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Class D amplification and reliability

L

leroyd

pfm Member
Class D designed amplification is becoming increasingly popular, yet some members on PFM have voiced concerns regarding these products being unrepairable, or prohibitively expensive to repair, when they develop a fault.
My primary experience with Class D amplification is within the realm of bass guitar and would have used a variety of class D amps in anger for over a decade, without ever having a problem
So I am wondering what the experiences of fellow Phishies with regard to having Class D amps repaired.
 
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They are both a little less reliable than conventional amps and MUCH more difficult to repair.

I've done a couple of high power bass amps in the past and whilst one had a reasonably easy to repair fault this is not the norm.... the other i had to buy in a complete new B & O ICE power module to replace the original.
SMD construction and multi layer boards don't help... to put it mildly! By and large if they fail the entire power amp board/module must be replaced... if it's still available...

I do this for a living and generally turn away class D repairs.
 
Mass market will go 100% Class D. The Man in the street Kef LSX / B&W zeppelin all they will ever need with built in Streaming & DSP
All in ones systems can already complete , Have a pair of Cabasse Akoya
Cabasse Pearl Akoya Powered DSP Loudspeaker - The Absolute Sound
Like industrial automation IPM/Igbt power transistors can switch huge loads & future D will be a single chip
Run active Speakers designed for 24/7 useage 4Kw & 26 channels of class D built in with no problem for a few years now . External 26 Class A/b monos would fill a several racks and double as a room heater

Class D already used in some very expensive amps these days
 
As I mentioned in another recent thread on class D amps, my experience with Hypex based class D amps is that, whilst they might be relatively inexpensive, they are not very reliable. I have used five Hypex based mono block amps over the last few years and all of them have suffered from power supply failures. They were all fixed by having the PSU boards replaced. I have since sold two of them and, out the remaining three, one suffered a repeat of the same PSU failure, another just stopped working and only the third is still working correctly. The two I sold, I believe, are still working.

I have since steered clear of class D.
 
Timcat said:
As I mentioned in another recent thread on class D amps, my experience with Hypex based class D amps is that, whilst they might be relatively inexpensive, they are not very reliable. I have used five Hypex based mono block amps over the last few years and all of them have suffered from power supply failures. They were all fixed by having the PSU boards replaced. I have since sold two of them and, out the remaining three, one suffered a repeat of the same PSU failure, another just stopped working and only the third is still working correctly. The two I sold, I believe, are still working.

I have since steered clear of class D.
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Erm.... that's nothing to do with amplifier class and everything to do with PSU failure! Probably the PSU's were SMPS.... which is very much the same technology as class D power amps. A class D amp is basically a SMPS in which the output power is modulated in step with the musical waveform. Everything said about SMPS pretty much applies to class D and vice versa.
 
Arkless Electronics said:
Erm.... that's nothing to do with amplifier class and everything to do with PSU failure! Probably the PSU's were SMPS.... which is very much the same technology as class D power amps. A class D amp is basically a SMPS in which the output power is modulated in step with the musical waveform. Everything said about SMPS pretty much applies to class D and vice versa.
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I stand corrected! In my defence I knew that the PSUs were SMPS and of the close relationship between class D amps and SMPS; I should have been more precise.
 
I ran some second hand nord ncores for a couple of years. Used daily no problems what so ever but the worry of them being expensive to repair was a contributing factor to going back to class a/b.

I have a dvd player with a suspected faulty smps that two engineers have looked at but not been able to diagnose/fix the problem
 
I think it’s a relevant concern. We spend all our pocket money on stuff we can only just afford, so we want it to keep working - but most amps are already class D and we just take them for granted, typically they keep on going and going.

As far as I can tell, the best amps have the best power supplies and they cost more. Doesn’t seem to matter which class it is. But if they do break and no schematics are available then you probably have a pretty paperweight. I almost acquired a Spectron musician which I would have loved to have heard, but in the end got a NuPrime amp that had been recently upgraded and could still be repaired if necessary.

If it weren’t for the heat I’d love class A, but I see them a bit like older V8’s. Exotic and wonderful but not something I should consider owning. Class D is admirable and competitive (and cool running!) but in the end I settled with Class AB - feels a bit like having a well specified Volkswagen rather than a Jag or a Tesla.
 
Sibbers said:
If it weren’t for the heat I’d love class A, but I see them a bit like older V8’s. Exotic and wonderful but not something I should consider owning. Class D is admirable and competitive (and cool running!) but in the end I settled with Class AB - feels a bit like having a well specified Volkswagen rather than a Jag or a Tesla.
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Oh, I don't know; I just ditched some class D amps in favour of a class A/B amp and I own a Tesla.
 
Years ago when everyone laughed at Class D as a serious Audio proposition I pretty much disagreed and stated that they would take the lions share of the market in years to come.

Apart from compactness, the relative lack of heat and increased efficiency compared to other topographies makes them less susceptible to component failure.

The main reason of their popularity is that they are less expensive to produce, therefore more profitable.
 
Hooch500 said:
Apart from compactness, the relative lack of heat and increased efficiency compared to other topographies makes them less susceptible to component failure.
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Not my experience with the SMPS used in the class D amps I had. They ran hot and failed!
 
Hooch500 said:
less susceptible to component failure.
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Only if well designed and component choices aren't skimped on for cost....but that's the same with all things.
We seem to not bat an eyelid at recapping amps and linear power supplies but when the caps go on the SMPS designs they're replaced. (the boards) in full. You can design for both reliability and maintainability but that's takes more money up front.
 
Timcat said:
Not my experience with the SMPS used in the class D amps I had. They ran hot and failed!
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SMPS are used in many Class A/B amps including the much touted Sony Esprit series donkeys years ago. If Jed thinks some Class D amps are unfixable he needs to take a look in one of those. SMPS or linear can be used with Class D. There are good, bad and ugly in all walks of life and amplifiers are no exception.
 
Hooch500 said:
SMPS are used in many Class A/B amps including the much touted Sony Esprit series donkeys years ago. If Jed thinks some Class D amps are unfixable he needs to take a look in one of those. SMPS or linear can be used with Class D. There are good, bad and ugly in all walks of life and amplifiers are no exception.
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The SMPS in my Hypex based amps were unfixable other than by whole board replacement. In fairness, you are probably right to say that there are good, bad and ugly amps and power supplies of all types, it's just that I have been put off class D amplifiers in general as a result of my experience with Hypex based amps and, specifically, their SMPS.
 
Those Hypex psu are about as well known for throwing in the towel as early linn smps were. I have no doubt that class d is the future for the majority of uses, its just not there for me yet.
 
Arkless Electronics said:
I do this for a living and generally turn away class D repairs.
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I find this statement very telling. I doubt you're alone in feeling this way. This consideration massively undermines the supposed 'Green' credentials of switchmode amps.

By contrast, my otherwise-irresponsible class-A power amp is now 13 years old and working faultlessly - if it fails it can be repaired despite using out-of-production output transistors - if in time the manufacturer no longer holds those, the amp can be quite easily re-configured by swapping a few component values &c to work with slightly different silicon, it stands every chance of outliving me.

Product longevity is currently the loveless orphan of the 'green revolution', but as we switch to greener sources of power, power consumption will start to have less environmental impact than the wasteful use of more-tangible resources will...

Makes me wonder if class-D has a truly long-term future?
 
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