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Old 19th September 2010, 12:53 PM   #1
lineup is offline lineup  Sweden
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Default SymFet - The Small Amplifier

Inspiration is Jean Hiraga. He did some minimalistic amplifiers.
He put only those things in that were absolutely necessary.
He even tried to remove as many transistors as possible.
He also knew that there is a difference between quality & quantity.
100 Watt is not necessarily giving more pleasure than 5 good Watt.
Have a look at his Monster. With 5 Watt in Class A and +/-12V supply!


Once you can get a hold of & match 2SK170BL and 2SJ74BL,
then this amplifier will be easy to build.
Works at +/-12V in Class AB, with MJ15003/MJ15004.

Three components to adjust.
- Adjust R4 for 5 mA across R1 and R8.
- Adjust voltage source V2 för 50mA idle in output.
- Adjust R9 for close to 0.0V output DC-Offset.
...Note: You may have to put R9 at the upper side. Across R1.

Spice measurements:
Max 5.77 Watt into 8 Ohm, <0.100% THD
Max 10.9 Watt into 4 Ohm, <0.100% THD
Nominal 1 Vrms input gives 5.4 Watt into 8 Ohm and 0.011% THD
1 Watt RMS into 8 Ohm gives 0.005% THD
Upper frequency is 500kHz with C1 75pF.


=============

Finally, this was one more circuit idea by me.
I have publish many through the years.

If this amplifier had been presented by John Curl or even Nelson Pass
there would be instantly 100-reds of guys rushing to the electronics shops
to get the stuff to build this amplifier.

And this topic would go on for decades with thousands of replies
and constant discussions about this genious design of the guru.

Will it stop me from publish my ideas, that I know they will never be used?
No. I believe in my stuff. I know some of my ideas are great.
Maybe someday, some guy will read this and see the beauty.
On that day I probably will be dead and buried.
Eventhough the state of things make me a bit sad,
this will not stop me from doing what I do.
And so at least feel content.
I only did what I had to do - being me
... Lineup
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Old 19th September 2010, 01:18 PM   #2
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What is the software you used to simulate this circuit ? I like the instrument-like THD gauge.
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Old 19th September 2010, 01:25 PM   #3
sekhar is offline sekhar  India
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Quote:
Originally Posted by fireworks View Post
What is the software you used to simulate this circuit ? I like the instrument-like THD gauge.
it is multisim




regards
sekhar
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Old 19th September 2010, 01:29 PM   #4
wahab is offline wahab  Algeria
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Quote:
Originally Posted by lineup View Post
If this amplifier had been presented by John Curl or even Nelson Pass
there would be instantly 100-reds of guys rushing to the electronics shops
to get the stuff to build this amplifier
And this topic would go on for decades with thousands of replies
and constant discussions about this genious design of the guru.


... Lineup

Hi , Lineup
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Old 15th November 2010, 06:59 AM   #5
Yarpen is offline Yarpen  Poland
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Hi lineup

i'm looking for a good AB class 20-25W amplifier
Is it possible to increase the power of this circuit? Could you simulate its behavior for about 24V power supply?
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Old 15th November 2010, 07:19 AM   #6
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Quote:
Originally Posted by lineup View Post
Inspiration is Jean Hiraga. He did some minimalistic amplifiers
fine
but eek
gnfb!
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Old 15th November 2010, 09:03 AM   #7
forr is offline forr  France
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Hi Lineup,
Hiraga amps had quite high ouput impedance and low PSRR, needing huge power supplies. As far as I see, yours is better.
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Old 15th November 2010, 09:24 AM   #8
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Wahap,

I'm interested in this lovely small amp.

It seems you are using Micro-Cap to simulate the circuit. Could you mind to send me the file so that I can do it on my computer?

Thanks,
circuitscc
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Old 21st January 2011, 10:44 AM   #9
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Quote:
Originally Posted by lineup View Post
Finally, this was one more circuit idea by me.
I have publish many through the years.

If this amplifier had been presented by John Curl or even Nelson Pass
there would be instantly 100-reds of guys rushing to the electronics shops
to get the stuff to build this amplifier.

And this topic would go on for decades with thousands of replies
and constant discussions about this genius design of the guru.
... Lineup
I believe in your design and concept.......and they do have potential

Kanwar
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Old 21st January 2011, 11:05 AM   #10
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One of the advantage is the input does not see the Cdg of J1 and J2 as their

co-jointed gates is at virtual ground, provided that dynamic impedance of V5 is zero.

Anyone has made a circuit board for this project?
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