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Old 19th June 2014, 07:09 PM   #21
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Hi and thank you All for the very interesting 3D
May i ask you which are the main benefits of the simmetrical arrangement ?
A single pair would measure significantly worse ?
I have in mind this kind of circuits to buffer the signal after a pot for line stage duties.
Very interesting 3D.
Thanks, gino

Last edited by ginetto61; 19th June 2014 at 07:21 PM.
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Old 19th June 2014, 08:29 PM   #22
dadod is offline dadod  Croatia
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Quote:
Originally Posted by ginetto61 View Post
Hi and thank you All for the very interesting 3D
May i ask you which are the main benefits of the simmetrical arrangement ?
A single pair would measure significantly worse ?
I have in mind this kind of circuits to buffer the signal after a pot for line stage duties.
Very interesting 3D.
Thanks, gino
That buffer was intended to drive low ohmic headphones. For lineamp only, you can use simpler buffer as this here in the beginning of this thread JLH Buffer - Homage to John Linsley Hood, or you can use something as Pass B1 buffer. With symmetrical arrangement you can have no caps in the signal path.
Damir
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Old 20th June 2014, 06:28 AM   #23
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Hi and first sorry for the belated reply.
I am very interested in very good line driver/buffer designs because i really want to try a buffered volume control.
I have noticed that very decent power amps can be found quite easily.
Good line stages are much much less common
One of the main problem with SS is the 3D ability, while tubes are generally very good at this, but with other drawbacks that i do not like at all like soft bass and limited highs.

Quote:
Originally Posted by dadod View Post
That buffer was intended to drive low ohmic headphones.
For lineamp only, you can use simpler buffer as this here in the beginning of this thread JLH Buffer - Homage to John Linsley Hood, or you can use something as Pass B1 buffer.
With symmetrical arrangement you can have no caps in the signal path.
Damir
Thanks a lot for your valuable advice.
I am not worried about caps in the signal path but i wonder how much performance can be obtained from an even simpler buffer gain stage, let's say with just a half of your really nice and elegant design, even if this of course will require the use of coupling caps.
A general schematic like the one here

Click the image to open in full size.

I have the feeling that a basic circuit well optimized, with the right layout and parts selection can give very high performance.
This "optimization" is not that easy process at all.
And on this basis i do not like very complex design because if it is difficult to optimized very basic circuits just think what kind of task is to optimized complex one.
I have always this KISS principle in my mind, even if i was looking at a very good preamp, the MBL 6010D and remained a little perplexed.
On the back there is written
Quote:
High speed - single gain stage - design
Then you open it and it is full of opamps
In conclusion i would like to understand, before complicating the task, how much performance can i get from a two bjts buffer (i prefer bjts to fets).
My feeling is that a lot of performance can be got when all things are optimized.
First thing will be to try using some sim SW and see.
Thanks again and kind regards, gino

Last edited by ginetto61; 20th June 2014 at 06:38 AM.
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Old 20th June 2014, 09:58 AM   #24
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Dadod, do you try Hiraga 8w or 20w output stage ?

http://diyaudioprojects.com/Solid/Je...s-A-Amplifier/

http://diyaudioprojects.com/Solid/Je...ga-Le-Monstre/

Last edited by UltimateX86; 20th June 2014 at 10:19 AM.
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Old 20th June 2014, 10:24 AM   #25
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Quote:
Originally Posted by ginetto61 View Post
Hi and first sorry for the belated reply.
I am very interested in very good line driver/buffer designs because i really want to try a buffered volume control.
I have noticed that very decent power amps can be found quite easily.
Good line stages are much much less common
One of the main problem with SS is the 3D ability, while tubes are generally very good at this, but with other drawbacks that i do not like at all like soft bass and limited highs.



Thanks a lot for your valuable advice.
I am not worried about caps in the signal path but i wonder how much performance can be obtained from an even simpler buffer gain stage, let's say with just a half of your really nice and elegant design, even if this of course will require the use of coupling caps.
A general schematic like the one here

Click the image to open in full size.

I have the feeling that a basic circuit well optimized, with the right layout and parts selection can give very high performance.
This "optimization" is not that easy process at all.
And on this basis i do not like very complex design because if it is difficult to optimized very basic circuits just think what kind of task is to optimized complex one.
I have always this KISS principle in my mind, even if i was looking at a very good preamp, the MBL 6010D and remained a little perplexed.
On the back there is written
Then you open it and it is full of opamps
In conclusion i would like to understand, before complicating the task, how much performance can i get from a two bjts buffer (i prefer bjts to fets).
My feeling is that a lot of performance can be got when all things are optimized.
First thing will be to try using some sim SW and see.
Thanks again and kind regards, gino
This is a so called "Schiklai", or CFP, arrangement. In order to make its performance as linear as possible, you need to load it with a constant current source (dynamic load), which will take another couple of transistors (at least)

Also, it is important to understand the input/output impedance requirements for the buffer - in many cases additional stage may be required just to satisfy those.

Yes, simulation will help...
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Old 20th June 2014, 11:02 AM   #26
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Quote:
Originally Posted by vzaichenko View Post
This is a so called "Schiklai", or CFP, arrangement.
In order to make its performance as linear as possible, you need to load it with a constant current source (dynamic load), which will take another couple of transistors (at least)
Also, it is important to understand the input/output impedance requirements for the buffer - in many cases additional stage may be required just to satisfy those.
Yes, simulation will help...
Hi and thank you very much indeed for your valuable advice
So you mean that a stage like the one attached has no chance to be linear and extremely low in distortion ?
This is a very fundamental question for me at this stage.

Anyway ... i understand that i am quite alone in seeing the challenge of achieving extremely good performance with extremely simple topologies
Maybe i am mistaking but i remember at least one very famous designer saying that after all his simpler (topology wise) designs were also the better sounding.
Personally i would start from that statement when selecting a suitable design, at least for a line stage that is the my major and almost only interest.
I wonder if someone is so nice to simulate it for me ... just for fun.
It could be a surprised.
The single supply voltage is 0-60V and the bjt can be almost all signal/driver pnps and npns. The pnp tends to heat up a little.
Kind regards, gino
Attached Images
File Type: jpg input gain stage.jpg (198.2 KB, 220 views)

Last edited by ginetto61; 20th June 2014 at 11:14 AM.
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Old 20th June 2014, 01:11 PM   #27
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Originally Posted by UltimateX86 View Post
No, I never tried any of those amps.
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Old 20th June 2014, 02:43 PM   #28
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Quote:
Originally Posted by ginetto61 View Post
Hi and thank you very much indeed for your valuable advice
So you mean that a stage like the one attached has no chance to be linear and extremely low in distortion ?
This is a very fundamental question for me at this stage.

Anyway ... i understand that i am quite alone in seeing the challenge of achieving extremely good performance with extremely simple topologies
Maybe i am mistaking but i remember at least one very famous designer saying that after all his simpler (topology wise) designs were also the better sounding.
Personally i would start from that statement when selecting a suitable design, at least for a line stage that is the my major and almost only interest.
I wonder if someone is so nice to simulate it for me ... just for fun.
It could be a surprised.
The single supply voltage is 0-60V and the bjt can be almost all signal/driver pnps and npns. The pnp tends to heat up a little.
Kind regards, gino
Simulation - easily

First picture shows the setup
With 36V power supply, collector current of Q1 = 330uA, Q2 = 5mA
Voltage gain = 10db
Frequency response - linear up to around 300KHz

Second picture - output swing 1.12V RMS @ 1KHz
Third picture - same swing @ 20KHz
Forth picture - same as the third one, but showing the phase responce instead of the frequency one

Harmonics distribution is nice.
Lower power supply voltage leads to significant distortion increase.

If you have questions - let me know

Cheers,
Valery
Attached Images
File Type: jpg 01-schematic.JPG (52.6 KB, 197 views)
File Type: jpg 02-output-1K.JPG (226.2 KB, 177 views)
File Type: jpg 03-output-20K.JPG (223.6 KB, 54 views)
File Type: jpg 04-output-20K.JPG (226.4 KB, 48 views)
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Old 20th June 2014, 03:40 PM   #29
dadod is offline dadod  Croatia
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Quote:
Originally Posted by vzaichenko View Post
Simulation - easily

First picture shows the setup
With 36V power supply, collector current of Q1 = 330uA, Q2 = 5mA
Voltage gain = 10db
Frequency response - linear up to around 300KHz

Second picture - output swing 1.12V RMS @ 1KHz
Third picture - same swing @ 20KHz
Forth picture - same as the third one, but showing the phase responce instead of the frequency one

Harmonics distribution is nice.
Lower power supply voltage leads to significant distortion increase.

If you have questions - let me know

Cheers,
Valery
Valery, you are fast. When you are going to switch to LTspice as most members here are using it, and will be much easier to exchange .asc files between?
Dammir
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Old 20th June 2014, 03:51 PM   #30
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Join Date: Sep 2009
Location: Stavanger (NORWAY)
Quote:
Originally Posted by vzaichenko View Post
Simulation - easily

First picture shows the setup
With 36V power supply, collector current of Q1 = 330uA, Q2 = 5mA
Voltage gain = 10db
Frequency response - linear up to around 300KHz

Second picture - output swing 1.12V RMS @ 1KHz
Third picture - same swing @ 20KHz
Forth picture - same as the third one, but showing the phase responce instead of the frequency one

Harmonics distribution is nice.
Lower power supply voltage leads to significant distortion increase.

If you have questions - let me know

Cheers,
Valery
Hi and first of all thank you very much indeed
I would not hope such amazing and very kind help
Yes ... i have a question ... how did you do that ?
My dream would be one day to be able to do the same myself
Please let me know what i have to do/buy
I am seriously interested and the results look fantastic !
Thanks a lot again
Kindest regards, gino
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