F6 Amplifier

[Zen Mod]

what you are going to do with the bird ?

keep it in cage ?

as long you can see it , with naked eye or .... , any bird is same good .

point is in looking at it , not having prettiest one

you started to look at one of yours , recently - Compound amps .

[lhquam]

Using a hint from Nelson's "F6 Conceptual Schematic" about V2+ and V2-, I came up with another approach to the bias voltage generation using TL431 voltage regulators in a TO-92 package. This generates both the reduced voltages for the input JFETs and regulated voltages for the bias circuits, making it very insensitive to the V1, V2 rail voltage fluctuations.

[buzzforb]

Originally Posted by lhquam

Using a hint from Nelson's "F6 Conceptual Schematic" about V2+ and V2-, I came up with another approach to the bias voltage generation using TL431 voltage regulators in a TO-92 package. This generates both the reduced voltages for the input JFETs and regulated voltages for the bias circuits, making it very insensitive to the V1, V2 rail voltage fluctuations.

do you get a significant change in performance?

[lhquam]

Originally Posted by buzzforb

do you get a significant change in performance?

The difference is more tolerance to rail voltage variations. No known difference otherwise.

[lhquam]

I decided that it was a bad idea to try to economize on the resistor count by connecting the TL431 REF pin to the bias circuit potentiometer. Here is a revised schematic. This also restores the resistor charging the bias capacitor to somewhere near 10K ohms.

[Antoinel]

Originally Posted by Zen Mod

what you are going to do with the bird ?

keep it in cage ?

as long you can see it , with naked eye or .... , any bird is same good .

point is in looking at it , not having prettiest one

you started to look at one of yours , recently - Compound amps .

ZM. We are into philosophy, and it is all right. I am not telling any DIYer to do anything. You DIYers are the football, soccer and basketball stars on the field, and excell at what you do. I am a fan and an observer cheering and celebrating your achievements. I point connections and possible direction which are still within the bounds of the thread. lhquam has a clear objective to guess the design of Mr. Pass. What if Mr. Pass is operating his F6 in Class A/B? Slim chance in the possible view of many of you; but a possibility nonetheless because it was practiced with the old classic [nothing new] and sounded great.
I hope the comment you made on my thread Compound Power Amps is good. I did not understand it fully. It is a privilige for me to write on diyAudio; just like driving a car in the U.S.A. In all of my threads, I communicate ideas [some are weird], attach them with experiments and results like you, lhquam and others have done and continue to do. My posts are up for grabs by any DIYer to practice, laugh at, ridicule , enjoy etc. I am not selling anything; just passing therapeutic time.

[Zen Mod]

I just forgot to put a smiley ........

[lhquam]

Since my amplifier power needs are happily satisfied with less than 25W, I have no real interest in spending (wasting) time of Class-AB circuits.

Originally Posted by Antoinel

Your circuit is simple, robust and delivers great performance and sound. Mr. Pass may release his schematic in the future. In the interim you and others are telling the world of diyAudio the bigger potential of Teaser-6 and Franken6. Have you cast anything/performance in stone? You and buzzforb, ZM, and others are/have been the source of valuable info; not Mr. Pass. Who is gonna tell/show us how Teaser-6 and Franken6 perform as a Class A/B. Will it be Mr. Pass? I feel priviliged [and hope that others also do ] that you and others are sharing valuable info about your rendition of Conceptual F6. I care about what you, buzzforb and others are doing. I can't care about what Mr. Pass is doing because I know nothing about his activity, and thus why care about a high level secret; albeit valuable? I care about the proverbial bird at hand [Teaser6, Franken6] and not the one on a distant tree [F6 by Mr. Pass].

[lhquam]

Oops, the bottom cap (C2) should connect to V-, not ground. I am still tweaking a few things about this schematic, mostly resistor values.
The general idea looks pretty good.

Originally Posted by lhquam

I decided that it was a bad idea to try to economize on the resistor count by connecting the TL431 REF pin to the bias circuit potentiometer. Here is a revised schematic. This also restores the resistor charging the bias capacitor to somewhere near 10K ohms.

[buzzforb]

I think nelson may use something similar to bias his PP output stages.