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Class D amp long term reliability

When I built my Pontiac 400 (built to 406, for you metric folks 6.7 Liters) that made 473 HP (and got 21.7 MPG (HWY, at 85 MPH [18 MPG @ 55 MPH, 18 MPG @ 110 MPH] in the early 80's, when I ported my heads, I also deburred ALL of the block, heads & chamfered ALL of the oil holes. Deburring a heat sink (for me at least), is just a rainy afternoon project.
It's boring but you just have to keep thinking that it will make life easier in the long run.
As to that engine, the car was stolen without the engine or transmission in it. So I still have them: Doug Nash 5 spd with 4.03 first & 1 to 1 5th.
And now I have a 455 (metric 7.4 Liters) engine to work with.
In a year or so, I'll start looking for a couple chassis/bodys to put them in.
Go hard or go home! YeaH!... LoL.
 
When I built my Pontiac 400 (built to 406, for you metric folks 6.7 Liters) that made 473 HP (and got 21.7 MPG (HWY, at 85 MPH [18 MPG @ 55 MPH, 18 MPG @ 110 MPH] in the early 80's, when I ported my heads, I also deburred ALL of the block, heads & chamfered ALL of the oil holes. Deburring a heat sink (for me at least), is just a rainy afternoon project.
It's boring but you just have to keep thinking that it will make life easier in the long run.
As to that engine, the car was stolen without the engine or transmission in it. So I still have them: Doug Nash 5 spd with 4.03 first & 1 to 1 5th.
And now I have a 455 (metric 7.4 Liters) engine to work with.
In a year or so, I'll start looking for a couple chassis/bodys to put them in.
My restoration project is a 1973 GMC Motorhome, which has an Olds Toronado drivetrain. Also a 455, but an Olds engine, not the big-block Pontiac. Very strong motors--high-nickel blocks, forged or nodular iron cranks, etc. Turbohypertraumatic (spelling?) 425 transmission with a chain drive to turn the drive around for front wheel drive--basically a backwards running Turbo 400 with a chain drive between the bell housing and the input shaft, so that the transmission case runs alongside the driver side of the motor. The final drive is a 3.21 from a Cadillac Eldorado with robust planetary gears, about even with the front of the engine. Wonderful engineering on those things, especially for a motorhome, but the paint now resembles school chalk. Painting a 23' motorhome is a little beyond Earl Scheib.

I will put a Class D amp in the motorhome in the hopes that it doesn't get to hot for reliability (obligatory return to on-topic), and for use only while camping. I have a couple of micro-sized Dahlquist three-way speakers to go with it.

Rick "probably going to have to paint it myself" Denney
 
My restoration project is a 1973 GMC Motorhome, which has an Olds Toronado drivetrain. Also a 455, but an Olds engine, not the big-block Pontiac. Very strong motors--high-nickel blocks, forged or nodular iron cranks, etc. Turbohypertraumatic (spelling?) 425 transmission with a chain drive to turn the drive around for front wheel drive--basically a backwards running Turbo 400 with a chain drive between the bell housing and the input shaft, so that the transmission case runs alongside the driver side of the motor. The final drive is a 3.21 from a Cadillac Eldorado with robust planetary gears, about even with the front of the engine. Wonderful engineering on those things, especially for a motorhome, but the paint now resembles school chalk. Painting a 23' motorhome is a little beyond Earl Scheib.
I will put a Class D amp in the motorhome in the hopes that it doesn't get to hot for reliability (obligatory return to on-topic), and for use only while camping. I have a couple of micro-sized Dahlquist three-way speakers to go with it.

Rick "probably going to have to paint it myself" Denney
I love those motorhomes. The Turbo-Hydramatic 400/425 series of transmissions are among the best in the world. GM sold them to other manufacturers as their OEM transmissions, the were used by Ferrari, Jaguar, Bentley, Rolls Royce and possibly some others. See this under 10 minute video on them (it mentions the GM Motorhome & also says something about that motor homes rear suspension (and talks a but about the very best version of this trans with the switch pitch torque converter:
Back to main topic: Now, about those Dahlquist speakers? Please PM me the model #.
 
...What a mess they were, and it was just not possible to remove the smoky stink from them.
@egellings could have been talking about motorhomes...
My restoration project is a 1973 GMC Motorhome, which has a...
Rick "probably going to have to paint it myself" Denney
Rick "shoulda 1st done a smoke&mold sniff test" Denney?
 
I have to marvel at the tenacity of tobacco smoke stink. It's nearly impossible to remove.
I found a long soft paintbrush with isopropyl or methyl hydrate scrub and then rinse cleans out most of that stuff. I also use ammonia for a scrub down too and that melts the stuff pretty good too. The ammonia or isopropyl sometimes will remove the plastic wax used from then factory and a plastics wax may need to be reapplied if it is something snazzy and nice and it is desired to be slippery feeling and shiny.
 
I found a long soft paintbrush with isopropyl or methyl hydrate scrub and then rinse cleans out most of that stuff. I also use ammonia for a scrub down too and that melts the stuff pretty good too. The ammonia or isopropyl sometimes will remove the plastic wax used from then factory and a plastics wax may need to be reapplied if it is something snazzy and nice and it is desired to be slippery feeling and shiny.
An ozone generator sorta works okay, too. But it’s better with animal smells and mildew.

Rick “nose-blind” Denney
 
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I found a long soft paintbrush with isopropyl or methyl hydrate scrub and then rinse cleans out most of that stuff. I also use ammonia for a scrub down too and that melts the stuff pretty good too. The ammonia or isopropyl sometimes will remove the plastic wax used from then factory and a plastics wax may need to be reapplied if it is something snazzy and nice and it is desired to be slippery feeling and shiny.
PSA: These chemicals are NOT to be used by smokers, for cleaning their lungs of smoking stink and residue.
 
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PSA: These chemicals are NOT to be used by smokers, for cleaning their lungs of smoking stink and residue.
I have one of the hospital machines that do high Powered UV & OZONE. It has a remote control to turn it on. (it has a 30 second delay to let you get out of the room before it actually comes on& off with & some funky colored glasses to have on in case you can't get out of the room in 30 seconds). I always let the ozone level get down before opening the door again. We have this device because we were owners of a therapeutic massage place that Dr.'s in Guam sent their patients to during the pandemic years.
YEP, using high powered UV for cleaning the outside of you & high levels of ozone to clean your lungs would be serious bad news for your health. But, you would likely be microbe free in your body & lungs. The known side effects would be rather harsh though.
 
Back to main topic: Now, about those Dahlquist speakers? Please PM me the model #.
ALS-3. These were the little micro-speakers from 1979 or so. Three-way with a high-parts-count crossover, and they sound pretty good considering their tiny size. Those should work well enough in the application.

I have a cheapie SMSL amp that I might also use, though I'm not terribly impressed with it. But I own it, so I might as well use it. It's a good reliability test--not much control over power quality, temperature, or humidity.

Rick "might be of more general interest" Denney
 
Thank you. I am unfamiliar with that model. But, I have liked the DQ's that I have heard & they have measured well by people "back in the day". I'll se what I can dig up between now & February. (Both time & money are an issue for me until then).
 
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.
 
Plate amps in general have a reputation for bad reliability. I have to guess they are built to a lower price point than conventional stand-alone amps.
 
Plate amps in general have a reputation for bad reliability. I have to guess they are built to a lower price point than conventional stand-alone amps.
Heat sinks on them seem to look a bit small on the non-switch-mode (class AB) ones.
 
Plate amps in general have a reputation for bad reliability. I have to guess they are built to a lower price point than conventional stand-alone amps.
Yes, this I have learned. However, I have also had a small 5 year old ICEpower 50ASX2 Class D amplifier module in a nicely ventilated chassis fail as well - out of the blue with no sign of stress. It just wouldn't turn on one day, just like the plate amps. It was never abused.
 
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. 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. Only one active speaker OEM in my experience actually planned for this eventuality, and I was able to buy a replacement plate amp from that OEM.
 
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. 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. Only one active speaker OEM in my experience actually planned for this eventuality, and I was able to buy a replacement plate amp from that OEM.
One reason I've preferred external amps on my diy subs. If I did build an active speaker, I'd use external amps too. I'm not sold on the reliability of the amps many speaker/sub manufacturers choose...
 
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).
 
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