Class D amp long term reliability

[Chrispy]

The hypothesis here is the plate amp problem seems to be uniquely Class D. Could just as easily be lower quality in subwoofer plate amps regardless of what class they are. I have 2 older Dayton audio Class AB plate amps that have failed over the last couple of decades. These were likely higher quality amps than the usual stuff that goes into mass market subwoofers too…

I have also moved towards active speakers and have used external Class D amplifiers without any issues. My newer subwoofers are external amps as well. To deal with the shock and vibration from powerful drivers, a plate amplifier needs special design considerations that add cost. If these additional considerations are skipped to meet price targets, lower reliability will result (regardless of the class of the amplifier).

Good point, I think AB class in such situations can be problematic, too.....one of my plate amp failures was an AB.....

 

[antennaguru]

The hypothesis here is the plate amp problem seems to be uniquely Class D. Could just as easily be lower quality in subwoofer plate amps regardless of what class they are. I have 2 older Dayton audio Class AB plate amps that have failed over the last couple of decades. These were likely higher quality amps than the usual stuff that goes into mass market subwoofers too…

I have also moved towards active speakers and have used external Class D amplifiers without any issues. My newer subwoofers are external amps as well. To deal with the shock and vibration from powerful drivers, a plate amplifier needs special design considerations that add cost. If these additional considerations are skipped to meet price targets, lower reliability will result (regardless of the class of the amplifier).

Interesting that your definition of active speakers is my definition of passive speakers - aka speakers WITHOUT built-in amplification.

My IRS Beta subs have an external controller and 2 separate external amplifiers, and I consider them passive subs that use external amplifiers along with an external amplifier controller using accelerometers on the woofers.

 

[tmtomh]

Interesting that your definition of active speakers is my definition of passive speakers - aka speakers WITHOUT built-in amplification.

My IRS Beta subs have an external controller and 2 separate external amplifiers, and I consider them passive subs that use external amplifiers along with an external amplifier controller using accelerometers on the woofers.

We’ve been through this definition discussion before in another thread.

A speaker system with external amplification can be - and probably should be - described as an active speaker system if the crossover network comes before the amplification.

Conversely, there are powered speakers with built-in amps that shouldn’t be described as active, because their crossovers come after the amplification - the crossover network is passive.

 

[GXAlan]

What with the well known poor reliability "reputation" of plate amps, I am hard pressed to understand why there is so much enthusiasm here on this site for active speakers.

+100

The question, which is a fair one, is

1) Are Class D amplifiers less reliable than Class A/AB amplifiers?

OR

2) Are amplifiers of the present day less reliable than amplifiers of yester-decade and you have more Class D amplifiers in the modern day?

The Sony TA-N88 is one Class D amplifier from 1977 which has surviving specimens

Sony TA-N88B, V-FET for sale.

The Soncoz SGP1 has had early failures even though its class AB
https://audiosciencereview.com/foru...p1-stereo-amplifier-review.47554/post-1760502

Plate amps are after all specifically designed for use in active speakers, with plate amps being the most common failure point of active speakers (unless they also take out the driver(s) as well when they fail). I recall there even was a thread on this site questioning why passive speakers are even made anymore, to which I will simply reiterate that active speakers are destined to have short lives compared to passive speakers. When the plate amp in an active speaker does fail the owner will need to find a replacement that fits the hole left behind by the dead plate amp.

+1000. I have the JBL 708P which has inconsistent track record of warranty support.

For me, I went with Meyer Sound since
at least they have the reputation of being able to support their products for decades, even those out of production. During Sidney Harman’s tenure, JBL Professional had the same reputation — so time will tell how Meyer Sound will work after John and Helen Meyer retire…

 

[antennaguru]

We’ve been through this definition discussion before in another thread.

A speaker system with external amplification can be - and probably should be - described as an active speaker system if the crossover network comes before the amplification.

Conversely, there are powered speakers with built-in amps that shouldn’t be described as active, because their crossovers come after the amplification - the crossover network is passive.

Well then I simply don't agree with this definition. By your definition every full range speaker that has no crossover has thereby become an "active" speaker - since by your definition there is no crossover between the amplifier and the speaker. My excellent AGA Strada 2 speakers are the main speakers in the system with the AGA sub plate amp that failed and was in fact still purchasable from the OEM. They are crossover-less multi driver main speakers.

Furthermore, simple car stereo full range crossover-less speakers would become "active" by your new definition. Same thing with cheap compact stereos.

To be sure, sound reinforcement PA systems using mid-woofers with crossover-less piezo tweeters becomes an active system by your definition.

Finally, the Compact Line Array speakers I built with long columns of full range speakers would become active by your definition.

No, myself and the rest of the world outside of a few people on this site will be sticking with the normal definition that active speakers are speakers with built-in amplifiers, and that passive speakers use external amplifiers.

 

[dfuller]

Okay, we're not doing this again. A full range single driver speaker can be active or passive, depending on whether a filter network is applied before or after the amplifier. This is not complicated.


Your aversion to plate amps is certainly well founded based on your experience, but mine has been very different. I have seen far more driver failures in passives (especially tweeters) than I have plate amp failures in actives.

Well then I simply don't agree with this definition. By your definition every full range speaker that has no crossover has thereby become an "active" speaker - since by your definition there is no crossover between the amplifier and the speaker. My excellent AGA Strada 2 speakers are the main speakers in the system with the AGA sub plate amp that failed and was in fact still purchasable from the OEM. They are crossover-less multi driver main speakers.

Furthermore, simple car stereo full range crossover-less speakers would become "active" by your new definition. Same thing with cheap compact stereos.

To be sure, sound reinforcement PA systems using mid-woofers with crossover-less piezo tweeters becomes an active system by your definition.

Finally, the Compact Line Array speakers I built with long columns of full range speakers would become active by your definition.

No, myself and the rest of the world outside of a few people on this site will be sticking with the normal definition that active speakers are speakers with built-in amplifiers, and that passive speakers use external amplifiers.

 

[antennaguru]

Okay, we're not doing this again. A full range single driver speaker can be active or passive, depending on whether a filter network is applied before or after the amplifier. This is not complicated.


Your aversion to plate amps is certainly well founded based on your experience, but mine has been very different. I have seen far more driver failures in passives (especially tweeters) than I have plate amp failures in actives.

Well, I didn't "do this" before and I will not accept this flawed definition - however you happen to feel about it. Sounds like that must have been a frustrating thread, and I can see why you feel that way.

A filter network is a cross-over, and many full range driver implementations do not use crossovers at all. What make a crossover-less full range driver an active speaker? If you put a plate amp in a speaker with this full range driver, then it's an active speaker. If the amp is external to the speaker, then it's not. Simple as that.

 

[Philbo King]

The hypothesis here is the plate amp problem seems to be uniquely Class D. Could just as easily be lower quality in subwoofer plate amps regardless of what class they are. I have 2 older Dayton audio Class AB plate amps that have failed over the last couple of decades. These were likely higher quality amps than the usual stuff that goes into mass market subwoofers too…

I have also moved towards active speakers and have used external Class D amplifiers without any issues. My newer subwoofers are external amps as well. To deal with the shock and vibration from powerful drivers, a plate amplifier needs special design considerations that add cost. If these additional considerations are skipped to meet price targets, lower reliability will result (regardless of the class of the amplifier).

Yep. Staking down large parts with silicone RTV that are subjected to vibration is always a good idea, provided it doesn't increase heat buildup.

 

[dfuller]

Yep. Staking down large parts with silicone RTV that are subjected to vibration is always a good idea, provided it doesn't increase heat buildup.

Correct. This is especially a good idea with big electrolytics - even though snap-in terminals have decent mechanical strength, they can still easily break solder joints over time.

A filter network is a cross-over,

Not necessarily. Crossover implies more than one band-limited driver. Hence why I said filter network and not crossover, notches or equalization for baffle step etc are independent of band limiting.

What make a crossover-less full range driver an active speaker?

It doesn't. It's just an amp connected directly to a driver. So I'd call it a powered speaker. Rather like a guitar amp in that department... thoughts for later.

If you put a plate amp in a speaker with this full range driver, then it's an active speaker. If the amp is external to the speaker, then it's not. Simple as that.

This definition falls apart with multi-way speakers. That's why it doesn't work.
A powered speaker has a speaker level filter network (if present) with a full range amp in the box. This is usually limited to cheaper multimedia speakers where both channels of amplification are in the same box, with one channel being run to the other totally passive speaker.

Active speakers on the other hand require the crossover(s) and any filters be prior to amplification, necessitating at least biamping (since the amps are fed a band-limited signal). Whether or not the amps and crossover are in the same box is inconsequential, as most studios that run active flush-mounted monitors remote mount the amps for heat reasons.

Then you have weird edge cases like Barefoot Footprints, where they're active, but only biamped despite being three ways - they use a passive crossover between mid and tweeter, but active between woofer and mid/tweeter.

 

[Geert]

A speaker system with external amplification can be - and probably should be - described as an active speaker system if the crossover network comes before the amplification.

What make a crossover-less full range driver an active speaker? If you put a plate amp in a speaker with this full range driver, then it's an active speaker. If the amp is external to the speaker, then it's not. Simple as that.

Active speakers system versus active speaker... Active speaker systems existed decades before active speakers became popular.

 

[sigbergaudio]

1) Are Class D amplifiers less reliable than Class A/AB amplifiers?

We've been through this, maybe even earlier in this thread. Old Class AB subwoofer amplifiers were not very reliable, to the point that they were partly to blame for giving Class D a bad reputation in the first place, since Class D was introduced in subwoofers earlier than they were generally accepted for full range use.

So no, Class D is not inherently less reliable than Class AB.

Subwoofer plate amps regardless of class are often cheap designs with insufficient cooling, so their lifespan may vary. Plate amps in general can be made good or bad, so they may last a lifetime if made right, and it doesn't necessarily have to be connected to cost either.

My personal anecdotal example is cheap logitech 2.1 systems built for use with computers, they seem to last forever. I have one that cost maybe 200$ for speakers + sub and it's at least 15 years still going strong. Anecdotal examples like this doesn't tell us much either way, as we have no information about failure rate.

 

[Sokel]

Well, I didn't "do this" before and I will not accept this flawed definition - however you happen to feel about it. Sounds like that must have been a frustrating thread, and I can see why you feel that way.

A filter network is a cross-over, and many full range driver implementations do not use crossovers at all. What make a crossover-less full range driver an active speaker? If you put a plate amp in a speaker with this full range driver, then it's an active speaker. If the amp is external to the speaker, then it's not. Simple as that.

Are Genelec 8381 active or not?

 

[Geert]

Are Genelec 8381 active or not?

They're an active speaker system. There are no active components in the speaker itself. "A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole".

 

[Sokel]

We're in 2023 and everything these days are made to meet certain conditions,everyone can see them and decide,vibration ones included.
One popular plate amp is the Hypex one who uses NCxxxMP modules (fusion series).I guess these specs are in their spreadsheets (I don't have them but I have the icepower ones and they are there) :



So it's up to the engineers to choose what fits and ensures longevity,specs are available by the truckloads these days.
Warnings are there to see.

 

[Rick Sykora]

Yep. Staking down large parts with silicone RTV that are subjected to vibration is always a good idea, provided it doesn't increase heat buildup.

From my earlier days in automation recall there is a bit more to it than just dampening with sealants. Component spacing and solder pad sizes come to mind. Then there is the testing to verify and possibly address any shortcomings. May be able to simulate it these days but not sure how accurate it would be.

All of the extra considerations added time and expense to the design. Probably should mention heat as plays a major role in reliability too. Would expect that Class D has advantages in making designs that are lighter and have better thermals. If done well, would expect it to be the better technology for embedded amplifier speakers.

 

[Tovarich007]

Well then I simply don't agree with this definition. By your definition every full range speaker that has no crossover has thereby become an "active" speaker - since by your definition there is no crossover between the amplifier and the speaker. My excellent AGA Strada 2 speakers are the main speakers in the system with the AGA sub plate amp that failed and was in fact still purchasable from the OEM. They are crossover-less multi driver main speakers.

Furthermore, simple car stereo full range crossover-less speakers would become "active" by your new definition. Same thing with cheap compact stereos.

To be sure, sound reinforcement PA systems using mid-woofers with crossover-less piezo tweeters becomes an active system by your definition.

Finally, the Compact Line Array speakers I built with long columns of full range speakers would become active by your definition.

No, myself and the rest of the world outside of a few people on this site will be sticking with the normal definition that active speakers are speakers with built-in amplifiers, and that passive speakers use external amplifiers.

Please, the subject of this thread isn't the definition of active or passive speakers, this have been discussed before in another thread. So go back to the subject : the reliability of class D amps, should they be implemented in plate amps or not, or be used with active or passive speakers..

 

[Roland68]

Yet another failed Class D subwoofer plate amp! This latest one was on a system in our mountain house and was purchased new directly from the manufacturer, Anthony Gallo Acoustics in 2014. It was never abused and was sparingly used on a very nice sounding stereo system with passive wall mounted AGA Strada 2 main speakers ($2000 for the pair). The AGA TR3 subwoofer had cost $1000 new 9 years ago, and my KUDOS to AGA as they are still able to support the customer with a replacement plate amp for $210 shipped. I'm looking forward to receiving and installing it so I can get that system fully operational again.

This latest Class D amp failure brings my total of failed subwoofer plate amps up to 4 out of 6 subs. 3 of those 4 failures were Class D subwoofer plate amp failures, and 1 of the 4 failures was a Class AB subwoofer plate amp failure. The remaining 2 subs don't use plate amps, and have had no failures of any kind. In other words every single plate amp active speaker (all were subwoofers) that I own has failed. One even took out its woofer as collateral damage when it died. This latest one lasted the longest at 9 years before failing, and this one is the only one that is still being supported by the OEM. JBL and EV were not able to support providing replacement plate amps for their subs, and I had to adapt alternative generic plate amps from Parts Express to those subs, which required me making sheet metal filler plates in my metal shop to adapt the OEM sub cutouts (holes) to the dimensions of the replacement plate amps - as there is zero standardization in plate amp dimensions.

Upon visual inspection of this latest failed Class D plate amp I can see a few caps that look bad, but there is a lot of brown Glyptol and white RTV on the board securing components and making board level component replacements too cumbersome an exercise. Thankfully the woofer is fine.

What all of these plate amp failures have in common is that they all lived their lives inside a speaker cabinet with poor ventilation and plenty of vibration. This just adds further fuel to my belief that active speakers, subs or mains, are ALL destined to fail in a vastly shorter timeframe than passive speakers. These failures will be the electronics, unless they fail in a manner that also kills the driver. To be sure, I own several sets of passive main speakers that are over 30 years old with no failures.

I am very appreciative that Anthony Gallo Acoustics is able to support providing a replacement plate amp for my 9 year old AGA subwoofer!!! They are very customer focused, unlike JBL and EV who could not support providing replacement plate amps for subs that were quite younger than 9 when they failed. Anthony Gallo Acoustics was acquired late in 2022 by Pulse-Eight.

This view is very one-sided and certainly wrong in relation to the entire market.
I can't tell you how many broken active subwoofers with traditional transistor technology I've seen in my life. But over 90% of them are defective for the same reason as those with Class D technology, namely cheap construction and even cheaper components.
You only need to look at sales of defective subwoofer amplifiers over the last few years, or decades, across all platforms, and that's just a fraction.

The big manufacturers, such as NAD and Pioneer, have been showing for a long time that Class D works and is not prone to failures.

For the past 3 years, I have been advising users with defective subwoofers to repair them using inexpensive Class D boards and high-quality Meanwell power supplies. So far it has held up without a single failure.

 

[martin900]

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

No, stay away if you want a truly reliable amp. Class D + SMPS eat through the electrolytic caps due to ripple/high frequency, speaking from experience.
Get a lo/mid biased class AB amp that's known for using good quality parts and which isn't notorious for running hot (think Denon PMA1500/2000 series, these run hella hot on the drivers).

 

[Roland68]

No, stay away if you want a truly reliable amp. Class D + SMPS eat through the electrolytic caps due to ripple/high frequency, speaking from experience.
Get a lo/mid biased class AB amp that's known for using good quality parts and which isn't notorious for running hot (think Denon PMA1500/2000 series, these run hella hot on the drivers).

Unfortunately, this is another prejudice.
All you have to do is look inside the computer area to see what the problem is. Motherboards and power supplies that fail in the first year are in stark contrast to high-end parts from Supermicro, for example, which are still running after 10 years even in extreme operation.
Difference? There are capacitors installed that cost more to purchase for industrial purposes than the complete Motherboards and power supplies from other manufacturers.

It's exactly the same with amplifiers. You won't hear anything from all the well-running amplifiers with Class D power amplifiers because they work well.
But that doesn't work with cheap components and not for $50 or $100.

I have already bought 10-year-old industrial switching power supplies that will continue to run for a long time without any problems, including for one of my Class D amplifiers. But they have a different quality, are sometimes completely capped (still no problem for the service life, strange, right?) and run 24/7 at 500 to several thousand watts without any problems for 5-10 years.

Durability is just a question of development and component quality. If you save on it, the technology doesn't matter, because trash remains trash!

 

[dlaloum]

Yet another failed Class D subwoofer plate amp! This latest one was on a system in our mountain house and was purchased new directly from the manufacturer, Anthony Gallo Acoustics in 2014. It was never abused and was sparingly used on a very nice sounding stereo system with passive wall mounted AGA Strada 2 main speakers ($2000 for the pair). The AGA TR3 subwoofer had cost $1000 new 9 years ago, and my KUDOS to AGA as they are still able to support the customer with a replacement plate amp for $210 shipped. I'm looking forward to receiving and installing it so I can get that system fully operational again.

This latest Class D amp failure brings my total of failed subwoofer plate amps up to 4 out of 6 subs. 3 of those 4 failures were Class D subwoofer plate amp failures, and 1 of the 4 failures was a Class AB subwoofer plate amp failure. The remaining 2 subs don't use plate amps, and have had no failures of any kind. In other words every single plate amp active speaker (all were subwoofers) that I own has failed. One even took out its woofer as collateral damage when it died. This latest one lasted the longest at 9 years before failing, and this one is the only one that is still being supported by the OEM. JBL and EV were not able to support providing replacement plate amps for their subs, and I had to adapt alternative generic plate amps from Parts Express to those subs, which required me making sheet metal filler plates in my metal shop to adapt the OEM sub cutouts (holes) to the dimensions of the replacement plate amps - as there is zero standardization in plate amp dimensions.

Upon visual inspection of this latest failed Class D plate amp I can see a few caps that look bad, but there is a lot of brown Glyptol and white RTV on the board securing components and making board level component replacements too cumbersome an exercise. Thankfully the woofer is fine.

What all of these plate amp failures have in common is that they all lived their lives inside a speaker cabinet with poor ventilation and plenty of vibration. This just adds further fuel to my belief that active speakers, subs or mains, are ALL destined to fail in a vastly shorter timeframe than passive speakers. These failures will be the electronics, unless they fail in a manner that also kills the driver. To be sure, I own several sets of passive main speakers that are over 30 years old with no failures.

I am very appreciative that Anthony Gallo Acoustics is able to support providing a replacement plate amp for my 9 year old AGA subwoofer!!! They are very customer focused, unlike JBL and EV who could not support providing replacement plate amps for subs that were quite younger than 9 when they failed. Anthony Gallo Acoustics was acquired late in 2022 by Pulse-Eight.

My Gallo TR1 is still running happily after 12 years - but its built in amp has a decent external heat sink sticking out the rear...