Valves for 1977 Traynor YBA 1

bloo

Hello

I have a 1977 YBA-1 bass master - (that i play bass through not guitar)

Im looking for replacement valves to give me more bass, punch and tone..hopefully just a fuller sound than i have in there. It takes two 6ca7's (el34's) and three 12ax7a's. There is a mullard el34 and a pinnacle el34, a GT 12ax7a and 2 others that i cant make out in there already.

Can anyone recommend a decent set of valves for it? Ive my eye on some JJ e34l's and a set of jj 12ax7a but there are quite a few options out there, are they really going to make that much difference? Also from what ive read i wont need to bias my amp... is that right?

If anyone has any ideas that would be much appreciated

Thanks!

Eoin Madsen

The different brands do have some distinct differences in sound. It's hard too judge in a given amp without trying a few different types.

You have to get a matched pair of EL34s (the mismatch in it presently is pretty odd and probably not good for the amp, unless they were installed by someone with some serious valve matching equipment). I wasn't hugely gone on the JJ E34Ls I tried (especially for my bass; I didn't think they had a particularly clear bottom), but they are a good quality valve so not a bad place to start if you're not sure what it is you're looking for yet. I'd buy six or seven different ECC83/12AX7s if I was you - these ones can be mixed around to taste so it's worth trying a few different ones.

I did a quick google search of the amp and from what I can gather it has no variable bias adjustment when stock. Adding a bias pot seems to be a common mod, and you might want to look into this (or see if it's already been done). It's not so much a question of not needing a bias adjustment, just that it's hard to do it. I presume the preset bias is somewhere on the cold side of average, so that the amp functions with most EL34s. But, optimally, any amp should have a bias adjustment made for any pair of grid-biased pentodes.

Paolo_M

For more bass you could try out a set of KT77s.
Make sure to re bias as they do bias a little hotter than EL34s. Other than that they are a direct replacement, same heater current draw, plate dissipation, pin assignment etc.etc.etc.
They'll give you a good bit more low end, I put a set in my JCM 800 and haven't looked back.

I would guess it's a fixed bias amp as I cant imagine you'd get 50W output from two EL34s with cathode biasing.

****** Just checked the schematic and it is fixed bias but there is no bias adjustment pot in the original amp. Hey a true fixed bias amp for once!!
Anyways without the adjustment pot you wont be able to bias correctly for KT77s so I wouldn't recommend it.

PS: You might be interested in checking this out:
http://www.kilback.net/Traynor_Tweaks_rev12_sk2007.pdf

spoonbadger

Another type to consider is the KT66s. They were the valves used in the original marshalls, like the JTMs and bluesbreaker. Brilliant bass response, very clear and full sounding, not as compressed as EL34s.

Btw,you should get your amp converted to a variable bias. If you're good with electronics,you could try it using the instructions in Paolo's link (If your not, dont attempt it. Dangerous stuff inside tube amps!!). Otherwise you could just it bring to an amp tech,they wouldnt charge too much for it.