New Lin 3 stage design anyone?

[sam9]

To follow up from a few posts back, I tried two otherwise identical versions of Self-type amp except one had completely separate CC networkks for input and VAS. In of themselves there didn't seem to be any inate performace advantage either way. However, the version with two independant CCs was easier to work with. One cab have the bias set by diodes and the other by a transistor. Being able to deal with each separately is plus for those of us with less experiance or bran power.

 

[hugonot]

from other hand

Hi bmcevers. Circuit is only a part of good amplifier. Especially when it is very complex amp with a big amount of negative feedback. I think, now is a good time to think about job you have to do to put those all parts together.

Good luck.

 

[mikek]

oh..

...refer your 2-pole compensation network to input ground, and not the -ve supply rail.......

....improves psrr at the top audio freqs.

 

[mikeks]

I must say that I find the NE5532 to be about the best compromise of opamp designs that are tailored towards audio. In Electronics, which is sector of Physics, there is no free lunch.

Designs are typically about compromise. You obtain one attribute only to give up another and I feel the NE5532, although a dated design, is very, very hard to beat.

The AD797 will only beat it with low source impedences at high gains (touchy near unity gain). The OPA627 is a good all around performer with the added benefit of low offsets (which I find is of little benefit in small signal audio) and beats the NE only with high source impedence. It doesn't have the desirable common mode characteristics of the NE5532 either.

Speaking of the NE5532, that brings me to Douglas Self. Yes, another one of my heroes. His books are straight-forward, practical and insightful.

Douglas Self has spent a large portion of his life de-mystifying distortions and non-linearities that have plagued audio design for years, he is truly passionate about his work.

His reasons for disliking MOSFETS, exotic opamps and the like are based in solid reasoning (MOSFET=expensive, lower gm, NE5532 overall outperforms 99% of opamps in the audio spectrum ).

This may sound like non-esoteric 'drivel' to some but I really believe that any alteration of an input signal is bad (ok, maybe a nice mesa guitar amp does sound good, but in my opinion a guitar amplifier is an integral part of the total instrument).

I subscribe to "an audio amplifier should be a straight wire with gain" camp. Harmonics of any order are just that: 2nd, 3rd, 5th it doesn't matter, they are deviations of the input, bottom line. If the "sonic truth" is out there, we should strive to eliminate them..........

Good Man!

 

[mikeks]

Re: oh..

...refer your 2-pole compensation network to input ground, and not the -ve supply rail.......

....improves psrr at the top audio freqs.

OOOPS...

Actually the opposite is true....Sorry!

 

[tlf9999]

His books are straight-forward, practical and insightful.

that is precisely his "crime": he made amps too simple and too easy, to the point that there is no room left for the "golden ear" type marketers, aka "high-end designers".

 

[mikeks]

Self created a world of trouble for himself by linking the input tail current source and the VAS current source, anyone who can afford a few small signal Qs should separate them. (but it has been amusing following Self’s acrobatics over the years as he tries to patch it up without adding a 20 cent transistor)

True..

Self's gymnastics in this regard were inexcusable....

Interesting because in the book he does recomend seperating the sources.

Nope...probably wishes he had...!

 

[mastertech]

Sam9-
"In of themselves there didn't seem to be any inate performace advantage either way. However, the version with two independant CCs was easier to work with. "
--------------------------------------------------------
i agree with the performance part...

 

[mastertech]

tlf9999-
that is precisely his "crime": he made amps too simple and too easy
------------------------------------------------
no he didnt, this guy doesnt know what design really is, if that is
design then you have no idea how i do it (maths Einstein)

cheers

 

[lineup]

this guy (refers to Douglas Self) doesnt know what design really is,
if that is design then you have no idea how I do it (maths Einstein)

cheers

I think you are a bit too critical to Mr. Self, mastertech.
What I can understand your own designs are better .....

Maybe somewhere you have told, published or posted some of your ideas, if you really have any.
But unfortunately I havent had the great luck of seeing nothing yet.
Isnt it time to let us know, if it is just bigtalking or anything for real?

 

[mastertech]

lineup i am really sorry, i have no great ideas

i merely made the point of lack of maths in his design book
a highly engineered product is mathed to the highest degree

now to the point of being critical to him without maths what is
he doing Einstein what is he doing with maths i'll tell you why
maths is the language of science Douglas as an objectivist/scientist left it out of context completely how can i
not be critical of him, how can i sit back and relax when he says
that subjectivism/philosophy has no place in science he is infact
a subjectivist himself when in a scientific field writes a book with
no maths

Kind Reagrds
Mastertech