Sziklai pair - 1fet+1bjt.

[lineup]

1. Someone say these graphs tell nothing.
Others propose them as valuable.

2. I could not enter your web site.

beppe61
Thank you Sir.

1. Different opinions on simulations, yes.
They do not show exactly how circuit will do.
They can tell a little about if a circuit will do alright.
And also say if a change will probably be for better or not.

A good experienced designer do not use simulations much.
Because he knows better in his mind, what is good and not so good.
And what will work alright in real circuit.

Some people do simulations, because they have good programs for it.
They think it is fun and interesting.
It does not hurt to make simulations, but we should know
they not often tell:
The truth, The whole truth and nothing but the truth!

To make real measurment on a real circuit is much better.
For this you also need special test gears.
Now, real circuit tests use special test signals.
And special 'easy dummy loads'.
Most used is sinus waves and square waves.
Sometimes mixture of two waves of different frequencies.

Main drawback from this is,
that music is a much more complex mixture of waves.
And headphones and loudspeakers are not easy, but more complex loads.


The most difficult job for an audio circuit,
will be playing music into real sound reproducing loads.
- Simulation of a schematic diagram is very far from this.
- Measurment test of a real circuit is closer, but still not close to playing music.

===========


2. My website has only one startpage, but no working link.
I plan to put up some stuff.

You have any idea beppe61, what I should put into my website?
What would you like to see?

Regards
lineup

 

[beppe61]

> Different opinions on simulations, yes.
They do not show exactly how circuit will do.
They can tell a little about if a circuit will do alright.
And also say if a change will probably be for better or not.

- Very useful so but not the last word about the sound quality of a topology. I see. Thank you.

> A good experienced designer do not use simulations much.
Because he knows better in his mind, what is good and not so good. And what will work alright in real circuit.
- Interesting. Do they do any calculation of the circuit ?

> Some people do simulations, because they have good programs for it.
They think it is fun and interesting.
It does not hurt to make simulations, but we should know
They not often tell: The truth, The whole truth and nothing but the truth![/B]
- I see. My question is: a circuit that behaves well in real situations does simulate well or not ?
I mean: there must be a starting point. A first raw design.
Which is the method to carry out this first raw design ?

> To make real measurment on a real circuit is much better.
- No doubts about this.

> For this you also need special test gears.
Now, real circuit tests use special test signals.
And special 'easy dummy loads'.
Most used is sinus waves and square waves.
Sometimes mixture of two waves of different frequencies.
- I see your point: designers develop their own procedures and systems for measurements. And these are part of their know-how.

> Main drawback from this is, that music is a much more complex mixture of waves.
And headphones and loudspeakers are not easy, but more complex loads.
- So they are not easy to model. I see.

> The most difficult job for an audio circuit, will be playing music into real sound reproducing loads.
- Simulation of a schematic diagram is very far from this.
- Measurment test of a real circuit is closer, but still not close to playing music.

- Very demanding task I suppose.

2. My website has only one startpage, but no working link.
I plan to put up some stuff.
You have any idea beppe61, what I should put into my website?
What would you like to see?
Regards
lineup

- Well I think you could start with a page explaining your approach to audio equipment designing/testing.
Personally I find extremely interesting to read opinion from different designers, due to the lack of one only truth.

Thank you very much again.
Kind regards,

beppe

 

[forr]

Hi BEPPE61

John Linsley-Hood used such a FET-BJT pair in his FM tuner and in a push-pull buffer version (with positive and negative power supplies) in one of his preamps .

~~~~~ Forr

§§§

 

[Miles Prower]

At the cost to turn out monotonous I am attaching an example of
sziklai pair.
I would like to replace the input bjt with a nice fet and so avoiding the input cap.

Thank you for your patience.
Kind regards,

beppe

I would also point out that this is not a Sziklai Pair. What that is is two common emitter voltage amps in series with a NFB loop.

The Sziklai Pair is a Darlinton-like arrangement which uses an input NPN with a PNP to simulate an NPN transistor and vice versa. It's the same idea behind the quasicomp topology, except that there are two of them. This topology has the advantage of better temp stability since there is just one V(BE) drop to contend with instead of two. Since it also has local NFB, it's supposed to have improved sonics as well. Some folks do indeed report that this is the case. (Of course, whether this is simply a self-fulfilling (no pun intended) prophecy because Doug Self said so, or not is a whole 'nother story.) There is a price to be paid for this in that Sziklai Pairs tend to instability.

Sziklai Pair

 

[x-pro]

Dear Mr. Alex,

may I ask you wich software have you used to simulate the circuit ?

It is free LTSpice/SwitcherCAD III, available from http://www.linear.com .

I would like to ask you another thing.
Do you think that "playing" with the value of R1, R2 and R3 and/or the V2 value it would be possible to get an even better distortion spectrum ?

In a simulation it looks possible, however I never tried it in real life. Would be interesting, thought.

x-pro

 

[beppe61]

1) It is free LTSpice/SwitcherCAD III, available from http://www.linear.com .
2) In a simulation it looks possible, however I never tried it in real life. Would be interesting, thought.
x-pro

Dear Sir,

first all my sincere congratulations for your excellent designs you have uploaded and disclosed for anyone's use in this site.
Thank you very much indeed.
1) Thank you for the advice. I will try to use it, but I am not very good at electronics.
2) I feel the same.
I find exceptionally interesting the simulations softwares.
I understand that their capabilities and qualities are variable.
The possibility to fine-tune a circuit without having to actually buils it it is very amazing.
Have you ever had the opportunity to compare the distortion spectrum calculated by the sim software with that coming out from an oscilloscope?
Honestly I have to tell you that if I were smarter and richer (because experimenting involves costs after all) this would be my mission.
I saw a tv movie about Mr. Albert Einstein.
What amazed me was His mission to explain every physical phenomenon on a mathematical basis.
And what is sound if not a physical phenomenon after all?
If only Albert had been interested in high-fidelity !

Thank you very much indeed for your excellent contribution to this site.
Kind regards,

beppe

 

[beppe61]

Hi BEPPE61
John Linsley-Hood used such a FET-BJT pair in his FM tuner and in a push-pull buffer version (with positive and negative power supplies) in one of his preamps .
~~~~~ Forr
§§§

Very interesting.
So the topology should be intrinsecally valuable.
And also very easy to build.
I like Sziklai pair more and more day after day.

Thank you very much indeed.
Kind regards,

beppe

 

[beppe61]

Originally posted by x-pro
1) It is free LTSpice/SwitcherCAD III, available from http://www.linear.com .
2) In a simulation it looks possible, however I never tried it in real life.
Would be interesting, thought.
x-pro

Dear Sir,

first all my sincere congratulations for your excellent designs you have uploaded and disclosed for anyone's use in this site.
Thank you very much indeed.
1) Thank you for the advice. I will try to use it, even if I am not that clever.
Nevertheless I am very intriguing about simulation software.
Ok. They are not the "real thing" but the very best ones could be very "realistic".
2) I feel the same.
I find exceptionally interesting the simulations softwares.
I understand that their capabilities and qualities are variable.
The possibility to fine-tune a circuit without having to actually buils it it is very amazing.
Have you ever had the opportunity to compare the distortion spectrum calculated by the sim software with that coming out from an oscilloscope?
Honestly I have to tell you that if I were smarter and richer (because experimenting involves costs after all) this would be my mission.
I saw a tv movie about Mr. Albert Einstein.
What amazed me was His mission to explain every physical phenomenon on a mathematical basis.
And what is sound if not a physical phenomenon after all?
If only Albert had been interested in high-fidelity !

Thank you very much indeed for your excellent contribution to this site.
Kind regards,

beppe

 

[RCruz]

Beppe,

here is a possible schematics and results of FFT simulation for 1V RMS output - the gain here is about 7. I did use similar gain stages in the past and if you have time to select JFETs, it could be a very good circuit.

Input here is directly coupled, however in real life you may decide to add a simple RC filter to remove RF, say 10K and 100pF.

Cheers

Alex

P.S. - I've edited the schematics to add the filter.

Hello Alex

I have a question about the Sziklai pair and would really apreciate your input: http://www.diyaudio.com/forums/solid-state/323937-sziklai-jfet-input-mc-pre-pre.html#post5463337