Class D amp long term reliability

[boXem]

There is also Design for Manufacturing. This does not create the best possible product, but the most cost-effective product when it comes to the manufacturing process (and therefore the most profitable).

Well, the initial purpose of design for manufacturing is to ensure that things can be manufactured. And believe me, without it, design engineers can be quite creative...

What about light bulbs? As far as I know there was an illegal agreement between the big makers to limit their life span to 1000 hours. Very long ago...

First it is not because a sub-group has a bad behavior that the entire group has the same behavior. I come from an industrial sector that is currently being decimated by the EU because one cheated. So I am quite sensitive to the subject.
Second, the problem here is an anticompetitive behavior. None of these manufacturers spent a single cent getting their bulbs failing sooner. They just lowered the durability requirement, then the engineers saw an opportunity to decrease the BOM cost at the next spending review and here we go.

 

[caught gesture]

Well, the initial purpose of design for manufacturing is to ensure that things can be manufactured. And believe me, without it, design engineers can be quite creative...

First it is not because a sub-group has a bad behavior that the entire group has the same behavior. I come from an industrial sector that is currently being decimated by the EU because one cheated. So I am quite sensitive to the subject.
Second, the problem here is an anticompetitive behavior. None of these manufacturers spent a single cent getting their bulbs failing sooner. They just lowered the durability requirement, then the engineers saw an opportunity to decrease the BOM cost at the next spending review and here we go.

While what you write is true, DFM is also about minimising costs especially when it comes to the time taken to manufacture. This aspect of time is particularly relevant when deciding what materials to use. CNC machines, for example, can work much quicker with softer materials in general. That choice might not correlate with the best material choice for a particular application if one is to consider longevity or potential failure rates as being more important.

 

[boXem]

While what you write is true, DFM is also about minimising costs especially when it comes to the time taken to manufacture. This aspect of time is particularly relevant when deciding what materials to use. CNC machines, for example, can work much quicker with softer materials in general. That choice might not correlate with the best material choice for a particular application if one is to consider longevity or potential failure rates as being more important.

The best material for a particular application is the one that meets all requirements at the lowest cost. If the company "forgets" the durability requirements, well,... But then the problem is not DFM, it is the company's culture.

 

[EJ3]

Planned obsolescence is another conspiracy theory that tends to consider engineers as better than what they are.
It is already hard to design HW to not fail before some time while staying in the target costs. Do one really think that R&D budget will be spent to have stuff failing on purpose after a specified duration?

When there are printers that intentionally have a counting chip in them that stops the printer from working and some have a date coded ink that prevent the printer from operating if the ink is more than X months old. I experienced both of these type of planned failures while on ships at sea. A Russian hacker fixed the ones that had a chip whose only duty was to shut the printer down when it reached a certain count of pages printed. (He installed a program into the computer that operated the printer(s) which he had written to reset the counter). If it really happens, it is not a theory. Perhaps you should check out:

.

 

[boXem]

When there are printers that intentionally have a counting chip in them that stops the printer from working and some have a date coded ink that prevent the printer from operating if the ink is more than X months old. I experienced both of these type of planned failures while on ships at sea. A Russian hacker fixed the ones that had a chip whose only duty was to shut the printer down when it reached a certain count of pages printed. (He installed a program into the computer that operated the printer(s) which he had written to reset the counter). If it really happens, it is not a theory. Perhaps you should check out:

.

I have been technical manager for a product that was manufactured in quantities of about 1.2 millions per year. I don't need journos to tell me how things work in the industrial world.

 

[EJ3]

Planned obsolescence is another conspiracy theory that tends to consider engineers as better than what they are.
It is already hard to design HW to not fail before some time while staying in the target costs. Do one really think that R&D budget will be spent to have stuff failing on purpose after a specified duration?

When there are printers that intentionally have a counting chip in them that stops the printer from working and some have a date coded ink that prevent the printer from operating if the ink is more than X months old. I experienced both of these type of planned failures while on ships at sea. A Russian hacker fixed the ones that had a chip whose only duty was to shut the printer down when it reached a certain count of pages printed. (He installed a program into the computer that operated the printer(s) which he had written to reset the counter). If it really happens, it is not a theory. Perhaps you should check out

Boxem - I think you're spot on: it's not the engineers who are the evil-doers behind planned obsolescence, it's the bean counters, constantly squeezing the pennies out of designs to meet low price points.

This doesn't apply to the boutique, money-is-no-object, "audiophile" systems but for normal, consumer grade electronics, bingo. (Having spent a career in the tech industry, I saw it first hand. The product managers wielded very sharp spreadsheets.)

The the engineers mostly deal with the instructions that they are given. & many times they are given a price point or told to make it as cheap as possible. And our society has been long teaching us to "get the best deal". The deal does not include what it costs to dispose of the product. Therefore, in order to make money, the manufacturers must make things that are disposable. So that they can keep money rolling in to keep people employed. Very few are interested in making the "best possible" of something because they will likely have a spike of good sales for a few years (because for only a few is longevity a desire) & then go down to unemployment because we have been taught as a society to buy the latest whatever it is because it is a must have & you are not cool if you don't have the latest. (I am apparently not cool). But my most of my stuff (audio gear, vehicles, etc) are of very good quality & also repairable (many times by my own self).
My mother had a washing machine recently: We had a 2 inch flood that came in through our garage and the electronics in the washing machine died because they were mounted on the bottom of the machine.
That may not be planned obsolescence but clothes washing machines deal with water. Water flows downhill. So having the electronics on the bottom of the machine is (at best, if you are a uneducated child) just ignorant. I would even say that, because the washing machine is a known product that has been manufactured for may years, that (since the manufacturer is not a bunch of uneducated children) putting the electrical items on the bottom of a clothes washing machine could cause the company to be negligent in a wrongful electrocution death. Planning that stupid can only be intentional by omission. They did not look at the negative possibilities. Because if they did, the electrical parts would not be where the water is likely to be. Or, perhaps, they did plan it that way.

 

[EJ3]

I have been technical manager for a product that was manufactured in quantities of about 1.2 millions per year. I don't need journos to tell me how things work in the industrial world.

I have been in quality control and manufacturing from the 1980's-2021. I was a machinist for Cummins & then inspection on fuel injector housings for Robert Bosch (dealing in microns through high powered microscopes [and we manufactured quite a number of fuel injectors]), and in final quality control for Porsche, Mercedes & Boeing (as in the pilot gets on the plane & flies it to the owner that Boeing sold it to).
I will say that, during the time I was there, Porsche was the best at having things straightened out or outright scrapping things that were not right and people from the top would consult with the worker & quality when something came up as to how to keep it from reoccurring. Porsche is the only company that I regret that I did not just make a career of it there.
I presumed that you were versed in the subject and congratulate you for fortunately have had a pretty good experience over your career.
But there is another side, intentional or not.
What journalists dig up may or may not be 100% true (in fact, it is many times fabricated with just a tiny bit of truth or hidden advertising for a cause) but that truth comes from somewhere. Just as when one digs into legends, more often than not, there is at least a kernel of truth.

 

[Doodski]

truth comes from somewhere. Just as when one digs into legends, more often than not, there is at least a kernel of truth.

That's a cliche'. I suppose some people call it a strawman or some sort of stuff. I'm not into the the ogopogo or sasquatches running wild and free and I don't prescribe to the idea that truth comes from half truths and goobly gook.

 

[EJ3]

That's a cliche'. I suppose some people call it a strawman or some sort of stuff. I'm not into the the ogopogo or sasquatches running wild and free and I don't prescribe to the idea that truth comes from half truths and goobly gook.

I would like you to see the term "more often than not meaning 51% there is likely something there. That also means that 49% of the time there is likely nothing there. Your mileage may vary. I have never heard of an Ogopogo. I guess that I need to look it up. Having lived among native tribal people for more than 20 years of my life, I can say that there is some truth to some of the things they believe. And we are finding out that there are scientific reasons for some of their empirical knowledge. Please pay attention to the word "some".
An example: Willow tree bark turns into aspirin. The salicin in willow bark converts to salicylic acid. For centuries Natives knew it as a pain killer & anti-flammatory. Boiled as a tea, made into a tincture or just chewed. Today, we know that this makes a form of aspirin.

 

[thewas]

Having done many optimisation projects for different industries (mainly mechanical engineering) I know for example that cars are designed since ages for a specific lifetime. The only difference to the past is that with today's modelling, simulation and reliability engineering tools people can predict and design the lifetime of most parts much more precise and thus the failure of those parts will happen much closer all together which actually makes sense from engineering and sustainability point of view. 60 years ago the engineering wasn't as far so for example a VW Beetle gearbox was hugely overdimensioned (to several times the nominal engine torque) and would long outlive the engine (wear) and usually the chassis (corrosion) which might sound like "good old quality" but doesn't really make sense as it makes a product unnecessarily expensive and resources consuming.

From personal and sentimental point of view though, like @restorer-john, I love collecting and keeping alive good old overdimensioned classics like from my 1975 Mercedes to my 1980s Japanese hifi components, like he wrote they become something like "faithful old friends".

 

[TheWalkman]

I’d like to take a second and make a public service announcement: this is a fascinating discussion with input from what seems to be an incredibly broad range of life and career experiences.

This is what keeps me coming back to ASR!

Now back to our previously scheduled discussion…..

 

[UniPolar]

You have a lot of great experience ! Since this thread is about 'reliability', the words Porsche and Mercedes are not at the top of my list in that regard. And some of that may be related to anecdotal information, but after having several VW's in the late 70's & 80's, I still have an aversion to Audi/VW..
Reminds me of a quote by Click and Clack - 'Where there is smoke, there's a Saab'..

My next audio amp will likely be Class D because of the size to performance ratio and efficiency. Reliability would not be my primary reason for Class D.
..

I have been in quality control and manufacturing from the 1980's-2021. I was a machinist for Cummins & then inspection on fuel injector housings for Robert Bosch (dealing in microns through high powered microscopes [and we manufactured quite a number of fuel injectors]), and in final quality control for Porsche, Mercedes & Boeing (as in the pilot gets on the plane & flies it to the owner that Boeing sold it to).
I will say that, during the time I was there, Porsche was the best at having things straightened out or outright scrapping things that were not right and people from the top would consult with the worker & quality when something came up as to how to keep it from reoccurring. Porsche is the only company that I regret that I did not just make a career of it there.
I presumed that you were versed in the subject and congratulate you for fortunately have had a pretty good experience over your career.
But there is another side, intentional or not.
What journalists dig up may or may not be 100% true (in fact, it is many times fabricated with just a tiny bit of truth or hidden advertising for a cause) but that truth comes from somewhere. Just as when one digs into legends, more often than not, there is at least a kernel of truth.

 

[antennaguru]

You have a lot of great experience ! Since this thread is about 'reliability', the words Porsche and Mercedes are not at the top of my list in that regard. And some of that may be related to anecdotal information, but after having several VW's in the late 70's & 80's, I still have an aversion to Audi/VW..
Reminds me of a quote by Click and Clack - 'Where there is smoke, there's a Saab'..

My next audio amp will likely be Class D because of the size to performance ratio and efficiency. Reliability would not be my primary reason for Class D.
..

In my personal experience my Saab 900 was one of the most reliable cars I have ever owned. I drove it 300,000 miles with normal maintenance and no unusual failures, and the only reason I replaced it was because it had such high mileage and for my work I had places that I had to absolutely be, and be there on time. I have yet to get that sort of uneventful extended vehicle life out of the Toyota Avalon that immediately followed and then the Hondas that subsequently followed after my disappointment with the "flagship" Toyota that only gave me 200,000 miles with many unusual failures.

Of my six audio systems I use Class D amplification on my main system for the (external) subwoofer amplifiers only, and on one other less ambitious system as the main amplifier, only because the Class D modules are cheap and essentially disposable. They are IcePower 125ASX modules (a good model number for them because they cost $125). I assembled the modules into my casework/connectors and for some I added an input buffer stage. The Class AB amplifier on my main system sounds better, is vastly heavier, was much more expensive, and runs very hot - but it has done so reliably for two decades. I don't move it around so am not bothered by the size/weight, and my shelf is strong.

I also recently ordered a case of Rough Service 40W Incandescent Light Bulbs rated for 10,000 hours each. It seems that if you better support the filament they last a lot longer...

 

[EJ3]

In my personal experience my Saab 900 was one of the most reliable cars I have ever owned. I drove it 300,000 miles with normal maintenance and no unusual failures, and the only reason I replaced it was because it had such high mileage and for my work I had places that I had to absolutely be, and be there on time. I have yet to get that sort of uneventful extended vehicle life out of the Toyota Avalon that immediately followed and then the Hondas that subsequently followed after my disappointment with the "flagship" Toyota that only gave me 200,000 miles with many unusual failures.

Of my six audio systems I use Class D amplification on my main system for the (external) subwoofer amplifiers only, and on one other less ambitious system as the main amplifier, only because the Class D modules are cheap and essentially disposable. They are IcePower 125ASX modules (a good model number for them because they cost $125). I assembled the modules into my casework/connectors and for some I added an input buffer stage. The Class AB amplifier on my main system sounds better, is vastly heavier, was much more expensive, and runs very hot - but it has done so reliably for two decades. I don't move it around so am not bothered by the size/weight, and my shelf is strong.

I also recently ordered a case of Rough Service 40W Incandescent Light Bulbs rated for 10,000 hours each. It seems that if you better support the filament they last a lot longer...

The only car that I got well over 300,000 miles was a 1972 Ford Mustang Grande with a 351 Cleveland engine & a cast iron case FMX 3 speed (3rd was 1:1) automatic. It had the torque to weight ratio to pull the 3.00 final drive gear and keep the engine RPM down. The fuel economy wasn't great but you could fill the tank and know that you were going to get to the end of the tank without issues. I had changed the distributor to electronic & changed the intake & carburetor to a 600 CFM BBL. The death knell was the distributor gear. When it went out, I decided that I did not want to rebuild the engine & sold the car for some pretty good money. At the time I had already moved to island in Oceana & it made 0 sense to import a car to there. I bought a well used base 1996 Ford Ranger 2.3 L truck on one island & a 1980 Mercedes 300D on one of the others.
All of my 8 amps are from the mid-1980's to mid-1990's. 2 NAD 2100's, 5 NAD 2200's & 1 1977 Radio Shack Realistic SA -2000 (& 1 ADVENT 300 receiver) [one of my 2200's & my ADVENT 300 were both given test reviews here by Amirm]. All work fine, as I have done (or had done) as restorer John does.

 

[EJ3]

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.

Cost efficient at the point of sale, perhaps. Not time efficient for having to take the time out from enjoying your stereo, your life, your family, etc.
Time that you CANNOT get back. And not cost efficient for the people downstream, when you have disposed of many of these, not cost efficient for the environment: filling up the landfill with more junk (or the environmental cost of using trash ships to dump it in some other countries land.
The life cycle of the product seems abhorrently expensive to me. Lasting long, being rebuildable, reusable, re-purpose-able are important to me.

 

[ahofer]

Cost efficient at the point of sale, perhaps. Not time efficient for having to take the time out from enjoying your stereo, your life, your family, etc.
Time that you CANNOT get back. And not cost efficient for the people downstream, when you have disposed of many of these, not cost efficient for the environment: filling up the landfill with more junk (or the environmental cost of using trash ships to dump it in some other countries land.
The life cycle of the product seems abhorrently expensive to me. Lasting long, being rebuildable, reusable, re-purpose-able are important to me.

I think you've assumed a lot here that isn't yet in evidence.

 

[Bjorn]

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

We've spent a lot of time on reducing the heat on our Vera Audio amplifiers exactly in order to expand the life span. The PA400/1000 with Hypex modules uses temperature controlled fans which are non audible among other things that we have done to reduce the heat.

One moment, please...

We have shipped a unit to Prosoundtraining for a test and it will be forwared to Amir afterwards.

 

[rdenney]

…

I also recently ordered a case of Rough Service 40W Incandescent Light Bulbs rated for 10,000 hours each. It seems that if you better support the filament they last a lot longer...

Incandescent bulbs for use in traffic signals came in two power levels; the largest (for the current 12” indication) drew 133 watts. It was rated at 130 volts. Expected life was 8000 hours. The smaller bulbs (for 8” indications) had a life of 10,000 hours.

The LED modules that have replaced the bulb and reflector have an expected life (at 50% reduction in output) of 100,000 hours. And they draw one-tenth the power. They are more expensive to buy, but with lower lifecycle costs. Incandescent bulbs are no longer used by anyone to my knowledge.

Class D has the efficiency advantage going in to reduce lifecycle costs. But I turn my amps off when not in use, so idle draw for me is zero. Heat management is often an implementation issue, however. @restorer-john is there anything you would do to a new Hypex amp to minimize heat issues?

Rick “whose AB amps use unobtanium transistors, by the way” Denney

 

[DonH56]

There are many, many class AB amps in landfills, probably many millions if you count all the stereo receivers over the years that died and were tossed in the trash. I have some old, old gear for sentimental reasons, though I rarely use it now, but there some impediments to restoring old equipment. Figuring out the circuit and what failed, often without a schematic, finding old parts (often discontinued) or replacements, and having or finding someone with the knowledge, skill, and tools to do the repair can be daunting. I am in awe of what folk like @restorer-john do; maybe in another 167 years when I can retire I can do something similar. I used to repair and restore gear but my career took a different path, one that led to very little free time or desire to stare at a circuit when I got home after doing it all day long (albeit different circuits).

The component problem has gotten worse IME/IMO with higher integration; fortunately, power supply failures and discrete component failures (e.g. capacitors) seem most common and those are "easy" to fix. I suspect quite a few of us can remember Sanken modules with all the smoke let out, sometimes through the hole in the case... And the smell of a smoked transformer is something I can live without.

All that is a side argument to class D reliability, of course. My limited experience has been capacitors are what tend to die. I just replaced SMPS caps in a 10+ year old TV to get it running again. And there have been a long stream of bad video cards and computer monitors failing due to bad (generally under-spec'd) capacitors. I'd like to think we've learned and modern class D and SMPS designs are past that, especially given the focus on capacitor performance and reliability so there are oodles of good choices these days, but cynical experience says nay...

John's experience with that one amp is concerning. I am tempted to open up my Buckeye NC-252 build and take a look. I'd love to know if the problem is common or an outlier. That said, I have seen quite a few examples wherein it appear to me and my friendly mechanical/thermal engineer that the manufacturer failed to grasp that 80% or 90% efficient is not 100% and quite a few watts can still be wasted as heat even in a class D amp or (especially) SMPS design...

Friday musings - Don

 

[pma]

With high dv/dt you have more frequent capacitor failure, this is normal. Capacitors have to be thoroughly chosen and the good and special ones (rated at very high dv/dt) are expensive. Nothing for consumer electronics. In the PWM power supply for plasma gun, 300-500V/200kW we had a capacitor bank failure after 19 years of everyday run. So it goes.