Why did Class H amps never really catch on?

[Calleberg]

Well if you pair the class D IC with very high grade PSU (best server grade ones have efficiency of 97% when pushed hard 80+%) you can land with 95~96% (again when pushed hard over 80%) efficiency but no one will do that (at least not yet...

WUT? what are you on about? It appears Peavey did just that! And I think the Ipr2/Pro lite amp line started selling in 2014...
Those measurements I linked are of an actual product that does exist...

 

[killdozzer]

I read this whole thread hoping someone would mention Class E, since we're talking about Class D and perhaps give some interesting perspective. Like is it of any use for the new generation of Class D?

 

[ZolaIII]

@Calleberg I think you do know basic math and believe in physics and if you don't I really can't help you there. Only two Fujitsu server SPSU ever to mu better knowledge reached 97% efficiency (usually they are over 90 92~93%).

 

[Chr1]

Picked up one of these in mint condition for £100 a couple of years ago. Haven't actually used it as yet. It is built like a tank.

Perfect subwoofer amp, I reckon.

LD Systems LDPA1600X

View attachment 178299

Back to Class H...

The reason I reckon that this amp that I bought would be great for a pair of subs is that when I bought it I remember, after a bit of research, reading online that something to do with the Class H topology means that there can be issues with distortion at the higher frequencies. Can't remember the reason but perhaps someone more knowledgeable can chime in?...

Anyhoo, perhaps this is the reason why Class H never really caught on for hifi use.

 

[Calleberg]

@Calleberg I think you do know basic math and believe in physics and if you don't I really can't help you there. Only two Fujitsu server SPSU ever to mu better knowledge reached 97% efficiency (usually they are over 90 92~93%).

Aswer these two questions.

#1What product is measured in the link?
#2What is the Measured efficiency in that Link?

Hint, it is NOT a server, and no need to apply any real mathematics just read the numbers.

https://www.avsforum.com/threads/measuring-amplifiers.1780914/page-67#post-54694904

 

[ZolaIII]

Aswer these two questions.

#1What product is measured in the link?
#2What is the Measured efficiency in that Link?

Hint, it is NOT a server, and no need to apply any real mathematics just read the numbers.

Sorry I won't even comment on that until you tell me what is used for all of the measurements there. As much as I did see it's dummy output loads based and the 2ch driven into 2.2r measurements are in line with 90+ efficiency SPSU (driven above 95% of their maximum output) and price of such is easier to justify when we speak about 4 KW stage amplifier.
For putting it into write perspective efficiency is more important in large power consumers and servers are huge one's and price is a less of an issue in that particular segment. Fujitsu has 2.5x more efficient servers (ARM V8.2 with SVE) than current X64 contraparts (AMD). It's much less important for your home 100W power amplifier which you will use between 1 to 10W most of the time.

 

[Calleberg]

Back to Class H...

The reason I reckon that this amp that I bought would be great for a pair of subs is that when I bought it I remember, after a bit of research, reading online that something to do with the Class H topology means that there can be issues with distortion at the higher frequencies. Can't remember the reason but perhaps someone more knowledgeable can chime in?...

Anyhoo, perhaps this is the reason why Class H never really caught on for hifi use.

Nah, the real reason is probably, for domestic hifi use atleast, that the gain in efficency did not bring any added value to the table for the average audiofool. And the added complexity was probably discouraging on top of adding additional cost.
The advantages of Class G however did and was less complex and actually cheaper than a similar Traditional A/B amp running constantly on the high voltage rails and therefore was considered "good enough".

 

[Calleberg]

Sorry I won't even comment on that until you tell me what is used for all of the measurements there. As much as I did see it's dummy output loads based and the 2ch driven into 2.2r measurements are in line with 90+ efficiency SPSU (driven above 95% of their maximum output) and price of such is easier to justify when we speak about 4 KW stage amplifier.
For putting it into write perspective efficiency is more important in large power consumers and servers are huge one's and price is a less of an issue in that particular segment. Fujitsu has 2.5x more efficient servers (ARM V8.2 with SVE) than current X64 contraparts (AMD). It's much less important for your home 100W power amplifier which you will use between 1 to 10W most of the time.

I see the goalposts are now starting to move around as I expected they would...

Anyway no need to spam the thread anymore with this mostly irrelevant old mans quarrel.
I think most people in here can read the numbers just fine in that link...
I´ll leave it at that.

 

[ZolaIII]

https://imgur.com/BJaAB0C

Realistic would only be the hotest signal area where it would need most gain and that brings you down to 85%. I hope you understand now.

 

[DanielT]

Who cares about different amplifier classes, really? Certainly in this thread, from a theoretical perspective, and I think that is also interesting! But purely practical for home hi-fi use, most people do not care regarding this with classes, I do not think so in any case. Then it is probably mostly "bang for the buck"(power, plus features, plus if any glossy Hifi magazine raises the amplifier to the skies) that applies. And brand,reliability and durability.

Perhaps regarding class D that there is still a presumption that it is only suitable to subwoofer amplification, but even where the large home- Hifi buying mass of buyers I think ignores that. Thus, the manufacturers create what gives the "bang for the" buck for them. It seems to be class D these days.

Note, I wrote the presumption regarding class D.

 

[ZolaIII]

I care about great (and even good designs) disregarding of class and typology and it's a great thing if I can upkeep them.
Let's play wintage.

Hitachi HMA-8500 Mk II Review

That's class AB made to work more like class A.
More importantly take a look at it's predecessor's in History labeled part where you will see 1977 class G one's (as that is not that new) as we nead to put an end to the classification nonsense.

 

[DanielT]

I care about great (and even good designs) disregarding of class and typology and it's a great thing if I can upkeep them.
Let's play wintage.

Hitachi HMA-8500 Mk II Review

That's class AB made to work more like class A.
More importantly take a look at it's predecessor's in History labeled part where you will see 1977 class G one's (as that is not that new) as we nead to put an end to the classification nonsense.

Are you absolutely right. May I guess: Most people who are on ASR reason in the same way (me too). Well constructed amplifiers, good quality. Of course that has good performance then class in itself does not matter. Well maybe if you look at it this way, reliable stuff or wear and tear? Time will tell:

Class D amp long term reliability

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...

audiosciencereview.com

The Hitachi HMA-8500 Mk II seems to be a gem.
Get one and fix it. If needed , service and recap and so on. Then you have made a small contribution to the environment. Kept a nice vintage amp alive.

 

[ZolaIII]

Are you absolutely right. May I guess: Most people who are on ASR reason in the same way (me too). Well constructed amplifiers, good quality. Of course that has good performance then class in itself does not matter. Well maybe if you look at it this way, reliable stuff or wear and tear? Time will tell:

Class D amp long term reliability

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...

audiosciencereview.com

The Hitachi HMA-8500 Mkii seems to be a gem.
Vintage, you get one and fix it. If needed so, service, recap and so on. Then you have made a small contribution to the environment. Kept alive a nice vintage amp.

It's a gem (a MOSFET one) but same can be said (even more in relevance to this thread) for HMA-8300 from 1977 (200W class G).

 

[DanielT]

It's a gem (a MOSFET one) but same can be said (even more in relevance to this thread) for HMA-8300 from 1977 (200W class G).

Look at that.

But what do you think about: Damping factor: 50?
I do not really understand that with how much DF is needed (Is not a current powerful amp what you should aim for?) , but other than that. For those who have time and knowledge (service, possible recap) and so on, I do not see why you should buy a new amplifier? Fix an old one instead.

Hitachi HMA-8300 Stereo Power Amplifier Manual | HiFi Engine

www.hifiengine.com

Edit:
Not all countries were trusted to run 4 Ohm speakers with it I see. Strange.

 

[ZolaIII]

@DanielT either ask someone who can easily explain it or read the wiki regarding dumpling factor.
Most people aren't able to service (pretty much anything anymore) and that's why "good" affordable and as new designs are important. If you find any of those Hitachi amplifiers or an old JBL L100's with a great price and in good shape please let me know.

 

[DanielT]

@DanielT either ask someone who can easily explain it or read the wiki regarding dumpling factor.
Most people aren't able to service (pretty much anything anymore) and that's why "good" affordable and as new designs are important. If you find any of those Hitachi amplifiers or an old JBL L100's with a great price and in good shape please let me know.

OT
Yes, I howl if I come across some of those Hitachi amplifiers or JBL L100.
You are probably right about that maybe not so many who have both theoretical knowledge and practical experience in service/fixing. Maybe not have the desire for it either. What do I know.

I know this with DF in general. More whole package interaction speakers- amp I mean. Note I look around the forum. There are some who test different variants, under different conditions and report the results. Fun to learn.

 

[DonH56]

I read this whole thread hoping someone would mention Class E, since we're talking about Class D and perhaps give some interesting perspective. Like is it of any use for the new generation of Class D?
View attachment 179634

Class E uses resonate circuits and is useful at RF, not so much at audio, due to the very low frequencies (requires very large resonator components) and very wide bandwidth (hard to optimize a resonator over so many octaves). Class E amplifiers I have designed and seen are generally narrowband designs, less than an octave, at hundreds or thousands of MHz.

 

[DanielT]

Aha, my subwoofer amplifier is a class H based amplifier.I did not know that.

 

[Calleberg]

Aha, my subwoofer amplifier is a class H based amplifier.I did not know that.

Well it is not but it does highlight the existing confusion of what is to be defined as Class G or Class H.

 

[DanielT]

Well it is not but it does highlight the existing confusion of what is to be defined as Class G or Class H.

Que, it's not Class H? It is Thomann who states it is:

the t.amp E-800

Stereo Amplifier Power: 2x 500 W at 4 Ohm, 2x 350 W at 8 Ohm, 1 x 1000W bridged at 8 Ohm (@ 1 kHz, THD

www.thomann.de

You mean it is Class G?(Not that there's anything wrong with that).