"
you have to accept that every 3 or 4 years you have to send them in to get serviced"
Bad advice, not true.
Bad advice, not true.
Class A amplifiers
I was watching YouTube reviews on Hifi and one guy said if you like Class A amps you have to accept that every 3 or 4 years you have to send them in to get serviced Becasue the heat inevitably causes issues? Is this true? I have a friend with an older Maek Levinson Class A amp and he was looking to sell,it to me, and am just wondering if Class A amps are like a boat, always costing you more . Anyone?
49 responses Add your response
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 |
I haven't had the personal experience, but when you see old class A Krells for sale, (as one example) the seller will frequently mention that all of the power supply caps have been replaced at factory; and I have read that it's because of the high heat generated over years of constant use. For that reason, I have always avoided buying a used one even though I was tempted when I saw one that hadn't been refurbed. Is there no truth to this? |
Those old Krells are old. Any amp that old needs work like that. I spoke to Krell and they were actually pretty cool. The guy in service dept I spoke to told me what models to look for and which to stay away from. Also told me I’d I sent him the serial number he’d look it up before I bought it to make sure it wasn’t some lemon. I F I go with Maggie’s I want to get one of those old monsters , but more likely I’m going to find a smaller used one , I found a Mark Levinson 50 watt , or I’m getting the Sugden and getting just efficient speakers. |
"i take it to jiffy lube first of every month... they do full lube job and change the air filter... i plan on driving it forever" Right. Excellent advice. 3 months or 300 hours, whichever comes first, I ship my Atlas right back to Mark at Rogue. Great service; they even changed the wiper fluid during the latest trip. |
Class A amps run hot! And it does lower there life expectancy. With that said if you dont mind the heat it gives off (like some of us that live in Texas do) and you dont mind sending it in after a period of years (it will be needed) then go for it! :-) P.S. I have a old ADCOM GFA 555 that is class AB and it still sounds awesome today after 30 years because it runs cool to warm never hot like fry an egg hot that class A amps get. Im not comparing the sound, of course the Krell or Mark Levinson amps do sound better but at a much higher cost. If I were the OP I would ditch the idea for a highly investigated and informed used McIntosh amp and be done with all this "amp runs Hot, Class A, send in for service" talk. Find a special amp that MAC makes, do some research, they do make some great amplifiers (its what they do best) Matt M |
Like most blanket statements, its no true but has some kernel of truth. Class-A amps typically run hot because they dissipate 100% (actually in most cases, 200%) of their rated power all the time. But that is a design condition and ought to be accounted for so that it is irrelevant. Depending on how they are designed, cooled and parts chosen, class-A operation, and its attendant heat generation, can have very little effect - or can be a long term issue. I have hundreds of units that I designed in the field, many approaching 30 or over 30 years old with essentially no failures due to accumulated heat. While these are not pure class-A, they are very high bias amplifiers that dissipate a LOT of power; but they are designed for it. The primary components harmed by heat are electrolytic capacitors. transistors can run very hot with no ill effect, and most resistors can too unless the are directly over-powered (e.g. run at or near their rating or 1/4w, 1/2w or whatever). Film caps too typically are immune unless its so hot they melt -- and that's HOT. I'm sure there are some poorly designed amps out there. Avoid them :-) |
Add my name to the Nelson Pass Fan Club. His amplifiers have a reputation for being highly dependable. I have (and Love) a First Watt Sit-3; It does not generate much heat at all and I expect many years of trouble-free service from it, as that would be consistent with his company's offerings and his design philosophy. Pure, simple and with few 'moving parts'! Happy Trails to you, Bear............. |
completely false statement. Been repairing amps for so long now it comes down more tot the quality of the parts then the heat if the units are vented correctly and they have good heat dispersion. Any old component you purchase probably needs a parts upgrade. Last night we compared three class A amps Coda, Carin and BEL. We were surprised with how well the BEL amp sounded. Very musical sounding amp built in the 90s. Still going strong although I think changing a few caps is a good idea, I also think the Nichicon PS caps will sound better along with Audio Note resistors and capacitors or Amtrans. I have been repairing, modifying and building audio components for close to 30 years now. Don't worry to much as the caps, etc., can be easily changed. |
As others have mentioned, it depends. All Class A run warm. Many run hot. Some run so hot that they dry out the electrolytic capacitors. Solution: don't run them hot, use electrolytic caps only in the power supply, and isolate those caps from the heat sinks. Personally, I run the amplifiers' heat sinks at comfortably warm and the power supply at room temperature in a separate rack in another room. That's a bit extreme - but not as extreme as George! |
That is a giant load of dog doo. I have 4 class A amps in house. Two First Watt amps, and a pair of Monarchy Audio SM70mkII's (I run these as mono blocks) The FW J2 is the newest,built in 2017. I am the second owner of FW F5,that I've had for at least 6 years. Not sure when Mr.Pass built that one. The Monarchy's are at least 10-12 years old. The pair I have I believe are one of the first MKII's that were built. Not a hiccup out of any of these amps. Ever. Ya gotta love YouTube. |
It depends on the design of the amplifier,whether the manufacturer pushes it close to the limit or not, and whether it is provided ample heat sinking or trying to save on an undersized heat sink. My good friend has the legendary Mark levinson class A monoblocks (the ones that weigh a ton). He had them when ML came out with tit, and since then has them CONSTANTLY ON. Yup, never power off, and they are happy campers. With most amp brands I would be worried, but ML class A ere built to last. With that being said, they can probably use re-capping to sound at their best. Ask how much use did they see. If they were powered on regularly, then the caps are in a much better shape vs amp being off for long periods. |
Yes. Don't believe everything you see on the internet. Most of it is rubbish. I bought my 1987 Krell KRS200s in the early 90s. A capacitor blew in 2007 (after 30 years) and I had them refurbished, mainly all new caps. Yes they do run very hot and in due course components will suffer. But they are running fine currently (pun intended), so on this amp refurbs come at possibly 25-30 year intervals, not 4 year. Of course if the manufacturer puts in cheap or sub-standard components then the period to breakdown could be much shorter. As I say to the Class D community: you get what you pay for. |
Vintage amps are cool. I listened to my first Levinson ML9 (100 wpc, Class A) connected to a monster sized pair of Apogee flat panel speakers. Woooweee, that amp and those speakers were a match made in heaven. The thing about though is that an Apogee flat panel speaker is "voiced" with an emphasis on midrange; this means a dry sounding amp would be perfectly matched to an Apogee because the neutral sounding amp plus a rich voiced speaker evens out. Back to vintage Class A amps, if you are looking to buy a Krell KMA, KSA, FPB or any sort of these Krells, all these amps are biased very high so they get HOT, like hot enough to cook an egg. When it comes to Levinson, a ML anything will need service because the capacitors are old, and old technology caps are not built as well as new Nichicons, Black Gate, Mundorf, etc. capacitors. If you absolutely have to buy a vintage Krell, Levinson, or other brand, call George Meyer AV in Los Angeles. They do tons of this capacitor replacement work, and they can tell you about specific amps and give you worse case scenario pricing to bring say an old amp back to life. The only Levinson I would personally get is a set of monoblocks, as in the 20.6. Everything else, meh, IMHO - hah! As for old Krell, I think the KSA50 and KSA100 are fairly musical, but for the money you spend to acquire and fix it, hell you can get something much better. |
I have Plinius SA 102 in dual mono at 125 watt pure class A stereo and 740 watts mono. Bought new in 2004. Still running great! Also Plinius SA 100 mk3 runs fine. Also a Cary 300b sei 8 watts pure class A tube amp running great. And ... A Dared VP 845 18 watt pure class A running great. All amplifiers need proper care and ventilation. Follow those simple requirements and they will last forever. What is needed is a little care and common sense. Know what speakers perform best woth a given amplifier. |
The weakest link in any electronics is ALWAYS the electrolytic capacitors (also maybe mechanical relays too, but for this specific conversation, they do not quite matter). One of the most important factors in their reliability is the temperature and the voltage they are exposed to. In theory, since class A amplifiers run hotter, all else being equal, it is possible that such capacitors may degrade and eventually break down, sooner than they would compared to other class of amplifiers. However, if the capacitors are chosen to be of a very hi quality (very long lifetimes & very high temperature & voltage capability), AND they are appropriately placed in the amplifier enclosure where they are not always exposed to high temperatures, they could in theory, last quite a long time. So, a blanket statement cannot be made but it is something which depends on a lot of factors. Take this capacitor for example, it is extremely well made, have a very long life and they can withstand high temperatures (37,000 hours at 105C). https://www.digikey.com/en/products/detail/kemet/PEG130MH3900QL1/4918903 If similar good components are used throughout, your amplifier will indeed last a long time too. |
mrmeaner13 posts06-13-2021 2:47amI have a glorious Class A Sugden A21SE and it never misses a beat, I contacted Sugden and asked them about having it serviced and he said it’s likely not to need looking at. In my opinion class A can’t be bettered. It is a fantastic amp! Mine is driving Tannoy Eatons with no issues. There are original a21’s still going strong 30 years later....Sugden, the very first commercially available solid state pure class A, since 1967. Some very ill informed people post here....notice the gigantic heat sinks that adorn both sides of the A21se...the amp is a brute! It is liquid, textured, detailed, holographic, and powerful...at only 30 watts/40 into 4 ohms....50% larger power supply than the previous A21 model, non se version. Built in the UK by one of only 12 employees...even comes with a tag indicating all who had their hands on it...worth every penny of the $3250 paid. When combined with Tannoy legacy, prestige, or gold series speakers, it is pure sonic bliss...end game combo. Add your own tubed phono preamp and it gets even better...Tavish Design makes some great phono preamps. |
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. |
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 |
No reason why a Class A amp of any rating can’t be designed withObviously 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 |
