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Old 13th December 2004, 01:11 PM   #11
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I checked for you, the downloads are still on his site.

http://www.borbelyaudio.com/adobe/dc102.pdf

http://www.borbelyaudio.com/adobe/classa.pdf

You wanted something hard to build.
You got it , chum.
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Old 13th December 2004, 01:33 PM   #12
anli is offline anli  Russian Federation
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Quote:
Originally posted by PMA
I was thinking about similar circuit you are speaking about, but did not find time enough to realize - maybe later.
Pavel,

I'm very interested in your researchings and is waiting for
your new schematics/measurements/concepts with impatience :-)

Andrew
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Old 13th December 2004, 01:36 PM   #13
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Another suggestion :

Norman E. Thagard's design published in Januari/Februari 1995.

Also a modular design, with dual powerlines for the front and the output stage, with bipolar/Mosfet cascode output stages
(MJ15024-MJ15025-IRF511-IRF9521)

Intended for 100 watt Class A, but also with separate voltages for the voltage and current amplifier. The voltage and bias of the output stage can be lowered to the desired need.
This amplifier can drive just about anything, the output has a maximum dissipation of 3500 watts.
In musical terms it does not rank highest on the list of amps i built.

I built a number of Class A push pull Mosfet amplifiers with dual powersupplies.
In my view the obvious choice, the total cost for the powersupply is lower, dual powersupplies have a natural separation and add to stability.
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Old 13th December 2004, 01:40 PM   #14
anli is offline anli  Russian Federation
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Quote:
Originally posted by jacco vermeulen
I checked for you, the downloads are still on his site.

http://www.borbelyaudio.com/adobe/dc102.pdf

http://www.borbelyaudio.com/adobe/classa.pdf

You wanted something hard to build.
You got it , chum.
Jacco, thanks!

I have found the articles too :-) I have looked at them during few
seconds and have not found any new ideas yet; nevertheless I think
I'll read them more deepply: sometimes even little things may be
usefull (in Russian we say "raisins" :-).
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Old 13th December 2004, 01:45 PM   #15
zinsula is offline zinsula  Switzerland
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Check out this one:

http://www.diyaudio.com/forums/showt...963#post334963

(the zip file at the end of the post)

balanced, symmetrical, no feedback, MOSFET output, etc.

Maybe one wants to use other output devices, but replacing them doesn't seem to difficult. And you may bias them up to the level you want. If it has too much power, you may reduce the voltage of output stage rails....

Ciao, Tino
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Old 13th December 2004, 02:17 PM   #16
anli is offline anli  Russian Federation
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Quote:
Originally posted by jacco vermeulen
Another suggestion :

Norman E. Thagard's design published in Januari/Februari 1995.
...
Jacco,

Which design do you mean? I have googled and got lost among
refs to Thagard's book :-(

Andrew
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Old 13th December 2004, 02:29 PM   #17
anli is offline anli  Russian Federation
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Quote:
Originally posted by zinsula
Check out this one:

http://www.diyaudio.com/forums/showt...963#post334963
...
Ciao, Tino
Tino, thanks! It is interesting for me, as the schematics resembles me my
own (deprecated by me: my view to audio design is shifted now slightly) project:

DoSuSy - LTspiced project. Comments?

Last project schematics version is here:

http://freedns.ru/andrew/dosusy/DoSuSy-0.31.pdf

Andrew
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Old 13th December 2004, 03:16 PM   #18
zinsula is offline zinsula  Switzerland
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Quote:
Originally posted by anli
Tino, thanks! It is interesting for me, as the schematics resembles me my
own (deprecated by me: my view to audio design is shifted now slightly) project:
You're welcome. Why did you change your view of audio design, and in what direction exactly? At least, your project was symmetrical, balanced, had mosfets....and feedback.

Ciao, Tino
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Old 13th December 2004, 03:44 PM   #19
anli is offline anli  Russian Federation
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Quote:
Originally posted by zinsula


You're welcome. Why did you change your view of audio design, and in what direction exactly? At least, your project was symmetrical, balanced, had mosfets....and feedback.

Ciao, Tino
Tino (well, is "Tino" your name? :-),

After reading plenty of (often disputable) articles, now I think:

1. each stage (input-gain-driver-output in common topology) _must_ have
own clean spctrum. Saying "clean spectrum" I mean quick lowering of
harmonics (something like 40db between 3d and 5th, for example).
Here I can accept the case when first even and first odd harmonics may be
even about -(40-60)db ;

2. global NFB commonly brings more difficulties rather advantages (due to needed
frequency correction each active part is not used as well as it can; global NFB
lag; as a reslt - harmonic spectrum is far from state-1); more advanced
designers may add plenty of info about other global NFB surprises, but see
this post end words :-)

3. global NFB introduces own distrotions, which are not commonly measured, but
our ears listen them well. As the aim is an amplifier for home use, I don't
want an amplifier wich is excellent for market, I want an amplifier to be excellent
for my and my friends music emotions.

There are many threads here concerning listed states. I'd like to emphasize,
I'll be happy this one will be about _concrete_ schematics designs rather
unending theoretical disputes :-)

Let's try!
Andrew
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Old 13th December 2004, 06:50 PM   #20
Marc Vi is offline Marc Vi  Netherlands
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I’ am designing a fully discrete balanced symmetrical DC coupled class A amplifier with no global feedback using transistors (but Mosfets are also possible). A DC servo (with opamp) is possible but not necessary. The circuit will not be complex and will be rather easy to build. The costs will be fairly low, depending on the parts you use. The power will be about 35 W at 8 ohm.

I will publish the circuit in Christmas holidays.

Marc.
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