Class D amp long term reliability

[sophie smith]

Hi,

Looking for 2 channel amp to play a few hours 3-4 days a week. Would like to keep it for the next 10-15 years. Are class D amps today reliable enough to last that long without issues? Or should I go with AB amp? Don't really care one way or the other, but obviously my choice would be limited.

Are there any modules that are more reliable than others as far as D-amps go?

Thanks

 

[dfuller]

As with anything electronic, it entirely depends on the components used. The stuff that has a "lifespan" is mostly electrolytic capacitors. Purifi Eigentakt modules use good quality capacitors on top of the other good quality overspecced components. The only real weakness, per se, is the Hypex power supply usually used with them. They're known to use less-than-amazing quality capacitors from brands such as Su'scon. Still, if not stuck in a hot box it will still last quite a while before needing recapping.

 

[Matias]

There is a loooong thread about capacitors in Hypex power supplied here:
https://www.audiosciencereview.com/.../apollon-hypex-nc2k-amplifier-teardown.16920/

 

[dfuller]

There is a loooong thread about capacitors in Hypex power supplied here:
https://www.audiosciencereview.com/.../apollon-hypex-nc2k-amplifier-teardown.16920/

Quite a bit of pointless and rather childish arguing, too.

TL;DR: Hypex doesn't use particularly great quality caps in their power supplies, but they should still give years of reliable service - just not as many as if there were better parts.

 

[ahofer]

I don't think we have enough years with the new modules to fully understand reliability. But they are cheaper and more energy efficient, so even if they don't last as long, they may be more cost-efficient.

I've had an nc252-based design for a couple of years with no problems.

 

[Matias]

Its not like they are expensive to replace anyway: 180 euros for a SMPS1200 power supply for example.
https://www.diyclassd.com/product/smps1200a400/10

 

[egellings]

In a relatively cool switchmode amplifier setting, The caps, if designed (low ESR, ESL) for switchmode work, should have a long & happy life. I feel sorry for 'lytics stuck in a tube amp, though.

 

[Doodski]

Purifi Eigentakt modules use good quality capacitors on top of the other good quality overspecced components.

How do we know those things? Are they facts or are you just saying it.

 

[egellings]

We get to know these things by knowing what we are talking about (studying the topic beforehand), and then looking at the evidence concerning the talked about subject matter, and then comparing to see if the rhetoric and the evidence coincide. If not, we toss the talk and try again. Evidence rules!

 

[NTK]

The prototype Purifi 1ET400A amiplifer Amir reviewed (link) had Rubycon caps.

However, the current picture in Purifi's web (link) shows that they are replaced by a different brand (different vent cap marking).

 

[DVDdoug]

Are class D amps today reliable enough to last that long without issues? Or should I go with AB amp?

I don't know if there's a difference as long as both are well-designed and well-built. Class-D amps are more complicated so "there's more that can go wrong" but they run cooler and most power amplifier failures are heat related. ...I've got a vehicle with the (aftermarket) amps located in a place where they can overheat. I've had a couple of bass amps fail (regular-old Class A/B) and now it has a Class-D, which runs a LOT cooler. Hopefully this one will be more reliable.

Electronic failures in solid state electronics are pretty-random unless there is a defect and it fails right away. The theory is - It's just as likely to fail in the 50th week as in the 1st week.

Electrolytic capacitors can age, but from what I understand the capacitance value tends to drop and unless the capacitor is part of a filter (high-pass or low-pass) or some other "tuned circuit", the value is rarely critical. I've worked in electronics for a LONG time and I don't remember EVER seeing an item returned with a failed capacitor! ...Most capacitor failures I've seen are reversed tantalums that blow-up (sometimes literally) during testing & burn-in before the item is shipped. Most returns I see are a fried output chip where the customer has probably sorted something out, but occasionally we get a dead CPU chip for "no known reason".

At work I've got an OLD Windows 98 computer (I think its a Pentium chip but it could be a 486) as part of a test setup and it's still working (the hard drive may have been changed once or twice). Of course that's unusual and I've had lots of computers die, but I've probably upgraded/replaced more computers that were still working than I've replaced because they died.

At home I've got an OLD power amplifier (Dynaco Stereo-120) that failed a couple of times (transistors blowing) and when the parts were no longer available I rebuilt the "guts", keeping the power transformer and some other components, including the "big" power supply capacitor and the output capacitors (it has a single-ended power supply, I didn't change that, so there are output capacitors to block the DC from the speakers). It was re-built 30 or 40 years ago and the "new design" has turned-out to be more reliable than the original and I'm still using it (currently as a subwoofer amp.)

 

[sophie smith]

Any one knows about the "Orchard Audio" internals? He uses GaN modules, with great measurements posted by him. He also sells boards only. Are those quite reliable?

 

[Deleted member 21219]

I view reliability somewhat differently than perhaps a few here. In my mind, reliability is not incidental or accidental. It occurs when that quality is seen as a primary and desirable characteristic. In other words, you don't design for efficiency, or effectiveness, and have reliability just happen. You have to design for reliability at the same time as efficiency or effectiveness, and then see how efficient you can make the device, or how effective it can become without reduction of that necessary reliability.

I don't see that happening today. Not in audio, and not in anything else. Jim Taylor

 

[TheWalkman]

Asking about the longevity of an amp is, IMHO, like asking how many miles you should expect a car to last. A guy I cycle with had a late ‘90s model Civic last over 400k miles as an every day driver. (He grew up on a dairy farm and knowing him, the oil and filters were changed, but I doubt the car was babied at all.). He gave the car to his granddaughter five years ago. She totaled it within six months.

As the saying goes, “your mileage may vary.”

For $60 - the price of an average dinner out with a couple of beers in the US, buy an Aiyima A04/ A07, run it hard (with some air circulation around the case), hook up a streamer or your cellphone and enjoy. If it lasts 2 years or twenty, be satisfied.

In the grand scheme of things, worrying about longevity isn’t worth losing sleep over. Enjoy it and don’t look back.

 

[sophie smith]

I view reliability somewhat differently than perhaps a few here. In my mind, reliability is not incidental or accidental. It occurs when that quality is seen as a primary and desirable characteristic. In other words, you don't design for efficiency, or effectiveness, and have reliability just happen. You have to design for reliability at the same time as efficiency or effectiveness, and then see how efficient you can make the device, or how effective it can become without reduction of that necessary reliability.

I don't see that happening today. Not in audio, and not in anything else. Jim Taylor

Completely agree, although Toyota still makes pretty darn reliable cars....
Large/mass manufacturers, likely you are right. But small companies.... That is why I asked about Orchard audio.

 

[JJB70]

Most things follow a bathtub curve for failure, with increased failure rate right at the start of an life after initial delivery and then after an interval as end of life approaches (or as time for major overhaul approaches). The length between the two peaks is, however, variable and higher quality items can be expected to push the end further away from the beginning. And there are always random failures.

 

[UniPolar]

I'd think that low heat would mean long life, but that's beyond my pay grade.. So, to be safe, I would buy ( and expect to maybe pay more ) for the Class D amp from a company that has established longevity and has a generous warranty.

Some 'assemblers' of class D amps do not have either... And if that assembler goes belly up, I suspect the 'warranty' on the Hypex/Purifi amp module itself would be difficult to 'claim'..

And there are also possible limitations of liability which I'll not dwell on..
.

 

[jtwrace]

FWIW, my Hypex NC502MP's have been powered on 24/7 for nearly 5 years.

*All equipment is plugged into a Zero Surge unit.

 

[julian_hughes]

If you think about it then probably you've already been using Class D amps for many years, in soundbars, laptops, portable devices, phones, DAPs etc. There's no intrinsic reliability issue; this stuff works for many years.

 

[EJ3]

Choose wisely: This was my choice in the late 1980's and I am still using them.
NAD 2200 Power Amplifier PE (an AB amp)
Date of manufacture : Jan 87 - Feb 89
(I own 5 of these & one earlier non PE [Power Envelope or for those down under: Power Tracking]). I typically run one for my pair of subs in a 2 ohm configuration. And one on each channel in a bridged mono 4 ohm configuration. Yes, that takes up 3. Sometimes I also run one per sub in a bridged mono 4 ohm configuration. The spare amp rotates in & out of the system or does duty on other projects. All are subject to being replaced by the spare for various periods of time.
These have traveled the world with me (USA, OCEANA, Islands in the Indian Ocean, Saipan, Guam and many other places and operated under many different conditions). In 2016 I decided to have a look see, figuring that they were long in the tooth. Many things were done to bring them to the best specs possible (since I had commissioned to have them gone through) without outright changing any of the circuitry. The results can be seen in Amir's NAD 2200 Review. The only outright failure that I ever had was a speaker relay (from wear). There are the questions of will parts for whatever amplifier that you choose be available in 10 or 15 years? At what cost? And will there be technicians that can repair it?
IMHO: It is worth it to spend more money up front to have better quality/reliability of the parts than to be down & waiting to upgrade the lesser parts in an inexpensive amp. As to the box it is in, if you are not going to use it as a seat, it doesn't need to be billet.
I don't own a class D yet, as I am concerned about reliability.
POWER AMP SECTION
Continuous output power into 8Ω *
Rated distortion
(THD 20Hz - 20kHz)
Clipping power
(maximum continuous power per channel)
IHF Dynamic headroom at 8Ω
IHF dynamic power
(maximum short term power per channel)
Damping factor
(ref. 8Ω, 50Hz)
Input impedance
Input sensitivity
(for rated power into 8Ω)
Frequency response
Signal/noise ratio
THD
(20Hz - 20kHz)
Bridged Mode
Continuous output power into 8Ω *
IHF Dynamic headroom at 8Ω
IHF dynamic power
(maximum short term power per channel)
PHYSICAL SPECIFICATIONS
Dimensions
(W x H x D)
Net weight
Shipping weight
Power consumption
(120 ~ 240V, 50/60Hz)
* Minimum power per channel, 20Hz - 20kHz, both channels driven with no more than rated distortion.
Dimensions are of unit's cabinet without attached feet; add up to 18mm for total height.
Dimension depth excludes terminals, sockets, controls and buttons.
© NAD Electronics. All rights reserved. E & OE
100W (20dBW)
0.03%
140W
+6dB
8Ω
400W (26dBW)
4Ω
600W (28dBW)
2Ω
800W (29dBW)
>100
25kΩ / 1000pF
700mV
3Hz - 80kHz / +0, -3dBdB
ref. 1W
>91dB
ref. rated power
>111dB
<0.03%
400W (26dBW)
+5dB
8Ω
1.2kW (31dBW)
4Ω
1.6kW (32dBW)
420 x 123 x 370mm
12.5kg
14kg
770W