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Old 9th August 2014, 09:50 AM   #1
dadod is offline dadod  Croatia
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Default GainWire-NGNFB-classB-PowerAmp

Tanks to smms73 I can show here novel Error Correction circuit used in Non GNFB class B power amp.
I tried before with classic Hawksford Error Correction, but with not so good result as with th is novel EC. I Think that smms73 came to this idea by himself, an latter has found that this is also already presented by Hawksford.
The THD can be seen on the schematic.
This is not ready to be used as a working amp, as it needs to be more simulated and improved in some areas.
BR Damir
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Old 9th August 2014, 09:57 AM   #2
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Here are some FFTs for different power levels and different frequencies.
Damir
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Old 10th August 2014, 11:56 AM   #3
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This simulation shows how this EC is very efficient, 35 dB lower THD1k, and 25 dB lower THD20 when EC is active.
"error_resistor" is the place where the cancelation is happening, to defeat it, this resistor was shorted.
Damir
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Old 11th August 2014, 07:14 AM   #4
dadod is offline dadod  Croatia
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Clipping and square wave simulation. Slew Rate is 72 V/usec.
Damir
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Old 11th August 2014, 07:37 AM   #5
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outstanding performance even for class ab gnfb!
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Last edited by padamiecki; 11th August 2014 at 07:43 AM. Reason: one letter too much...
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Old 11th August 2014, 04:30 PM   #6
dadod is offline dadod  Croatia
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Quote:
Originally Posted by padamiecki View Post
outstanding performance even for class ab gnfb!
Thank you Pawel, you are very kind.

With this power amp, if used as integrated amp, volume control could be positioned on the input or of the current conveyor output, Rx1 to be variable.

For both cases there are one advantage and one disadvantage.
If potentiometer is at the input, the noise is higher, but distortion is lower at the low level.
If Rx1 is used as the volume, then distortion is higher and it's coming mostly from the input stage and in that way does not change with volume level, but the ratio signal to noise is the same for all volume settings, thus very low at low volume.
Damir
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Old 12th August 2014, 01:32 AM   #7
AKSA is offline AKSA  Australia
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I must say 17 ppm THD20 is exceptional, and even more impressive without global feedback....
However, it has to be laid out, built, and auditioned Damir, you have at least six months of work ahead to achieve this!!
How about asking AlexMM to lay it out - he is a genius in this work - then Borys for do the work, he is a very quick, clever builder.......

Sadly I'm too bloody old and slow now, I love this stuff but my hands are fall with my larger amp designs at present.

Cheers,

Hugh
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Old 12th August 2014, 03:35 AM   #8
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Hi Damir. Looking good .
May I suggest to split the project in two pcb , one for the voltage amplifier and another for the output stage ? That way will be easier to make changes in the future. If AlexMM would design the pcb as Hugh suggest it would be perfec , I have see some of his pcb designs and they are very good.
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Old 12th August 2014, 05:47 AM   #9
dadod is offline dadod  Croatia
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Quote:
Originally Posted by AKSA View Post
I must say 17 ppm THD20 is exceptional, and even more impressive without global feedback....
However, it has to be laid out, built, and auditioned Damir, you have at least six months of work ahead to achieve this!!
How about asking AlexMM to lay it out - he is a genius in this work - then Borys for do the work, he is a very quick, clever builder.......

Sadly I'm too bloody old and slow now, I love this stuff but my hands are fall with my larger amp designs at present.

Cheers,

Hugh
Thank you Hugh, and you are so right, I am old too and slow. So many project and so little finished. Somebody could ask why? Those simulations are very good brain exercise(to keep it young ha ha) and to build all that asks for agility and strength of youth.
Yes, of course a help from those PCB layout expert is very welcome. I think that I have to check the output, to see if a zobel or coil needed for capacitive load.
Cheers,
Damir
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Old 12th August 2014, 05:51 AM   #10
dadod is offline dadod  Croatia
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Quote:
Originally Posted by smms73 View Post
Hi Damir. Looking good .
May I suggest to split the project in two pcb , one for the voltage amplifier and another for the output stage ? That way will be easier to make changes in the future. If AlexMM would design the pcb as Hugh suggest it would be perfec , I have see some of his pcb designs and they are very good.
Sergio you suggestion to split it on two boards is good. I will divide schematic in two part.
What do you think of needs for zobel and coil at the output, I don't have practical experience with the non GNFB amps?
BR Damir
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