Yay Traynory YBA1-1A Bassmaster Mark II. What a long name.
Not that familiar with the Traynor amps but this one seems somewhat special because it is powerful for an amp that has only two power tubes. People on the net say anywhere from 65-100W but I remember this one starting to clip around 76W or so.
Kind of a funny image since there are five different brands of electrolytics in this amp. Lots of people have had their hands in this over the years, Oh well. At least it works good and there are no more caps from the late 60s/early 70s still in use. This one has to be reliable, it is a studio amp at Bricktop Recording.
And yay again you can pop off the top for easy servicing. The amp is basically layed out like a Fender with the eyelet board so it is easy to trace the circuit and work on.
So yes YBA-1A has more clean headroom and power than the YBA-1, and larger transformers. I think the YBA-1 used 7027s and was rated for 45W and the YBA1-1A used 6CA7s and was rated for a probably false 90W rating. I am kind of speculating so please correct me if I am wrong.
Like a lot of the old amps it has two channels with a high and low input which can be jumpered together, blending the two channels.
Traynor output doing about 70V pk-pk into 8 ohms for 76W at clipping.
Traynor YBA1-1A MKII schematic
Also notice the schematic lists 8 ohms as the OT load. Lots of ‘net stuff says you can run these at 4 ohms but in my experience the current draw runs off too much, exceeding 200mA, and it will probably destroy the tubes. I wouldn’t continue with that. At 8 ohms no problem. Perhaps this impedance confusion is just due to YBA-1 vs YBA-1A mixup.