CFA Topology Audio Amplifiers

Jump to Latest
#2,881
Jay said:
First, not everyone use English in his daily life.
Click to expand...

I know, but that wasn't the case here, the statement was like 'I use the word in a different meaning...'so the original meaning was well known.

Jay said:
Third, what is a word. Think about it. Many high end speakers are "detailed", "resolving", but not "accurate". What is accuracy anyway if one only can think of THD as the only measure of accuracy.
Click to expand...

Well sure, that's one of the problems with reviews, isn't it? Reviewers use such words and anybody can attach any meaning to it as he/she likes.
So you get everlasting discussions because someone uses a word for a different meaning than others.

Nobody here would start to talk in Swahili and expect the other guy to know what he's going on about. Yet, changing the meaning of words to suit your own agenda amounts to the same.

Jan
 
#2,883
Jay said:
First, not everyone use English in his daily life.

Second, intelligent people can well read between the lines.

Third, what is a word. Think about it. Many high end speakers are "detailed", "resolving", but not "accurate". What is accuracy anyway if one only can think of THD as the only measure of accuracy. African woman is more similar to Chinese woman than African woman to African man.
Click to expand...

4th...
There are no transparent amp in this world. There are also no TRUE CFA, no CFA in this world.😀 Current sensing with shunt resistor is actually reading its voltage.
 
#2,886
RNMarsh said:
I believe you -- but Like I said what is allowed/shown in schematics from them you cant tell what they did and the circuit description in the manual says differential input with CCS etc. And, it is not direct coupled in the feedback path-- it is at the I/O. Etc. It no doubt sounds great. I think we are doing better today and from what I see here at DIYAudio.. a lot better. Save your 4000E and build one of these here.

Thx-RNMarsh
Click to expand...
Pioneer M-Z1 input stage is nothing more then his famous Pioneer Super Linear Circuit (SLC).

130988d1239140406-aes-e-library-super-linear-circuit-ozawa-okio-ishikawa-kikuo-pioneer-cz-1-sch.jpg


PIONEER A-09 also has very interesting CFA input stage
A-09_inputstage.JPG
 

Attachments

#2,887
manso said:
While this is true, it in fact was pioneer that pioneered the diamond input stage for CFAs. This was long before Comlinear, it took 3 years for pioneer to have their patents granted in the USA, one has to wonder why, when Comlinear patents were granted within months. Pioneer patents were rejected due to technicalities and they had to file revised version before they were granted. I have copies of both Pioneer and Comlinear patents and there is nothing wrong with the first Pioneer patent that was requested. Comlinear patents should never have been granted in the first place as they clearly infringe on Pioneers patents.
Click to expand...

If that surprises you, the basic CFA circuit was again patented in 1998 (Bender) and basicly the entire IC industry was sued for infringement (I'm not kidding).

IIRC Comlinear had a lot of claims on the biasing schemes, and AFAIK nobody ever paid royalties on IC CFA's to anyone. As Dick pointed out the diamond arrangement was put into the public domain in 1963.
 
#2,888
banat said:
For those interested here is the article from Nov.1954 describing E.V. A20 tube amplifier circuit which use variable damping factor , achieved from variable voltage and current feedback amount insertion on input tube cathode .
Click to expand...

This is not a current feedback topology amplifier. Its still a VFAmplifier. I have done this sort of thing with solid state VFA and it works well to reduce the loudspeaker THD.... the more important aspect to me than damping per se.


Thx-RNMarsh
 
Last edited:
#2,889
Very nice designs for audio amps. Many designers were on the same track back then. Some care must have gone into the tempco of the circuit/build to keep the dc offset from moving too far. Did these amps have any patent numbers printed on their chassis by any chance?
What is in the block diagrams from the output to + and -4v I/V points?

-Thx-RNMarsh



jony said:
Pioneer M-Z1 input stage is nothing more then his famous Pioneer Super Linear Circuit (SLC).

130988d1239140406-aes-e-library-super-linear-circuit-ozawa-okio-ishikawa-kikuo-pioneer-cz-1-sch.jpg


PIONEER A-09 also has very interesting CFA input stage
A-09_inputstage.JPG
Click to expand...
 
Last edited:
#2,893
early CFA -

jony said:
See this patent
Amplifier circuit

DC detection circuit - dc servo
Click to expand...

Nice topology idea. they refer to all the known parts of their circuitry by their pre-existing known names --- Current Mirror, DC servo. etc.
Its another way to put together a new combination of ideas. Diamond buffer, DC Servo, Current Mirrors had been published by that time. But they are good circuits... many other combo circuits exist but they did it for audio asap. Are there any current 🙂 models by them or other companies which has audio patents on similar topologies? Any Accuphase perhaps?


Thx-RNMarsh
 
#2,895
RNMarsh said:
I believe you -- but Like I said what is allowed/shown in schematics from them you cant tell what they did and the circuit description in the manual says differential input with CCS etc. And, it is not direct coupled in the feedback path-- it is at the I/O. Etc. It no doubt sounds great. I think we are doing better today and from what I see here at DIYAudio.. a lot better. Save your 4000E and build one of these here.


Thx-RNMarsh
Click to expand...

No way Richard, Im still after one of those amps, my home amp is a lavardin which is a great amp too but to my ears it loses to these pioneers. The lavardin cost me 3 times the price. I auditioned the pioneer against amps like VTL, Pass and BAT and it was upto the task, except it costs (second hand if you can locate an owner to sell) less than a 1/10 of some of these monsters. Also the pioneer is 30 years old and still using original parts, never touched.

Only the wife prevented me offering more. 🤐
 
#2,896
RNMarsh said:
Possibly.... I think we are all starting to get the picture.
Take a Dynaco PAS2-3 preamp... output fb resistor taken back to the cathode of input tube. CFA? Only if you wish it to be.

Factoid -- the diamond configuration - specifically the diamond buffer was not invented by Panasonic. Though they may have some claim to another diamond variation. The Concept was 'invented' by Baker at MIT in 1963 and published in IEEE papers.... so Panasonic or anyone could use it. Variations et al is the area of patents. My variation/contribution was to take the CFA or compound complimentary push-pull circuit and configure it into a DC/Direct-Coupled configuration and later added ['invented'] the concept of a dc servo. My 5 minutes in the sun. There are many DC variations and many servo variations.... many are better than the original.

Lets get back to the solid state, modern CFA topology and description.

Contrary -- that CFA are harder to compensate?.... they have been shown in my experience to be easier when adding in the HF low distortion at the same time. Can this be elaborated on for everyone's benefit?


Thx-RNMarsh
Click to expand...

The diamond buffer was not invented by Pioneer, its use as the input of CFAs was. Before them no one had included either a TIS or current mirror and used it for voltage amplification. Thats why there was so much secrecy about it.
 
#2,897
scott wurcer said:
If that surprises you, the basic CFA circuit was again patented in 1998 (Bender) and basicly the entire IC industry was sued for infringement (I'm not kidding).

IIRC Comlinear had a lot of claims on the biasing schemes, and AFAIK nobody ever paid royalties on IC CFA's to anyone. As Dick pointed out the diamond arrangement was put into the public domain in 1963.
Click to expand...

I see this a lot, there are many amp manufacturers infringing on each others patents whithout one knowing about the other. I guess thats the reason schematics are not so easily released.😀
 
#2,898
manso said:
No way Richard, Im still after one of those amps, my home amp is a lavardin which is a great amp too but to my ears it loses to these pioneers. The lavardin cost me 3 times the price. I auditioned the pioneer against amps like VTL, Pass and BAT and it was upto the task, except it costs (second hand if you can locate an owner to sell) less than a 1/10 of some of these monsters. Also the pioneer is 30 years old and still using original parts, never touched.

Only the wife prevented me offering more. 🤐
Click to expand...

OK. Seems many companies - not just small 'audiophile' types have gone away from strictly VFA/differential input/VAS/OPS - the blameless configuration - and its been that way for years now. But, I think some of the designs seen here and elsewhere with great semiconductors; fets and MOSFETs, better passive parts et al are up to the task with benefit of advanced SIM PC/sw.


Thx-RNMarsh
 
Last edited:
#2,899
jan.didden said:
I know, but that wasn't the case here, the statement was like 'I use the word in a different meaning...'so the original meaning was well known.
Click to expand...
And that IS you assumption. There is nothing wrong with making assumption. Problem is when you assume that your assumption is always right.

jan.didden said:
Nobody here would start to talk in Swahili and expect the other guy to know what he's going on about. Yet, changing the meaning of words to suit your own agenda amounts to the same.
Click to expand...

I can go to Swahili people to find out what is the best amp there. My point is: language is NOT the one that creates deadlock.

Why you assume there is "agenda" everywhere?
 
You must log in or register to reply here.
Top Bottom