Class A amplifiers

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

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

Give it a lift up to be even better than your hearing now, replace all the power supply caps and any other electrolytics on the boards they will all defiantly without a doubt need doing by now.

Cheers George

Same
The only cost a good Class-A amp does is raise your power bill and room temp if left on for no reason, a large biased class-A actually runs cooler when played hard.
A Class-A amp is the best BUT!!! it has to handle everything that that high Class-A bias is sucking out of it and it’s power supply, if all is designed correct nothing but nothing touches it. (in the distant past, I made huge "water cooled" two man lift ones that were 150w based on 20w 1970’s Nelson Pass bi-polar class-A, that today still have never been bettered)
https://www.passdiy.com/project/amplifiers/construct-a-class-a-amplifier

Cheers George