MEMDIST POWER AMP + JC + TMC - help to set up - diyAudio
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Old 25th January 2011, 09:25 AM   #1
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Join Date: Mar 2004
Location: Krakow
Lightbulb MEMDIST POWER AMP + JC + TMC - help to set up

Hi,
I was hot after reading about headamp from peufeu Memory Distortion Philosophies - Part 8 : More tests
and wanted to build higher power version for LS driving.
Please look at the schematic,
I added JC-like coupling within the mirror and VAS
then I wanted use TMC like gnfb correction like Edmond Stuart proposed Bob Cordell Interview: Negative Feedback
and got this.
Please help to adjust the values/other parameters to obtain the amp possible for working,
I believe that the combination of memdist/TMC correction might give something better that "Lavardin" sound.

Additional explain: I hate global nfb and believe that that solution in most cases spoils the sound,
however
with you help
will this be good sounding?
Attached Images
File Type: jpg memdist JC.jpg (95.2 KB, 241 views)
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regards, Pawel
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Old 28th January 2011, 10:07 AM   #2
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ok
here are initial settings
and sim results
Attached Files
File Type: pdf memdist power.pdf (31.7 KB, 53 views)
File Type: pdf memdist power-Transient-7-Graph.pdf (29.9 KB, 14 views)
File Type: pdf memdist power-Fourier-7-Graph.pdf (6.2 KB, 15 views)
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Old 28th January 2011, 10:10 AM   #3
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and here clipping
Seems that bad 2nd and 3rd harmonics are from the mistakes in the design.
Please advice how to set it more symmetric?
Attached Files
File Type: pdf memdist power-Transient-8-Graph.pdf (26.5 KB, 15 views)
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Old 28th January 2011, 12:56 PM   #4
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Unhappy simplified version

...
again
not too good...
Attached Files
File Type: pdf memdist simply.pdf (24.5 KB, 26 views)
File Type: pdf memdist simply-Transient-10-Gra.pdf (28.9 KB, 3 views)
File Type: pdf memdist simply-Fourier-10-Graph.pdf (6.2 KB, 5 views)
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Old 31st January 2011, 08:23 AM   #5
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Join Date: Mar 2004
Location: Krakow
it looks like input tripple clips the signal at 4V.
it is linear but clips...
how to improve its headroom?
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Old 31st January 2011, 09:03 AM   #6
WuYit is offline WuYit  Sweden
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Hi,
maybe you should pay a visit to: Cascoding the folded cascode
That`s a much better topology despite some flaws.
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Old 7th December 2011, 12:31 PM   #7
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Join Date: Mar 2004
Location: Krakow
Hi
after some time I designed something like this.
As input fet I am going to use BF245B but did not have the models.
The design seems to be a bit from the oscillations
please suggest how to make it more stable.
Attached Images
File Type: jpg memdistnewvas.jpg (99.5 KB, 113 views)
File Type: jpg sine.jpg (94.2 KB, 98 views)
File Type: jpg fft.jpg (99.4 KB, 85 views)
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Old 7th December 2011, 12:34 PM   #8
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and asc file for ltspice
Attached Files
File Type: txt memdistnewvas.asc.txt (9.7 KB, 3 views)
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Old 10th January 2014, 09:38 AM   #9
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Join Date: Mar 2004
Location: Krakow
Thumbs up rewarming memdist power

Hi
after some play with LTSpice I found that this time it is working.
Close to full power has very low thd and nice descending harmonics distribution @~110mA idle.
The circuit has the potential, maybe I will build it someday = needs 2SK170 or other 50V DC device instead of BF245B which is only up to 30V (only for simulations).
TMC nice lowered the thd.
asc file attached for play & fun
Attached Images
File Type: png sch.png (20.8 KB, 52 views)
File Type: png sims.png (66.4 KB, 31 views)
File Type: png acsmall.png (9.5 KB, 14 views)
File Type: png fft.png (11.7 KB, 17 views)
Attached Files
File Type: asc memdist fet sf inp.asc (12.0 KB, 7 views)
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Last edited by padamiecki; 10th January 2014 at 09:41 AM.
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