Class D amplification and reliability

[Gervais Cote]

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?

I much prefer a class A or A/B amp powered by a wind turbine than a class D powered by a coal power plant !

 

[sq225917]

Class d is repairable just like mobile phones are, just most amp repairers don't have binocular scopes and hot air kit, they're still in the 70s.

I'm sure there's next to nothing smt Tony at Coherent can't fix.

 

[davidsrsb]

Packages with power pads underneath on multilayer PCBs are very difficult to change without floating off a load of components around them

 

[John]

I’ll let you know if my digital Sonos Amps fail. They are always on and have been sounding great. I think a lot of clever thought went into making them so I imagine they will see me out.

 

[Gervais Cote]

Packages with power pads underneath on multilayer PCBs are very difficult to change without floating off a load of components around them

And risky to break a snap fit board !

 

[Puggie]

Packages with power pads underneath on multilayer PCBs are very difficult to change without floating off a load of components around them

Focused infra red beam rather than using hot air. toast the component and just pick it off the board with tweezers/vac sucker. Providing the board has been assembled with some consistency and you don't have resistors etc with loads more solder on one pad than the other (if you do they may tombstone when heated) then you can do very localised repair with limited/no damage to the surrounding components. Hot air can work well but you can also blow small components off their pads if you are not careful. Saying that i could not be bothered trying to repair my Denon Ceol all in one job when the class d amp went south in it. I went and bought an older Musical Fidelity amp that had big stuff in I could get to easily. I find SMD stuff easy enough to work on, but much worse than through hole to trace and fault find. Without a decent schematic and board layout I probably wouldn't bother repairing a SMT board unless I thought it an easy fix or high value.

 

[firedog]

I don't get the problem. A lot of Class D amps are a PS, an input board, and the amp board. I think some combine the last two on one board.
What's to repair? If you get a serious fault you replace the faulty component. You can get a really high quality SQ amp for relatively little money, the boards don't cost that much.

I've had several and haven't had issues. I'm guessing some of the bad reputation is about much older models, the better newer ones don't have particular issues AFAIK.
Lots of powered subs also have Class D inside. I don't hear complaints about subs being particularly unreliable.

 

[earlofsodbury]

I'm sure there's next to nothing smt Tony at Coherent can't fix.

Of course, he's basically the Tony Stark of audio. Mere mortals may, however, tend to struggle a tiny bit at times...

 

[JimmyB]

Of course, a lot of these systems *could* probably be powered by an external power brick of the right spec......just retrofit a connector to the case and Bob's your cousin's dad.

 

[jobseeker]

External power bricks used to irritate me, but I can see the advantages.

 

[hifinutt]

Interesting to see 2 class d ref 500 monoblocks on eBay. Apparently one could not be repaired at coherent which I am slightly dubious about. However it does indicate that the mighty bel canto can fail sometimes...and these are icepower units .

 

[keiron99]

As someone with absolutely no technical knowledge whatsoever (but who has in the past had a few class D amps and been very impressed) shouldn't the fact that they produce negligible heat contribute to their longevity?

 

[Puggie]

The transistors are run efficiently and produce little heat. But other components with the high speed switching are worked very hard. We used to find certain resistors on Sony SMPS from a high end video camera we used to repair quite often failed I think due to the high power pulsed nature of how they were driven. Good component selection (MELF rather than traditional profile SMT resistors cope better with pulsed power and raising them off the pcb) can alleviate this, but it can be quite complex to get right.

Class D has less heat, but other issues.