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Why did Class H amps never really catch on?

tvrgeek

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Seems like they're a general improvement over traditional single-rail Class AB as well as Class G in terms of both efficiency and performance, but they never really seem to have caught on for whatever reason outside of some live sound sub applications. Any reason they seem to be less-than-common outside of the AHB2 and some BASH plate amps beyond "well Class D exists and is good enough"?
Don't tell NAD.
Actually there are still quite a few out there.
 

Chr1

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I realised that, but I think we should be close. A NC502MP based amp can be found for about 800€, so the used price should be as low as 500€.


A NC252MP based amp should be in the target range.

EDIT: in fact, this one was sold for about 400€ https://www.canuckaudiomart.com/details/649669840-vtv-amplifier-hypex-ncore-nc252mp-stereo-amp/
Good to see for sure...

Doubtful that there are any available here in the UK, or Europe at 400 Euros tho unfortunately...
 

mhardy6647

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Well, at least film has higher DR.
oh -- I am pro-film*.



Although I am also lazy, and cheap... so I "do" way more digital photography than film nowadays.

________________
* Kinda pro-vacuum tubes, too. Shh! -- don't tell the guys @ ASR!
a0ebe64e15f85637ad1ad3283db13d31.jpg
 

Hapo

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Well... no one, since it's no longer made.
Some folks do still use film, though -- just as some folks do still use vacuum tubes.

...a lot of people still have horses too...soon enough we will be saying such aboot ICE vehicles...
 

mhardy6647

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Our neighbors have two of 'em (horses, that is) -- and way more ICE vehicles than two. :)
 

Hapo

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...it occurs to me that theaudioguy may be hearing impaired...at least he as a positive view on things...
 

mocenigo

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Good to see for sure...

Doubtful that there are any available here in the UK, or Europe at 400 Euros tho unfortunately...

Well, it took me literally 10 seconds to find it. Clearly, they haven’t flooded the market yet, and you cannot find good 30yo class D amps. So there is a point in the argument I vehemently argued against (a modicum of apology on my side is henceforth warranted). Still, “near state of the art” for 3-400€ old and used is a bit of an exaggeration as well, I think.
 

Hapo

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...I am going to get out of this but 30 years ago there were no good class D amps...

...methinks 30 years from now there will be...

...as noted above I did look at a well regarded D class amp and then didn't buy it...
 

fastfreddy666

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Cirrus Logic CS43131 DAC chip uses it to save energy ;) This is explained on page 32 of the datasheet.


cs43131_cr.png

BTW, the DAC chip headphone amplifier measures pretty good. For example it's used in the Hidzis S8 (1) and Tempotec Sonata HD Pro (2).

(1) https://www.audiosciencereview.com/...dizs-s8-usb-c-headphone-adapter-review.10823/
(2) https://www.audiosciencereview.com/...sonata-hd-pro-review-headphone-adapter.22625/

I quote Amirm from the Hidzis S8 review "Wow, are you seeing what I am seeing? SINAD (distortion+noise relative to our signal) of 114 dB?"
The Sonata has a SINAD of 108 dB. I can't explain the difference because the devices are identical on the inside. But still 108 dB is nothing to sneeze at for a dongle that cost USD $54 on Amazon (including shipping) at the time of the review. The Hidzis S8 cost US $129 at the time of the review and is currently not available on Amazon.

So class H did catch on. The reason is simple. The design decreases power consumption and increases efficiency. This is very useful in devices like this and even more in battery driven audio players and such....
 

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Hapo

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...I am going to get out of this but 30 years ago there were no good class D amps...

...methinks 30 years from now there will be...

...as noted above I did look at a well regarded D class amp and then didn't buy it...

...and then......I did...:rolleyes:

 

DanielT

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ZolaIII

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So we have a repetition again.
Classification goes up to Class G, the H inherits class G characteristics with what ever they added (hybrid). They are DC and less efficient than traditional class D. Class D did conquered the world long time ago (all the small amplifiers in numerous things) for the price and whose never meant to be great. Simplicity of class AB will continue to keep it live probably for ever (ever more so in critical applications).
 

DanielT

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So we have a repetition again.
Classification goes up to Class G, the H inherits class G characteristics with what ever they added (hybrid). They are DC and less efficient than traditional class D. Class D did conquered the world long time ago (all the small amplifiers in numerous things) for the price and whose never meant to be great. Simplicity of class AB will continue to keep it live probably for ever (ever more so in critical applications).
Class D is probably mostly, if you now want to, dare, stick your head in that wasp nest and bring it up, about the audibility regarding distortion in the higher frequencies. Plus something that I see appearing all the time regarding class d, that is, how to measure and interpret the results (broadband regarding measuring equipment).:)
 

Calleberg

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Many people consider this to be one of the best power amp ever made.:)

I have read that many have said. Depends of course on what you compare with, but it was (is) a really good power amp.

Class D, I think.

https://www.hifiengine.com/manual_library/nad/208.shtml

No, that little time bomb (NAD208) is neither Class D or H, so not really relevant for this discussion.

D is a switching amp basically a PWM type deal, can be very efficient, like 95%

G is a rail voltage jumper with two or more fixed rail voltages. Properly implemented it improves greatly on efficiency compared to A/B. Nowhere near D though. Typically efficiency at about 70-75%

H is variable Rail where the rail voltage is tracking input signal. A bit complex considered the relatively small gain in efficency compared to the much simpler G

Both G and H are Class A/B amps with trickstery applied to enhance efficiency.

Class D is very much different but not "Digital". Its still very Analog.

An example of a very good class G implementation is the Hifonics Varipover CarAudio amps of yesteryear Designed by Steve Mantz. Extremely rugged, and well behaved beauties with, because of class G, often a somewhat smaller form factor for similar power compared to the competition. (but there where also some show off products in the line up like the "colossus" which, you guessed it, where not small in any way)
 
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DanielT

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No, that little time bomb (NAD208) is neither Class D or H, so not really relevant for this discussion.

D is a switching amp basically a PWM type deal, can be very efficient, like 95%

G is a rail voltage jumper with two or more fixed rail voltages. Properly implemented it improves greatly on efficiency compared to A/B. Nowhere near D though.

H is variable Rail where the rail voltage is tracking input signal. A bit complex considered the relatively small gain in efficency compared to the much simpler G
Sorry I wrote wrong. I know NAD 208 is not a Class D based amp.

However, I did not know if it is a class H or G but you clarified that now. Thanks for that.:)
 
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ZolaIII

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No, that little time bomb (NAD208) is neither Class D or H, so not really relevant for this discussion.

D is a switching amp basically a PWM type deal, can be very efficient, like 95%

G is a rail voltage jumper with two or more fixed rail voltages. Properly implemented it improves greatly on efficiency compared to A/B. Nowhere near D though.

H is variable Rail where the rail voltage is tracking input signal. A bit complex considered the relatively small gain in efficency compared to the much simpler G
In order for something class D to be 95% efficient it needs to have equally efficient AC/DC switching power supply which al do possible never whose a case with class D amps (you would get 85% efficiency regular standard switching power supply).
Clas G-H got it's usage secured in but not for power amplifier (where it likely will stay in the exotic category) but in small integrated power amplifiers for hedaphones/preamplifiers and such (and not for a high gain but lo gain with high SNR).
For example the QC smartphone SoC's (from 5~6 years back including midrange ones) have one but it's put to be used as class D on default or CS43131's amp.
 
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DanielT

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Clas G-H got it's usage secured in but not for power amplifier (where it likely will stay in the exotic category) but in small integrated power amplifiers for hedaphones/preamplifiers and such (and not for a high gain but lo gain with high SNR).
For example the QC smartphone SoC's (from 5~6 years back including midrange ones) have one but it's put to be used as class D on default or CS43131's amp.
Class G based amplifier.:)

 

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Calleberg

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In order for something class D to be 95% efficient it needs to have equally efficient AC/DC switching power supply which although possible never was a case with class D amps (you would get 85% efficiency regular standard switching power supply).
Maybe, but I had this fresh in Memory and it implies that at least 90+ is very much doable. (but I can agree that the 98% numbers shown is questionable)
https://www.avsforum.com/threads/measuring-amplifiers.1780914/page-67#post-54694904

(took the liberty to edit the above quote for clarification, I hope I got it right :) )
 

ZolaIII

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Maybe, but I had this fresh in Memory and it implies that at least 90+ is very much doable. (but I can agree that the 98% numbers shown is questionable)
https://www.avsforum.com/threads/measuring-amplifiers.1780914/page-67#post-54694904

(took the liberty to edit the above quote for clarification, i hope i got it right :) )
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, maybe one day as we see today such PSU [GaN phone chargers] are getting into consumer electronics and pricing of such getting down) as its a bit of a looney tune to pair an 5$ IC with 500$ PSU.
If you pair it with 85 to 90% efficient one then you get 84~89% efficiency (again over 80% utilisation).
 
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