What are the reasons to choose Class A/AB/H over D in this day and age?

[jhaider]

Nah, the 80s and 90s cars I bought new lasted for 300K miles with little effort!

I note that “little effort” here is undefined.

Here are a few emissions based problems:

That’s cute. None of those things exist on modern cars. But basically what I read below is you’re bemoaning the fact that the expectation is emissions mitigation equipment is now expected to work properly, and designs have been improved such that the user is notified when it does not. Before a car could run with this equipment in poor repair and none would be the wiser.

And yes, evaporative emissions of liquified prehistoric toxic dead algae corpse fumes is a problem. People should have learned how to use their caps properly.

 

[antennaguru]

Getting back on topic:

What are the reasons to choose Class A/AB/H over D in this day and age?​

I'm going to say that objectively BOTH short and long term reliability! In my experience using Class D plate amps and Class D modules over the past 5 years or so, I have already experienced a 50% short term failure rate, defined by ~5 years. We'll have to see about the longer term failure rate, but I fully expect 100% to have failed by 10 - 15 years.

Meanwhile, I have built and bought a vast number of Class AB and Class A amplifiers, both solid state and tube, and never experienced anywhere near this high a failure rate. In no case was I unable to repair the Class AB or Class A amplifier.

In my conclusion, anyone interested in amplifier longevity should run, not walk, away from expensive Class D amplification until there is solid proof of ongoing reliability. We saw the pictures of a blown Hypex, and then there was also the other Hypex that the assembler stepped in and replaced under warranty.

On a happier note for Class D modules available at a reasonable cost, the 3 out of 6 Class D amplifiers I have that have not yet failed are all IcePower 125ASX2 module based. Two of those three I built with Class A input stages.

I cannot personally speak to the more expensive Hypex or Purifi module reliability as I would not invest in their quite higher module cost until they can at least prove their short term reliability. I don't care where they stack rank in SINAD as the difference in audibility just isn't there for me - at least with the Hypex and Purifi units I have heard.

On the subjective front, I recently heard a customer's very nice system with a Class A amp, and we compared it to a Hypex Ncore module amp he had been loaned, and one of my IcePower 125ASX2 amps, and we all felt that the two Class D amps lacked soundstage depth compared to the Class A amp - but there is no way to measure soundstage depth on test equipment like an AP, and stack rank that way. The only way I know to compare soundstage depth is by playing and subjectively listening to known recordings that exhibit good soundstage depth. Those that have never heard good soundstage depth probably don't care anyway - because we don't know a way to measure it with test equipment.

In any case, Merry Christmas to all that celebrate, and Happy Holidays to all.

 

[Holmz]

Getting back on topic:

… - but there is no way to measure soundstage depth on test equipment like an AP, and stack rank that way. The only way I know to compare soundstage depth is by playing and subjectively listening to known recordings that exhibit good soundstage depth. Those that have never heard good soundstage depth probably don't care anyway - because we don't know a way to measure it with test equipment.​

In any case, Merry Christmas to all that celebrate, and Happy Holidays to all.

Well Santa measures depth by the intensity of the glow from the nose of Rudolf.
This all goes to $hit in Australia, so he swaps out the reindeer with 6 big old man kangaroos, call the six white boomers.

 

[watchnerd]

After a decade of Class D (IcePower) and A/D hybrid amps, I've gone back to Class A-biased/B.

It's big and hot and I like that.

And the VU meters.

And the smell.

 

[DimitryZ]

Nah, the 80s and 90s cars I bought new lasted for 300K miles with little effort! After 2000 the emissions sensors have been driving me and a lot of other people crazy - that are trying to get 300K miles out of their vehicle, which is truly the best thing for the environment. Here are a few emissions based problems:

1. Loose gas cap that my wife put on causes a "Check Engine" light on all of our cars - because the purpose of the gas tank pressure sensor is to reduce hydrocarbon evaporation out of the gas cap as a part of the overall emissions requirements of the EPA. You need an OBD2 reader to turn off the code (and the "Check Engine" light) once you clean and tightly put the cap back on. How much gas cap emission could that possibly save? If you don't have your own OBD2 reader it will cost you a few hundred dollars at the dealership in diagnostics and a new cap and/or sensor.

2. ECO mode using VCM (Variable Cylinder Mgt) to reduce emissions and save gas by turning off cylinders - which it doesn't save jack if you live in a hilly area (probably does help a little if you live in the flatlands where you can see the curvature of the Earth). There are sensors on each bank of the engine that go bad and cause a "Check Engine" light. It's so widespread that an aftermarket VCM-Muzzler is widely sold to stop the VCM from engaging altogether. Another stupid idea driven by an emissions requirement. I just ordered the VCM-Muzzler after biting the bullet for $400 at the dealership for the sensor replacement. When the "Check Engine" light is on and ECO won't engage I do get a 1 mpg improvement - BUT can't turn off the VSA/VSC electronic yaw control which I do need to do turn off to make it up hills in snowy weather. Pulling the VSA fuses will also disables the ABS which I do want, so that dog won't hunt...

3. You get a "Check Engine" light for low catalytic converter efficiency. I have that situation now on one car and turn it off with my OBD2 reader every 1500 or so miles, and specifically right before I take it in for annual inspection. I'll drive it until the catalytic converter falls off and then replace it for the requisite $1000 because you can't clear the code if you put a bypass pipe thru the middle of the old cat.

4. Bad O2 sensors cause a "Check Engine" light, and again cost $$$ to get replaced. They are usually a couple of them in there to control engine timing, etc. in order to reduce emissions. They go bad.

Shall I go on?

My cars in the 80s and 90s broke all the time.

My cars today almost never break.

I definitely don't miss being under the car with a wrench.

300k miles in northern latitudes is not possible without a garage, unless you drive crazy number of miles a year. The car simply rusts away.

 

[Timcognito]

In California our population has grown by 30% and yet Ozone most unhealthy air pollutant has gone down by 50% since 1980. Can't wait until we have every one driving electric cars. The problems encountered above have to do with internal combustion engines, an over dependence on fossil fuel, lack of mass transit and at same time wanting to reduce cancer and lung disease and have clean air. I agree with those who say cars are better now.

I thought this discussion was about amplifier technology.

 

[Holmz]

In California our population has grown by 30% and yet Ozone most unhealthy air pollutant has gone down by 50% since 1980. Can't wait until we have every one driving electric cars. The problems encountered above have to do with internal combustion engines, an over dependence on fossil fuel, lack of mass transit and at same time wanting to reduce cancer and lung disease and have clean air. I agree with those who say cars are better now.

I thought this discussion was about amplifier technology.

It was about amps, but since no one seemed to be able to present an audio case for it, the discussion turned to global warming as a reason for Class-D... as well as landfills.

 

[watchnerd]

As an aside, I've decided most audio reviewers must be weaklings given how they talk about how heavy Class A amps are.

Several of the reviews of the Luxman L-590AXII I read talked about needing to get help from a friend to unbox the amp, lift it into the rack / shelf, etc.

I was prepared for a behemoth, but I had no such issues, did everything solo -- then I checked the weight, and it's only 28 kg / 61 lbs.

My dear departed dog weighed more than that.

 

[SIY]

My dear departed dog weighed more than that.

Did you put your dog on the rack/shelf?

I have to plead guilty- in my review of one of the large Parasound amps, I made exactly this complaint. I have been spoiled by "hold it in the palm of an outstretched hand" amps like Purifi.

 

[mhardy6647]

Did you put your dog on the rack/shelf?

I have to plead guilty- in my review of one of the large Parasound amps, I made exactly this complaint. I have been spoiled by "hold it in the palm of an outstretched hand" amps like Purifi.

So... you'd like the Carver Crimson 275 amp, then.




(I'm sorry... I just can't help myself sometimes. As the late Bea Arthur's iconic TV character Maude* would say: "God'll get you for that". )

___________________
* Speaking of dating oneself.

 

[watchnerd]

Did you put your dog on the rack/shelf?

I have to plead guilty- in my review of one of the large Parasound amps, I made exactly this complaint. I have been spoiled by "hold it in the palm of an outstretched hand" amps like Purifi.

When he got too old to jump, I lifted him into the back of my SUV multi times a week, which is higher off the ground.

He weighed 74 lbs in his dotage.

 

[Kal Rubinson]

Deleted.

 

[watchnerd]

Did you put your dog on the rack/shelf?

I have to plead guilty- in my review of one of the large Parasound amps, I made exactly this complaint. I have been spoiled by "hold it in the palm of an outstretched hand" amps like Purifi.

It's so common it's almost a cliche, but I bet the manufacturers love it.

"This Krell / Threshold / Mark Levinson / Pass amp is so heavy" = charge more money

The follow-up comment was usually something about how the wife noticed the difference in sound from the other room.

My wife also commented on the Luxman L-590AXII, saying:

"That one just looks like a big box. The old one [Devialet Expert] looked better."

"It's retro, honey."

"Well now your record player [Michell Gyro SE] doesn't match. It's too futuristic looking"

"Actually, that's a vintage model, the design is very old, it was just futuristic looking at the time."

"Well it still doesn't match your new box. You need to get that square kind of record player with the lid. That would look better."

 

[sq225917]

The answer to the question is ease of serviceability. Class a, b etc use more power but anyone with a clue can fix em. Any other reason is purely down to matters of taste.

 

[DimitryZ]

The answer to the question is ease of serviceability. Class a, b etc use more power but anyone with a clue can fix em. Any other reason is purely down to matters of taste.

You can fix the power supply.

You can't fix SMT boards at home. An SMT repair station (at our PWB factory center, for example) is a big deal, very expensive, and is run by a very experienced operator.

In my A/B Emotiva amps, there is a big SMT board that would need to be replaced if it went bad. And it's much bigger that the entire D amp.

 

[mhardy6647]

FWIW...
I actually know folks (admittedly, pros who dabble in DIYer focused projects) who are doing plenty of... well... DIY with (tiny) surface mount dealies. It requires some vision enhancement tools and the right soldering hardware, but they swear it's even within the capabilities of old presbyoptic guys like... well... me.

I even have the boards for one of one such person's DIY-canted projects (a vacuum tube phono preamp) -- but haven't worked up the gumption to do anything with 'em yet.

 

[MakeMineVinyl]

You can't fix SMT boards at home. An SMT repair station (at our PWB factory center, for example) is a big deal, very expensive, and is run by a very experienced operator.

Sure you can. Buy one of these with some solder paste and do a good deal of practice. Variations on this SMD workstation are used in our factory with excellent results. If there are strict government safety regulations for rework, that's a different thing.

I've hand soldered 0201 size resistors with a microscope and very small tipped soldering iron - it's not a pleasant experience, but it can be done.

 

[DimitryZ]

Sure you can. Buy one of these with some solder paste and do a good deal of practice. Variations on this SMD workstation are used in our factory with excellent results. If there are strict government safety regulations for rework, that's a different thing.

I've hand soldered 0201 size resistors with a microscope and very small tipped soldering iron - it's not a pleasant experience, but it can be done.

The one in our factory is 1000 times more expensive. Has a 3-D X-ray station to check component alignment and joint coverage/quality.

Again, it's a sub hobby in itself. Most equipment owners do not want to do microscopic soldering. And typical SMT designs aren't made for individual component diagnosis - so few or no test points.

 

[pjug]

You don't even need hot air for rework of something like 8 pin or 16 pin SOIC if you are not doing a lot of rework. Just pull up one leg at while heating with an iron to get them off and put the new one one with an iron. I never got the hang of hot air and this is how I do the minimal rework I have to do on those kind of parts. 1206, 0805, 0603 size resistors and caps are so easy that I don't know why anyone would rather deal with through hole.

 

[MakeMineVinyl]

The one in our factory is 1000 times more expensive. Has a 3-D X-ray station to check component alignment and joint coverage/quality.

Again, it's a sub hobby in itself. Most equipment owners do not want to do microscopic soldering. And typical SMT designs aren't made for individual component diagnosis - so few or no test points.

Your facility probably isn't involved in audio component manufacturing. We send all our boards out for SMD stuffing but there are a few operations which have to be done by hand or flow soldered with through-hole parts, leads, power transistors etc.