Care & Feeding of Traynor Bass Master YBA-1A Mark II amp?

[Rhodesplyr]

A friend of mine has been using a Traynor Bass Master YBA-1A Mark II for gigs as a keyboard amp (borrowed from someone else). I didn't know much about it--or Traynor amps in general. It's missing its name badge on front, so I had to find the model information on the back. He was under the impression that it was a ~40 Watt amp. I was curious because I helped him carry it, felt how heavy it was, and saw the cooling fan inside.

I was surprised to read that Traynor rated this amp 90 Watts continuous and 150W peak. From a pair of 6CA7s? Hunting down the schematic, I see that it runs the plates at ~540V, probably more, depending on mains voltages.

It seems to work fine at present, but I was wondering, if it were to need new output tubes, what current production 6CA7s/EL34s best tolerate these plate voltages? (Yes, I know that these tubes are rated for 800V, but you don't see that tested very often.) How quickly do these go through output tubes?

Also, to get 90W from a pair of 6CA7s, I'm guessing that it runs in Class AB2 or even Class B. Correct?

[Rhodesplyr]

Since posting, I read that Class AB2 and Class B amps need to be transformer coupled, so scratch that...

[Chuck H]

The Traynor power claims are absolutely false. Though there are some here that will argue it. It's basically a high Vp and a cool bias with a bit of extra drive voltage. It'll do more clean watts than average, but 90 simply cannot be accurate for sustained output.

In a perfect world the 6ca7 tube would be putting out about twice it's dissapation for half a cycle. And therefore 90 watts should be possible. But it's not a perfect world. That AND in order to achieve the highest possible clean output the amp would sound lousy overdriven due to excessive crossover distortion. One reason why they are almost never set up that way.

Great amps though. I still have one I use as a test platform for ideas. It sounded great stock and sounds good almost no matter what bizzare circuit I stick into it. Probably not the best test platform for that reason. Everything sounds good through it.

[Gtr_tech]

Hmm....back in the late 60s and into the 70s Traynor didn't publish output power specs in company literature. But its still common sense here.....a pair of output tubes will achieve a nominal output power at a given plate supply and bias arrangement as indicated in the tube's datasheet.

[Rhodesplyr]

The Traynor power claims are absolutely false. Though there are some here that will argue it. It's basically a high Vp and a cool bias with a bit of extra drive voltage. It'll do more clean watts than average, but 90 simply cannot be accurate for sustained output.

Thanks for the reality check. The EL34 datasheets I can find show 70W as about the most you can obtain from a pair in AB1 operation, given the output transformer. There is a listing for 100W, but that requires an 11k OPT primary. But, as you say, that would require cool bias and crossover distortion. As someone once remarked to me in a discussion of another amp regarding maximum output power, "You might get that output at a narrow bandwidth, and it would sound awful." The EICO HF-60 claims 60W from a pair of EL34s, but most people think that the HF-35 sounds better.

The YBA-1A seems to me like an 6CA7-based amp on its way to being a 6550A/KT88 amp. Perhaps they stuck with 6CA7s for cost reasons.

Otherwise, as you say, it seems to be a nice-sounding amp. It's one of the few I've seen where you really have to delve into the manual and the schematic to find out what the difference is between the two input channels. Channel Two appears to be what might be called a "Bright" channel on another amp.

[g1]

It's possible that 90Watt spec. is a typo, the YBA-3 was rated 130W with 4 6CA7, so I would expect about half that with 2 6CA7's. The original YBA-1 used a pair of 7027's and was rated at 45W. They changed to 6CA7 around 1967. Not sure when the big bottle 6CA7 was introduced or why Traynor switched to them but he stuck with them in the higher power amps except for the oddball super custom special with 6KG6's.
Most of their amps put out more power than other amps with the same power tube complements, but that 90W spec. seems way out of whack.

[Rhodesplyr]

It's possible that 90Watt spec. is a typo

You could be right except that Traynor also claimed 150W peak power output. Thus, I don't think that the 90W figure was a typo. Audio electronics history is rife with companies making inflated claims about output power to try to sway buyers.

For example, the famous Dynaco Stereo 70 is a great amp (if modified), but with the stock power transformer, it can't produce 35W from both channels at the same time.