ax7s in V1 and V2, and I stuck a Telefunken in V3. Haven't fired it up yet though to see how that Telefunken will affect it. I have to wait 'til my kids are off at school as this thing is LOUD! Anyway, I thought perhaps the Telefunkens would be less strident than the Rogers. I also have some Mullards I could pop in there, but I'm thinking they'll make it more of a clean machine. What say you?
Mick Rhodes

[HTH]

I don't think the preamp valves will make much difference in terms of breakup - you'll get much better results by modding the preamp (imo).

[Bruce / Mission Amps]

Well it probably needs some preamp modding... different preamp tubes aren't going to make much difference there.
The amps are very clean and the trannys are large which really makes them quite Hi-Fi when the power tube are idling midway.
Great amps stock with a decent pedal and fairly easy to tweak.

[mickrhodes]

Thanks ... problem solved.

I used the head for a show last night with a set of NOS Mullard power tubes and a Telefunken ecc83 in V3 and it sounded great. I don't think I'll be popping the hood after all. Thanks for all the suggestions ...