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.
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1-If you are going away, definitely shut off the system. It may take an hour or two to get back up to where you will like it when getting home.

2-Having owned many class A amps, I'd state very confidently that they don't wear out faster as long as they are well ventilated. They do run very hot but are designed for that. The problem is that when a class A amp blows, it usually goes badly. Look at how many 20 year old class A amps are out there working perfectly...

3-The old standby on on Class A amps that is switchable from A to A/B is the Yamaha M series. If you are looking to just play, these are great. The M45 has around 150 wpc and the M60 through M85 have way more power.

Finally, I can't put Levinson and Pass in the same ballpark. The sound is drastically different. I love Pass and can't stand Levenson's "dryness" in comparison.

Keep in mind that most Class A amps are only in the A mode for the first 10-15 watts and then automatically switch to A/B. So loud listening will be in A/B anyway. Some amps are always in class A but those are usually rated in the same league as tube amps (20-60 watts). Don't be fooled by an amps rating of high power and class A, it's usually an either/or situation.
the theory that class a outperforms a/b and is debatable. buy the amp that will best serve your speakers, regardless of catagory.
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.
The first thing that cuts the life of an electronic circit is running the individual compents beyond their rated range, and the second is heat. Then again, a class A amp with adequite heat sinks and good ventilation can run cooler than a class A/AB amp with less adequite heat sinking.

Interestingly, none of the amps that you mention are class A amps, all are class A/AB, so more research is in order on your part.

In the end, you are buying sound quality, not circuit topology, so this should be your primary criteria.
Rbwinterlink, in general it is best to turn off your system if you leave home for a few days regardless of the class of operation of your amp. . . besides power consumption concerns for all class A amps and many class A/B amps, there is the issue of inclement weather which can cause power outages, spikes, and worse.

Pure class A amps are -- as far as I know -- always furnaces. . . . as they draw current at the same peak value regardless of what they are doing. . . whatever is not used for making music goes up in heat.

Things become more murky with class A/B devices. Some are veritable furnaces like the Pass X.5 series and my old Rowland 7M monoblocks. . . others run as cool as cucumbers like the Theta Citadel monos -- one of the sweetest amps I have ever heard.

Then there are switching amps -- mostly class D -- that most often run very cool to the touch and have operating efficiency ranging from 85% to 98% depending on manufacturers and models. In most cases these amps have output properties (high damping factor of 500 to 1000) that make them particularly suitable for driving low impedance speakers like Magnepan 3.6. I listen almost exclusively to classical music and my amp is a class D Rowland 312, which runs cool even in the sweltering summers of Austin. . . I couldn't be happier about its sweetness and its power to deliver staging, imaging, detail, and nuance.

Besides power draw from all class A and some class A/B amps, I would not be terribly concerned about the inherent musicality of any class of operation. You will find musically satisfying amplifiers in class A, A/B, and D alike, and at least as many that will put your teeth on edge -- no matter what their class may be.

regarding Pass Labs amps: given that I have 101dB speakers, am I correct in my thinking that their very pricey (but extraordinary from what I've read) Xa series would sound the same as their other models in the class A mode? At 101db, I can go to serious dbl levels in the 15 watt range, but would love to have that extra wpc, for those rarely needed ear bleed, moving picture frame levels, given that my speakers can handle 300 watts. Anyone?

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.
I am currently driving my Definitions with 35 glorious Bel Canto SET wpc with NOS tubes, and am very happy, indeed. Every now and then, though, I would love to know [even though my 35 SET wpc get me some serious dbs] what 122db sounds like with some particular music I love to listen to. Original question? thanks again.
If you do plan on buying a used amp that is around 15 years old, I'd replace the capacitors. Other than that, most SS amps (like the Levinsons, Krells, Pass Labs, etc.) are built conservatively such that they should last decades without fault.
Edwyun is correct, in that my Rowland 7Ms came out of the factory in the late '80s and are still going strong after 2 decades. . . except for the monthly power bill.
Warren, you don't want to experience 122db. It hurts. I had Cornwalls, 102db/1watt, running from a Threshold 400A and a Yamaha M-80. I never made it past 1/2 volume. This could get well over 128db if you do the math. If 110db is THX, 112db is Ultra THX, what is 128db, nuclear THX or New Years fireworks?
Personally, I liked running my 20 watt SET better.
Elevick, I'm with you. SET is addictive. But there are those times. I think 35 wpc driving my 101dBs translates to 116dB. Just shy of ear bleed level. Good enough, but there is music that 116dB is just the begining. Not worth the switch however, but was curious. Anyway, nobody answered my question.
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.
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.
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

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.
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.