Class D amp long term reliability

[mhardy6647]

Absolutely.

Just to add: The other benefit of buying robust gear is that it often becomes fashionable many years later and fetches more than one paid originally!

Win, win.

I keep hoping!

ahem... sorry, this is a serious topic and I actually do take it seriously (appearances to the contrary).
The true economy and environmental friendliness of these essentially (practically speaking) irreparable amplifier modules is not great when considered cradle-to-grave, and that is unfortunate for consumers and for the world (!) as a whole.

I do appreciate posts such as https://www.audiosciencereview.com/...2mp-cautionary-tale.63747/page-5#post-2388696
that make it very clear that the NC252MP module is a fifty-watt amplifier -- although bandwidth and distortion are not specified for this parameter.
Interesting that the footnote says this is "typically 1/5" of peak power. That's about a 7 dB difference, if I pushed the right buttons on the calculator.

 

[nc535]

As an EE, I know been exposed to reliability analyses and accelerated life testing of ICs. I know you can get more of the failures needed for the reliability analysis sooner simply by raising the test temperature. Regarding capacitor lifetimes, thermal management and derating are two primary ways of extending lifetime. Its entirely plausible that higher end amplifier modules would have higher reliability. That doesn't mean that the cost optimized modules can't be reliable enough if used well within their limits.

I'm interested in this discussion because I'm planning to make some 4 channel plate amps by bolting Hypex x MP modules to a large heatsink mounted vertically on the back of my speaker cabinet. Doing the analysis, I see that no matter how large the heatsink, I need vented airspace behind the module to allow convection generated air flow to limit the ambient temperature in the amplifier compartment. A fan would be even better, but I really don't want one, even though I know they can be quiet, having put replaced noisy fans in low end Pro amps with Noctuas.

To those using these amplifier modules, I would say that if the case is uncomfortably warm to your touch during normal operation, you are forewarned - add some heat sinking or a provide for some air movement.

 

[pma]

https://pmacura.cz/nc252mp_inside.JPG

Almost 4 years of flawless operation. Will be continuing monitoring. 4 years is still a baby amplifier .

 

[muad]

5 years would be very short life span for any serious amplifier. I would call it unreliable and never give a recommendation. Life span should be at least 20 years.

Yeah, I agree. I'm not happy right now and will not be buying another hypex amp.

 

[Buckeye Amps]

Yeah, I agree. I'm not happy right now and will not be buying another hypex amp.

Even if it is out of warranty, the amount they are asking for to replace the module is ridiculous.

 

[Chr1]

To me this is exactly the problem with these amplifiers. Modules fail and are very expensive to replace.

 

[Buckeye Amps]

To me this is exactly the problem with these amplifiers. Modules fail and are very expensive to replace.

I would say it depends on what very expensive means $200? $300? $500. Again, in terms of the NC252MP, it is nowhere near $400 anyways.

I am curious (genuinely, not rhetorically) to know what the average cost is to take a repairable Class A/B amp to a qualified repair shop/center.

 

[Power Pop 23]

I will be chagrined if the amplifiers I own based on the NC500 module fail within 10 years. I was expecting the imminent failure of my original Topping PA5 amplifier and thought a modular approach to design would be more reliable.

I have some backup amplifiers I can use. Maybe it's time to recharge some AA batteries and see how well my Dayton DTA-1 amplifier can drive a pair of Revel F206's.

 

[Power Pop 23]

I am curious (genuinely, not rhetorically) to know what the average cost is to take a repairable Class A/B amp to a qualified repair shop/center.

Agreed. Can we also get a head count on the number of people left who are qualified to do repairs ? A recently closed shop near me had a queue with a lead time that exceeded a year.

 

[respice finem]

Agreed. Can we also get a head count on the number of people left who are qualified to do repairs ? A recently closed shop near me had a queue with a lead time that exceeded a year.

I wonder if, for ecological reasons, a regulation might solve the problems, requiring repair by the manufacturer (or exchange for another refurbished part) for max. 50% cost of a new one, for 10 years? And publication of repair manuals etc. after a defined period of time. Maybe we would have fewer designs, but better longevity (IMHO).

 

[PristineSound]

I would say it depends on what very expensive means $200? $300? $500. Again, in terms of the NC252MP, it is nowhere near $400 anyways.

I am curious (genuinely, not rhetorically) to know what the average cost is to take a repairable Class A/B amp to a qualified repair shop/center.

In my 30 years in this hobby, going through over 2 dozen class AB amps, with one that is 30 years old in my possession (adcom) and one that's 50+ years old (Pioneer receiver) and few others that's over 20 years old now in the possession of friends and family.

I have not had a single one failed on me.

 

[Sokel]

I would say it depends on what very expensive means $200? $300? $500. Again, in terms of the NC252MP, it is nowhere near $400 anyways.

I am curious (genuinely, not rhetorically) to know what the average cost is to take a repairable Class A/B amp to a qualified repair shop/center.

Don't know if it's an index, but about 7 years ago a DC event upstream took away half a dozen of output devices (and their drivers) at one channel of a 400W/4 Ohm typical AB amp (think of something of Pass XA25 likes A/AB class which is DC coupled, not a bigger one like X350, etc ) .

Repair cost was 70 euro by a local guy there, my friend just left him a 100 euro bill and go.

It's more about finding people who fix this stuff, and where they are located.
Usually shipping is greater than repair cost, so having a steady dealer relationship helps a lot too, they usually know people who fix stuff, and depending the relatioship² most of the time is for free, exactly cause simple, well made gear like a class AB amp is hard to fail soon.

 

[Groove01]

I would say it depends on what very expensive means $200? $300? $500. Again, in terms of the NC252MP, it is nowhere near $400 anyways.

I am curious (genuinely, not rhetorically) to know what the average cost is to take a repairable Class A/B amp to a qualified repair shop/center.

It depends on where you live, how many qualified techs are in your local, and what needs to be repaired. (Or if you have a friend that’s a tech).

In my area, it’s like a $70 bench charge that goes towards the repair. Generally about $60 - $75/hr + parts. The parts are generally pretty cheap. I live in a large metro, so quite a few options.

I’ve actually never had a SS class A/B go bad though. (Had to get one re-biased once, cost $60).

Edit: I have quite a few old school class A/B car amps from the 90’s. I did have one go down (~2021), Rockford Fosgate Punch 60 DsM. Cost = $150 + $25 shipping. It had been in service since I bought it new, still cranks!

 

[PristineSound]

Yeah, I agree. I'm not happy right now and will not be buying another hypex amp.

Don't you think declaring this for the entire Hypex line is a bit extreme and unfair?

The reliability issues in question is only isolated to the MP line.

I have own the NC400 and now the NCx500, zero issues and I haven't came across many reports with other people who has issues.

I personally am very happy with my Apollon NCx500. For the money, I have ~240w into 8 ohms and ~420w into 4 ohms before the knee with overall low distortion and noise. It's frequency response is load and frequency invariant. It's withstands torture. And it's arguably the most luxurious Hypex amp on the market. To get what I have, I would need to buy two Benchmark AHB2 and run it in bridge.

 

[Keane16]

This thread has been really insightful. I've been trying to whittle down options and I think due to the discussion and details in post #100 I'll probably skip the NC252MP option.

View attachment 473306

As I'm in the UK I've been looking at the Nord VL MP NC252 which states, with no mention of peak or continuous:
• 2 x 150Wrms 8 Ohms
• 2 x 250Wrms 4 Ohms
• 2 x 180Wrms 2 Ohms

Another amp I've been looking at is the NAD C 379. Which states continuous output power into 8 Ohms:
• 80W (ref. 20 Hz-20 kHz at rated THD, both channels driven)

and IHF dynamic power:
• 8 ohms: 150W
• 4 ohms: 250W
• 2 ohms: 260W

The NAD I understand. There's an expected output and an output for peaks. Based on the Amp Spec in post #100 is the below more accurate in terms of the Nord NC252MP power output?

Continuous output (typically 1/5 of peak output):
• 2 x 50Wrms 4 Ohms

Peak output:
• 2 x 150Wrms 8 Ohms
• 2 x 250Wrms 4 Ohms
• 2 x 180Wrms 2 Ohms

Buckeye is the same for the Hypex NC252MP 2-Channel:
• 180 watts @ 2 ohm
• 250 watts @ 4 ohm
• 150 watts @ 8 ohm

Apollon Audio Hypex NC252MP Module Stereo Amplifier:
• 180W @ 2ohm
• 250W @ 4ohm
• 150W @ 8ohm

At first glance I thought the NAD had less power than the NC252MP alternatives, now I'm not sure that's the case after seeing the NC252MP tech spec.

 

[RickS]

I would say it depends on what very expensive means $200? $300? $500. Again, in terms of the NC252MP, it is nowhere near $400 anyways.

I am curious (genuinely, not rhetorically) to know what the average cost is to take a repairable Class A/B amp to a qualified repair shop/center.

Out of warranty repair, is going to be $100 or more depending on the failure. If unit is older, should probably get recapped and that adds up too. As you know, unless local, shipping often factors in significantly as well.

If the whole module is replaced, is going to be well over $100. I allow some credit for a module that may be repaired later or used for parts. For the former, again, shipping to Hypex for repair may be cost prohibitive notably for less expensive modules.

 

[wwenze]

Speaking of robust gear - the comparably cheap and simple chip amps in active speakers seem to fail less often (or is it my cognitive bias?)

There's a valid engineering reason

Their cost optimization is very sloppy

The start with a product that "completely doesn't work". Then the next jump is a product that "phew luckily it works" and I don't know how long it will last. And the optimization stops there. Most of the optimization is already done by the vendor.

Compare this to a company that wants to squeeze every possible profit margin while guaranteeing it lasts through warranty period with acceptable failure rate.

 

[gentlejax]

Agreed. Can we also get a head count on the number of people left who are qualified to do repairs ? A recently closed shop near me had a queue with a lead time that exceeded a year.

not only do you have to get on wait list but its going to be $300 minimum unless you do bare basic repair and not a restore. almost anyone though, can remove and replace one of these modules if they can be bought.

 

[Karmacoma]

I thought the design issue had been fixed in the more recent iterations, should I really expect mine not to last? You guys got me worried.
I'm very happy with it btw, it's as clean as it gets.

 

[Boredcarrot]

I have very mixed feelings about my Nord VL NC252MP, which I have had for more than a year. Sure it is very dynamic and has plenty of power and 'control', but I am not impressed by its (lack of) soundstaging. Channel seperation seems fine, as in left and right, but to me the thing just sounds so 2 dimentional. It's a damn shame because pairing it with my Topping DX5II makes a killer combo otherwise. But comparing it to my other amps, an audiolab 7000a and my current setup off 2x Exposure Electronics (semi-vintage) power amps with the DX5II as a preamp highlights the lack of 'depth' in comparison. Anyone else have this experience with their NC252?