Living With A Class A Tube Amp

You most likely have either ultralinear or pentode

pentode being a purer circuit without all the feedback as in a Ultralinear circuit.

I always thought that ultralinear was synonymous with pentode, and that triode was the purer circuit. Was I mistaken?

@atmasphere  ,

quoting from my owner's manual:  "CIRCUIT TYPE:  Push-Pull Ultralinear Amplification in Pure Class A"  then "POWER OUTPUT 50 watts-Triode  100 watts - ultralinear."

As always, I defer to your knowledge on these subjects.  I had just assumed that when I was blasting away at ear bleed levels and the room was getting warmer the output tubes were taking a beating.  I also acknowledge that a lot of my preconceived notions are often wrong.  

I will say that this current set of EL34s is holding up better than the last set, but I am sure that there could be other reasons for that.

@atmasphere  , thank you for the explanation--that is interesting and makes me a better informed hobbyist.  

"Pure Class A" was a direct quote from the owner's manual, so that is all I know about it, as my ability to comprehend electrical theory is limited.

I always thought the room got warmer when I used to crank it way up, but that typed, these days I listen at low to moderate levels, and after a couple of hours, if I put the palm of my hand on one of the transformers, it is hot enough to make me remove it (my hand) fairly quickly.  And, after a few hours of listening at low to moderate levels the room still gets warm.  So I do not know for sure that  making it scream had it running hotter or not--I just felt that it must be; and I also do not know which category of Class A Cary was referring to by "Pure Class A"; until now, I was not aware of the different categories.

If it makes a difference as to how hot it gets, these days I always run it in triode.

no need to bias tubes.

Don’t you still have to adjust the bias on the one output tube per side that you do have? That is, unless it is self biasing?

This is not a class A amp. It is a push pull.

@carlsbad2 Push pull amps can be class A no worries. The Dynaco SCA35 using a pair of EL84s was a class A PP integrated amp. We’ve been making class A triode PP OTLs for decades.

If you were not aware that amps other than SETs can be class A, now you are. The trick is just the same as in an SET- the power tubes do not go into cutoff during any portion of the output waveform right up to full power. So you can also have class A solid state PP amps too.

@atmasphere  , thanks for clarifying that.

@jrcotner  , my old Cary V-12 is switchable between 100 wpc ultralinear and  triode, and in triode Cary says it is 50 wpc class A.  Yes, it does run hot, but I have not had to do anything special with it that I didn't do with my two previous tube amps.  I bought a set of 12 EL34s (reissued Russian Mullards) near the end of 17 and after a bit two years of being pushed pretty hard and a couple of mishaps they were sounding tired and the bias was doing funny things.  Sometime in early '20 I replaced them with a set of the reissued Russiian Tung Sols and they have held up beautifully (however, I don't run them as hard and no mishaps involved).  

As long as it doesn't get way too close to the curtains, I think you will be okay.

@immatthewj FWIW, 'pure class A' is a marketing phrase. As far as engineering goes, a circuit is either class A or its not. None of this 'enriched class A' stuff you often see (such amps are class AB). In your case my guess is class A1.

I thought after I read your postings on the different categories of Class  A that "pure Class A" probably was the manufacturer romanticizing the owner's manual.  Thanks for the info.