Class A amplifiers

emrofsemanon:
I’ve recently come a long way on my push-pull, class A, SS, tube, hybrid, SET, SIT amplifier journey.  IMHO, my SET implementation (dual Coincident 845 Turbo’s -28 watt and 94db efficient speakers) brought me closer to acoustic music than any other implementation (of approximately 25 different amp combinations- Bedini, BEL, Threshold, Muse, ARC, Moscode, Counterpoint, etc.). Terms like organic and realistic applied.  The realism of an acoustic guitar was breathtaking. However, the tradeoff was weaker dynamics- somewhat thin sounding on large dynamic swings of rock and orchestral music.  In the end, I settled on an Firstwatt SIT-3.  Nearly as good as the Coincident SET in realism, but with a far superior coherent presentation of the entire audio spectrum. I can say I’m temporarily satisfied.

The OP is asking about Levinson gear.  At least the classic era Levinsons, some of them do cook themselves to death. I have a No.23 and the repair job is going to be near $3000.  The authorized repair center explained that the Levinsons do tend to do that. 

While they are "high bias" Class-A Plinius 102 amps cannot be biased "Pure Class-A to their rated 8ohm wattage output". They run A/B.
To have those heatsinks at a constant safe 55-to 60c they would have to be approximately 4 x that size for the amp to be safe to be pure class-A all the way.
Search all you like and won’t find it stated anywhere they are Biased up Pure Class-A all the way into 8ohms, not even on their archived website.
https://web.archive.org/web/20060115165723/http://www.pliniusaudio.com/pro/pro02.htm

At a guess I would say 50watts of Class-A and the rest is B up to 125w

Cheers George

I think this should vary greatly based on thermal design and usage. No reason why a Class A amp of any rating can't be designed with enough ventilation and heat sinks to last a lot longer than that.

Is Your particular Class A amp going to last 10 years before servicing? I have no idea. :)

No reason why a Class A amp of any rating can’t be designed with
enough ventilation and heat sinks to last a lot longer than that.

Obviously no experience building >100w Pure Class-A biased amps.


This is why the Plinius 102 is no way 125w Pure Class-A bias, and is not stated anywhere that it is but from those mimicking the sales person/s sales pitch
THERMAL RUNAWAY BECOMES A REAL PROBLEM at Class-A 100w with B to 150w when combined with ambient temps. Also internal component temps are massive and life greatly shortened

ME did the correct way here using speed controlled chimney heat sinks, with their 60kg monster.
https://ibb.co/TbQShYK
https://ibb.co/WzQGpMb

And so did Krell with their real Class-A’s like the KSA-100 and 50 https://ibb.co/zQ8vJF6
Instead of using pseudo class-A plateau/sliding bias in their later models

I went a different way, 3 x bigger than the ME-15500’s but using liquid cooling for the 6 x 100w Pure Class-A, I built over 10 years, using pump/radiator/fan combo transistor heat jacket, but after 15 years use corrosion of some parts became a problem.

Cheers George