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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

Showing 3 responses by atmasphere

atmasphere's avatar
atmasphere
12,109 posts
 
Elevick, a class A amplifier, by definition, is class A at full output. If not, it is called class AB. There is no exception to this definition- the amplifier is class A if the output device does not go into cutoff at full power.

It is true that class A amplifiers last just as long as any other type of amp. They do run hotter- trading efficiency for improved sound quality. Class A operation is the most desirable mode of operation if the best sound quality is your goal. All other classes of operation trade off greater power output (and less heat) for less sound quality. Unfortunately it is not so simple to say that all class A amps sound better than all other amps; that would only be true if that class A amplifier had all the other most desirable design attributes and was properly executed. What is the best of the other design attributes is controversial, but the class of operation is not.
atmasphere's avatar
atmasphere
12,109 posts
 
Hi Warren, The Zu Definition is available in a 30-ohm version. All the reports I have is that this version of the speaker is really something to hear, and it can be easily driven by smaller tube amplifiers, which will sound a lot better driving 30 ohms than they will 3.3 ohms.

If you are set on going solid state, I would consider one of the First Watt amplifiers, rather than something that makes 300 watts. The First Watt amps need more efficient speakers, but they also sound better- and will be very happy with a 30 ohm load, should you decide to go in that direction.
atmasphere's avatar
atmasphere
12,109 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.
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