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Class A Power Amp Degredation

Dear Forum Members,

I've read in several places that because class A amplifiers run hard all the time and most people don't cut them off, they wear our faster. Plus, because they remain on all the time they burn much more electricity and generate lots of heat, some more than others, at least that's what I'm told. I wonder what happens if I have to go away for a day or two?

I can't afford to purchase a brand new class A amp so I wonder if I should even consider the purchase of a used Mark Levinson, Pass Labs or other class A amp? The only amplifier I know of that can be switched between class A and A/B is the Plnius. I am told that this amp only run very hot when it's running in class A.

Here are my questions:

1. What should I look for in a used amplifier?
2. Do class A amps wear out faster than other amps?
3. Are there amplifiers that can match the musicality, sound staging, bass and sweet sounds of a class A amp? In other words are there any class A/B amps that have all of the quailities of the class A amps?
4. If I do decide to buy a class A amp how far back in years should I venture? Right now I am considering the Mark Levinson 27 or 27.5 or Pass Labs X150/250 and X150.5 and X250.5 amplifiers. It's been suggested that the Mark Levinson is more musical????? I just want to get the best amplifier to run my audio system.

I will be driving Magnapan 1.6 speakers which does require a fair amount of amps/power to drive them. Also I mostly listen to classical music, large/small scale choral works, contemporary and gospel music and all modern jazz. I love the human voice. I also love a huge sound stage with lots of depth perspective.

Any assistance and suggestions you can provide will be very welcomed. Thank you so much for taking of your time to respond to this plea for help.
rbwinterlink
yioryos's avatar
yioryos
723 posts
 
Rbwinterlink
The ML 27 or 27.5 are not class A. For class A Levinsons,look for the ML 20.5 or 20.6 monoblocks.I own the ML 27.5 and it runs A,A/B class BUT it is a very very nice sounding amp.Never owned a Pass Labs amp,so I can't offer a comment for those.
Regards
George
ngjockey
1,042 posts
 
Never heard anything more than guesswork and BS about class A being less durable. I run in class A for 8 months straight every year. Keeps the gas bills lower. The only SS amp I've ever had to replace output devices on was a 15 year old A/B amp which had 4 overdriven MOSFets per channel for 100W. It could get pretty hot driving 2 ohm Kappas over 100dB.
atmasphere's avatar
atmasphere
12,168 posts
 
Its easy enough to find a tube amp that is class A and 30 watts. Most speakers of such efficiency are designed for amplifiers that have a high output impedance (one of the few exceptions is the Avantgarde Trio which is intended for transistor amplifiers only). This is because high efficiency speakers also have high back EMF- and this really messes with amplifiers that employ loop negative feedback.

for more info see http://www.atma-sphere.com/papers/paradigm_paper2.html

So for such a speaker I would strongly advise a tube class A amplifier; about the only transistor stuff that is suitable for such a speaker is the Pass Labs First Watt amps.
rbwinterlink OP
72 posts
 
My dear friends, thank you for each and every comment. While I understand that a great majority of power amps are not fully Class A only, I still wonder. Would not the Class A/AB power amps like the Mark Levinson 27/27.5 run hot due to the fact they are operating in Class A most of the time depending on the listening level?

In my case I would not ask the power amp to drive my Maggies (1.6) at loud levels. At this rate would not the power amp be operating in Class A from idle to most of my listening levels? Just wondering.

I am leaning towards the Mark Levinson 27 first and the Pass Labs X150 second. Tell me all, what is the difference between the Mark Levinson 27 and 27.5 in terms of musicallity? As stated in my initial post I love the human voice and listen to lots of classical choral works, big band and small group jazz. And I am looking for the amp to produce a wide and deep sound stage with an accurate presentation. I am thinking each of the two amps mentioned here can do that for me. I look forward to your response.
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