Class D must read papers and publications

[VQR]

Thanks to Amir, recently I have ditched my enjoyable and lovely sounding, but very hot running (especially during summer), Quad feed-forward ‘current dumping’ 909 power amp (still have it though), and am now biamping my Neat Acoustics Notive 1 speakers, using all class D power amp combo:

a) Buckeye 2-ch amp, based on Purifi 1ET400A board (in high gain, driving tweeter and midrange)
b) Audiophonics, Hyped nCore NC502MP 2-ch based amp (driving bass woofers) … pre-amp is Benchmark LA-4, DAC is SMSL Su-9n

According to Dylan from Buckeye, in high gain mode Purify 1ET400A based amp, perfectly matched with the voltage gain of Audiophonics nCore NC502MP based amp … Buckeye + Audiophonics combo really sounds great … he is definitely right

View attachment 283399


literally unlimited clean power per channel (500+ watts) for less than 2.5 Grands

Now you got room to buy a second set of amps to get the neighbors to file noise complaints.

It's neat how much power and efficiency can be had in such a compact form factor. My rack will probably look kinda bare after removing my old AVR that I only use for stereo. I recently bought the same Buckeye 2ch like yours. Initially I had planned on getting an LA90 Discrete, but honestly the Buckeye is a better buy for me given the price, greater power, and excellent specs.

 

[mdunjic]

Now you got room to buy a second set of amps to get the neighbors to file noise complaints.

It's neat how much power and efficiency can be had in such a compact form factor. My rack will probably look kinda bare after removing my old AVR that I only use for stereo. I recently bought the same Buckeye 2ch like yours. Initially I had planned on getting an LA90 Discrete, but honestly the Buckeye is a better buy for me given the price, greater power, and excellent specs.

LoL … indeed … but my listening room is already smallish, even for this insane amount of power available per channel!

I learned that room itself will start distorting the sound, if sound pressure at my listening position (2.5m away from speakers) is pushed beyond my max sound pressure listening level of 85db … so, if I use Crown power amp calculation, even with 10db amp headroom … I would need utilizing max 80w / ch … which is only about 15% of available power reserve I have.

It is becoming complete insanity with these high performance class D modules and I love it !

 

[mdunjic]

Now you got room to buy a second set of amps to get the neighbors to file noise complaints.

It's neat how much power and efficiency can be had in such a compact form factor. My rack will probably look kinda bare after removing my old AVR that I only use for stereo. I recently bought the same Buckeye 2ch like yours. Initially I had planned on getting an LA90 Discrete, but honestly the Buckeye is a better buy for me given the price, greater power, and excellent specs.

Indeed … the very high quality power amplification these days is getting highly commoditized … unless one is snob in terms of look and feel, ‘golden this’, ‘golden that’, and tube pleasant distortion … ultimate high end, highly accurate, sound reproduction is definitely more affordable than ever !

 

[Ra1zel]

LoL … indeed … but my listening room is already smallish, even for this insane amount of power available per channel!

I learned that room itself will start distorting the sound, if sound pressure at my listening position (2.5m away from speakers) is pushed beyond my max sound pressure listening level of 85db … so, if I use Crown power amp calculation, even with 10db amp headroom … I would need utilizing max 80w / ch … which is only about 15% of available power reserve I have.

It is becoming complete insanity with these high performance class D modules and I love it !

if you listen to 85dB average with high dynamic range music you will have peaks of 100+dB which will require much much more power

 

[mdunjic]

if you listen to 85dB average with high dynamic range music you will have peaks of 100+dB which will require much much more power

True … my max spl that I personally can tolerate is 90db before room starts negatively contributing … so here is approximate calculation for something like that … so I think I am more than ok

 

[Sokel]

True … my max spl that I personally can tolerate is 90db before room starts negatively contributing … so here is approximate calculation for something like that … so I think I am more than ok

That's max,not peak.

 

[mdunjic]

That's max,not peak.

That’s max my ears and room can take it … so in my case that’s actually peak

 

[mdunjic]

In my Roon library 11 LU is max dynamic range I encountered

 

[Sokel]

That’s max my ears and room can take it … so in my case that’s actually peak

Take a look between max and peak :

And another one:

For easy viewing:
Purple for Average
Yellow for Max
Red for peak.

There is an interesting thread here about it:

How loud do you like your music?

I'm interested in how loud you enjoy your music. For this purpose I propose A weighted, slow SPL measuring. I'm also proposing a clean, well produced song that is not bass heavy to avoid subjective impressions of low frequencies (Hey Nineteen - Steely Dan). Since music material varies in dB, I...

www.audiosciencereview.com

 

[mdunjic]

Take a look between max and peak :

And another one:

For easy viewing:
Purple for Average
Yellow for Max
Red for peak.

There is an interesting thread here about it:

How loud do you like your music?

I'm interested in how loud you enjoy your music. For this purpose I propose A weighted, slow SPL measuring. I'm also proposing a clean, well produced song that is not bass heavy to avoid subjective impressions of low frequencies (Hey Nineteen - Steely Dan). Since music material varies in dB, I...

www.audiosciencereview.com

Thanks … yes I understand … regardless … I have never measured spl in my listening room beyond 90 db at listening position … with all of the possible dynamic range of files in my music library … that’s why I call it max spl I measured so far, although it’s peak in my case … meaning … my average listening spl is about 60-65 db

 

[Sokel]

Thanks … yes I understand … regardless … I have never measured spl in my listening room beyond 90 db at listening position … with all of the possible dynamic range of files in my music library … that’s why I call it max spl I measured so far, although it’s peak in my case … meaning … my average listening spl is about 60-65 db

What are you measure your SPL with?
Cause if it's not a true SPL meter or calibrated mic with REW you can't know,phones for example don't measure peaks,only max (the ones I know at least).

 

[mdunjic]

What are you measure your SPL with?
Cause if it's not a true SPL meter or calibrated mic with REW you can't know,phones for example don't measure peaks,only max (the ones I know at least).

I am using iPhone app … it’s for sure good enough, although not ultimately precise … imo, that’s in my case mainly irrelevant … bottom line is that with two high quality, extremely well measured and powerful class D amps, like these:

a) https://www.buckeyeamp.com/shop/p/purifi-1et400a-amplifier-2-channel
b) https://www.audiophonics.fr/en/powe...lass-d-stereo-ncore-2x500w-4-ohm-p-15016.html

which I am using for bi-amping my current speakers, I will probably never hit clipping level, with my listening habits and in my room.

Thanks for the pov btw, highly appreciated

 

[Ra1zel]

I am using iPhone app … it’s for sure good enough, although not ultimately precise … imo, that’s in my case mainly irrelevant … bottom line is that with two high quality, extremely well measured and powerful class D amps, like these:

a) https://www.buckeyeamp.com/shop/p/purifi-1et400a-amplifier-2-channel
b) https://www.audiophonics.fr/en/powe...lass-d-stereo-ncore-2x500w-4-ohm-p-15016.html

which I am using for bi-amping my current speakers, I will probably never hit clipping level, with my listening habits and in my room.

Thanks for the pov btw, highly appreciated

Yeah you are fine for sure I'm just on personal campain to inform people that they are most certainly using more power (on peaks) than they think they do

 

[mdunjic]

Yeah you are fine for sure I'm just on personal campain to inform people that they are most certainly using more power (on peaks) than they think they do

Agree

 

[brightsparkey]

I would like to open the thread dealing with important publications on class D amplifiers principles, topologies, characteristics and limitations. One of the great sources is the Hypex publications library at

Hypex support downloads

Hypex downloads is the place where we publish our application notes and white papers.

www.hypex.nl

The most explaining and resourceful publication is IMHO the "AES Class D master class" presentation

https://www.hypex.nl/img/upload/doc/an_wp/WP_AES124BP_A_universal_grammar%20of%20class_D.pdf

which explains in detail class D principles and also the main different basic topologies, the hysteresis modulator and the phase shift controlled oscillator. Benefits and limitations of both approaches are explained and it would explain to the reader what he could expect from both approaches.

UcD principle and comparison to hysteresis modulator is also explained in

https://www.hypex.nl/img/upload/doc/an_wp/WP_AES118BP_Simple_self-oscillating_class%20D_amplifier.pdf

and NCore improvement over UcD in

https://www.hypex.nl/img/upload/doc/an_wp/WP_Globally_modulated_self-oscillating_amplifier.pdf

and also in

https://www.hypex.nl/img/upload/doc/an_wp/WP_Ncore_Technology.pdf

I believe that these publications might help the ASR visitors for better understanding of results of class D reviews here at ASR.

I would be very grateful if @amirm , @BDWoody or @AdamG247 could make this thread sticky, as it links to basic and necessary literature to understanding of class D function and parameters.
----------------------------------------
https://www.cornestech.co.jp/images/uploads/file/products/pdf/oa_product7-4_201503.pdf
Audio Precision white paper "Measuring Switch-mode Power Amplifiers". All the basic measuring methods like THD, THD+N/level, THD+N/frequency, IMD, DIM, noise, damping factor, crosstalk are explained quite in detail. A lot of permanently repeated questions is answered.

Such a nice looking thread, but - oh no! the links are all bust

Edit: the docs appear to have been moved here:

Hypex support downloads

Hypex downloads is the place where we publish our application notes and white papers.

www.hypex.nl

 

[kevinh]

I had this on my feed today, nice intro to how class D works info from IR and TI.

 

[renzoe]

I would like to open the thread dealing with important publications on class D amplifiers principles, topologies, characteristics and limitations. One of the great sources is the Hypex publications library at

Hypex support downloads

Hypex downloads is the place where we publish our application notes and white papers.

www.hypex.nl

The most explaining and resourceful publication is IMHO the "AES Class D master class" presentation

https://www.hypex.nl/img/upload/doc/an_wp/WP_AES124BP_A_universal_grammar%20of%20class_D.pdf

which explains in detail class D principles and also the main different basic topologies, the hysteresis modulator and the phase shift controlled oscillator. Benefits and limitations of both approaches are explained and it would explain to the reader what he could expect from both approaches.

UcD principle and comparison to hysteresis modulator is also explained in

https://www.hypex.nl/img/upload/doc/an_wp/WP_AES118BP_Simple_self-oscillating_class%20D_amplifier.pdf

and NCore improvement over UcD in

https://www.hypex.nl/img/upload/doc/an_wp/WP_Globally_modulated_self-oscillating_amplifier.pdf

and also in

https://www.hypex.nl/img/upload/doc/an_wp/WP_Ncore_Technology.pdf

I believe that these publications might help the ASR visitors for better understanding of results of class D reviews here at ASR.

I would be very grateful if @amirm , @BDWoody or @AdamG247 could make this thread sticky, as it links to basic and necessary literature to understanding of class D function and parameters.
----------------------------------------
https://www.cornestech.co.jp/images/uploads/file/products/pdf/oa_product7-4_201503.pdf
Audio Precision white paper "Measuring Switch-mode Power Amplifiers". All the basic measuring methods like THD, THD+N/level, THD+N/frequency, IMD, DIM, noise, damping factor, crosstalk are explained quite in detail. A lot of permanently repeated questions is answered.

HI All!! Great post!

(I think this is my frist post, but I've been lurking on the forum for at least one year).

I am a newbie on audio (but Informatics engineering as background).
I am trying to learn more about everyhthing, but now I am down on amplifiers (I am recent owner of a pair of Focal Aria 948, paired with a Denon AVC-X3800H -- also have a central and two surrounds--. I want to improve my stereo experience right now).

Anyway, these links from Hypex seems golden (2021), however they are all offline. My question is:

Does anyone have a copy of them?
( EDIT: OK, I found a page from hypex where at least the first file is hosted. https://www.hypex.nl/support/downloads/ )


I found the first one https://www.diyclassd.com/media/fe/01/90/1682341944/A universal grammar of class D.pdf (Working as 30/11/2023) Put it as attachment.


Regards!

Renzo

 

[kevinh]

Here is a you tube vid on assembling the latest Hypex amp kit.

 

[richardm]

This app note (pdf) from ON Semi was originally published by Motorola some time before 1992. It gives an interesting synopsis of class-D and the issues present at the time.

Strangely it's been through multiple revisions and as best I can tell nothing has changed other than the document footer.

 

[Vhond]

One of the earlier developers of class D: Mueta self oscillating Class D amp