Matchless Chieftan stock bias EL34s at 133% idle dissipation???

[alexradium]

Just found this Sampson interview,for the record...

That said, there’s a positive aspect to the heat generated by Class A amps.

“Those EL84 tubes lose power when they’re not real hot. An AC-30 will typically get a bit louder as the night goes on. Same with a Matchless. We tried a fan on some of the early amps, but it didn’t work very well. In fact, the amps lost power. It got down to about 25 watts by the end of the night. The amps without fans went up to 40 or 42 watts of clean power. We’ve been railed on by a number of our competitors about this issue, and it’s not an accident that we let the our amps run hot.

“I did a lot of homework on this issue, testing different brands of tubes with various rectifiers, plate voltages, different cabinet settings (head or combo). And every time it produced the same results. I came to the conclusion the cathode in the tube has to run at a certain temperature, and lacking the extremely expensive instrument to measure the temperature of the cathode, I accepted the fact that, because it was cooling too efficiently, it was cooling off the cathode and producing an electronic emission inside the tube and affecting the tube’s performance.”

[Leo_Gnardo]

I accepted the fact that, because it was cooling too efficiently, it was cooling off the cathode and producing an electronic emission inside the tube and affecting the tube’s performance.”

Hmmm, letsee, "cooling the cathode produces an electronic emission." The only FACT is he's full of baloney. A hotter cathode supplies more available electrons, no problem there. But a cooler one producing "electronic emissions" (whatever that means), pull my other leg it has bells on it.

Back to the "sounded great just before it blew up" story. Because of excessive bias current? Sure, I can accept that. But it's not a good way to run your gear unless you "accept the fact" that you're gonna be replacing tubes often, and besides your amp might quit in the middle of a concert or recording session. If that's OK with the person using/owning the amp, well what can I say? Go for it? Better bring a spare. And don't be surprised if you get fewer call backs as a studio guitarist after a couple breakdowns during sessions. Holding up the works because your gear is funky does not impress producers.

While we're on urban legends, what I heard about Matchless early business demise was the boss man was spending company profits buying sports cars and other expensive boy toys instead of supporting the company, until it brought on business failure. If that's the case, I see a certain frame of mind: "Pedal to the metal, and to hell with caution." Yeh, because that always works... don't it?

[Chuck H]

While Sampson may have been confused about what the cathode was doing, maybe he was genuine about his observation of the differences in performance under different thermal conditions for the tubes.?. If so, then why? I can't imagine the cathode temperature, what with being heated by a red hot filament climbing up it's @$$ and all, really changes all that much with internal amplifier temperature. But the rest of the tube innards might. That is, maybe something about the internal temperature of the other elements and the overall environment in a tube could be affecting emission clouds, electron transfer efficiency, gaseous impurity collection, etc.?. I, for one, don't plan on testing any theories on and writing a tube cook book. Not as long as I'm getting happy results running my tubes in the safe zone anyway. But I'll concede to not disregard that something may be real about the phenomenon because IME those Matchless amps do sound loud and awesome.

[Leo_Gnardo]

those Matchless amps do sound loud and awesome.

If you build amps along the Vox design, plus play through hi efficiency sensitive speakers, I bet they'll sound loud and awesome too. Maybe even "immediate." And I bet they'll do that even if you stay inside reasonable safety margins.

Even though I haven't heard your creations Chuck, I expect it's likely you're already there. As if I have to tell you.

[Chuck H]

Even though I haven't heard your creations Chuck, I expect it's likely you're already there. As if I have to tell you.

Close Of course it's an ongoing effort. As it should be I think. So what worked great yesterday needs improving today

[g1]

I'll agree with Chuck that Sampson may have been reporting some observed phenomenon. But surely it won't have been the tubes? All that stuff should be on the data sheets, and a tube that needs more heat than the heater can supply would flop.
This would be very easily repeatable and seeing as he threw the Vox name in there, I'm sure it would be common knowledge if true. Has anyone ever heard of Vox's getting louder the longer they are on?

[Chuck H]

Has anyone ever heard of Vox's getting louder the longer they are on?

Nope. But I sometimes hear other things I was unfamiliar with only to learn it's a known thing. So I try to stay open minded.