Technics Class A Biasing

[atiq19]

you could try this website for generic info on cross-over error:

http://www.angelfire.com/ab3/mjramp/pagetwo.html

 

[jkeny]

Thanks atiq19,
This site shows Dynamic crossover distortion well & this is what is eliminated in the biasing scheme you asked about. Seems like a worthwhile improvement to me but Andrew & Bob both seem to criticise it because it's not class A according to Andrew (so what) & it still leaves static crossover distortion according to Cordell.

I'm just trying to get Bob Cordell to say how important this static distortion is in the scheme of things? For instance, I understand that it's not frequency dependent which is a good thing as the ear can easily accommodate itself to some level of distortion which doesn't vary (with frequency, etc).

So is the bias scheme being criticised unfairly? Do we need to operate purely in highly wasteful Class A to eliminate a minor non-issue?

 

[atiq19]

I haven't got holistic knowledge about this static + dynamic cross-over distortion phenomenon and their relations to signal variations. this is the first time I have seen such a distinguished answer from Mr Cordell. Best of my knowledge, this area hasn't been investigated with stringent measurement techniques, so far but I may be wrong.

Anyway have a look at the original site:

http://www.angelfire.com/ab3/mjramp/index.html

I think Mr Renardson is not relying only on flimsy non-switching criteria rather he devised some improved feed-forward error correction technique originated in Quad Current Dumping amps.

The whole issue needs to be revisited, I believe.

Cheers

 

[atiq19]

sorry,

my poor writing skills.

I meant, 'such a distinguished/decisive answer from Mr Cordell on this matter'.

I wouldn't bother about class A, B, AAB etc. Class A is class A. I am a low carbon consultant by trade. I wanted to see some innovative solutions to class A amps whereby efficiency could be improved without much compromising to sonic performance. I thought it has already been done so many years gone passed for Hi-fi R&D.

 

[andy_c]

The whole issue needs to be revisited, I believe.

Hi atiq,

I have the AES preprint article on this topology by Danyuk and Renardson. I can email it to you if you wish. I have only glanced at it and not read it in detail.

 

[atiq19]

yes please.

cheers

 

[jkeny]

Thanks atiq,
I'm reading the Renardson site as I post - very interesting - any others built this circuit yet, I wonder? Are you tempted to purchase some pcbs?

 

[atiq19]

I dropped a line to Renardson.

Waiting for response.

 

[atiq19]

Jkeny,

I believe this man has done some some work on Renardson amp:

http://petrh.org/web/renardson.aspx

Mind you this was based on early days design from Renardson. He has refined his toplology to date.

You need google translator to read (?) this page written in Czech.

Also look here:

http://www.diyaudio.com/forums/showthread.php?threadid=30819

cheers.

 

[andy_c]

yes please.

You have mail .

 

[atiq19]

I can't remember now but I have seen some measurements done on non-switching class-B amp by someone. I will post it if I can find the article.

Basically, measurement shows clear improvements(less spikes etc.) under reactive load connected to the modified class-B amps.

later..

 

[atiq19]

Andy,

I got your mail.

Have you got this ?:

Class B in a new class, Mike J Renardson, Apr, 1998, p274,Electronics World.


Many thanks.


Atiq

 

[andy_c]

Have you got this ?:

Class B in a new class, Mike J Renardson, Apr, 1998, p274,Electronics World.

Sorry, I don't have that one. I do have all AES articles through 2003 and some 2004, so keep that in mind if you're looking for AES articles in the future .

 

[jkeny]

ATiq,
I'm sure I can get this in college as they have all electronics world back to the early 90's AFAIK. I will check out it when I'm in there in the next week or so - just remind me by posting here if you don't hear back from me in a week.

 

[atiq19]

jekeny,

thanks for your enthusiasm.

u can include Ian Hegglun in your list.

http://pagesperso-orange.fr/francis.audio2/AmpHegglun.doc

but his principle works best for MOSFETs.

Atiq

 

[atiq19]

food for thought

jkeny,

here is another one from our forum friend Anli:

http://www.diyaudio.com/forums/showthread.php?postid=1704560#post1704560

Atiq

 

[stinius]

Maybe OS could make an AES folder on his site, so we could upload and share the AES papers? I don’t know if it’s allowed, but I have a few that I can upload.
Anybody interested?
It will of course depend on OS.

Stinius

 

[atiq19]

I'm interested.

 

[atiq19]

For Mr Cordell's explanation on limitations of so called non-switching class-B, refer to this thread (post 16)

http://www.diyaudio.com/forums/showthread.php?s=&postid=1708077#post1708077

 

[jkeny]

atiq,
Thanks for the links - I see you're keen on investigating this topology. Like you I also intend to use a Tube preamp, in my case a John Swenson BDT preamp and I will be trying out various output stages including Steve Dunlap's Krill, Susan Parker's Zeus, a Baby Huey tube based amp & possibly Gary Pimm's Solid state pentode (SSP) - (if I have big enough heatsinks)

I see you discovered Swenson's/Pimms voltage regulators - have you used them yet? Are you building them on boards? I'm also using these for the BDT & will be needed for the GP SSP. I have some nice boards - if you need a layout, pm me