O.H. Schade(1938) meets MOSFET - Page 3 - diyAudio
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Old 6th October 2009, 04:55 AM   #21
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When you look at the circuit, you have to realize that this
is a mild form of negative feedback. It points to a
possible equivalence between low amounts of negative
feedback and the effect of plate-cathode voltage on the
transconductance figure of a triode.

When you work a load line so as to cancel these two
distortions, the result is lowered 2nd harmonic but the
appearance of 3rd and other harmonics, similar to
Baxandall's analysis of negative feedback.

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Old 6th October 2009, 07:59 AM   #22
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Hey Nelson,

Are you reffering to Paravicini or Schade?

If it is Schade I´d say the local NFB is gross.
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Old 6th October 2009, 10:39 PM   #23
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I was thinking of the diagram in post #4, specifically.

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Old 8th October 2009, 12:16 AM   #24
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I was browsing through Horowitz and Hill (a little light after-
work reading) and noticed the "Fet linearizing" circuit which
is used to straighten out the characteristics of fets used as
variable resistors. It is another example of this technique,
but it's used to straighten out the curves at low voltages.

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Old 17th November 2009, 11:42 AM   #25
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Reread Linsley-Hoods LINIAC article from -71 the other day and saw some similarities to what have been delt with here.

If we combine the Schaded 2SK170 with a "voltagecontrolling" gyrator and a SF we are there.
One could of course take the NFB from the output but does a SF really need more NFB?

Using a P-channel output device there is no need for insulation against the heatsink as drain is to ground.

RDC is used to achieve symmetrical clipping.

Unfortunately the gyrator needs additonal voltage to work. If instead a choke was used the 24V would be enough. The gyrator FET doesn´t need to be depletion, anything with high Gm will do.
Attached Images
File Type: png GyroZen.PNG (57.0 KB, 615 views)

Last edited by revintage; 17th November 2009 at 11:45 AM.
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Old 24th January 2011, 02:09 AM   #26
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Quote:
Originally Posted by revintage View Post
Reread Linsley-Hoods LINIAC article from -71 the other day and saw some similarities to what have been delt with here.

If we combine the Schaded 2SK170 with a "voltagecontrolling" gyrator and a SF we are there.
One could of course take the NFB from the output but does a SF really need more NFB?

Using a P-channel output device there is no need for insulation against the heatsink as drain is to ground.

RDC is used to achieve symmetrical clipping.

Unfortunately the gyrator needs additonal voltage to work. If instead a choke was used the 24V would be enough. The gyrator FET doesn´t need to be depletion, anything with high Gm will do.
Lars, how was your test result?
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Old 8th October 2012, 04:47 PM   #27
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Quote:
Originally Posted by tiefbassuebertr View Post
I guess, that the M100A (M 100 A, M100) from "Esoteric Audio Research" (EAR, Tim Paravicini) could be a commercial product with similar circuit topology inside - please go to the weblinks
hi-fi, home cinema and multi-room audio and video specialists in Poole, Dorset | stoneaudio.co.uk
http://www.savantaudio.com/earm100.html
EAR/Yoshino 834T Integrated Amplifier Review By Dick Olsher
M100A
the detailed description is to find by the last weblink, but only in German
perhaps anybody has a detailled schematic diagram and photos from inside of this power OT-SE power amplifier

Quote from
Music, Sound and Personalities: 2001 CES by Dave Glackin
The Best Un-Solid-State-Like Solid State Electronics (Tie) were from Tim deParavicini of Esoteric Audio Research. Tim was demonstrating the M100 A single-ended solid-state Class A transformer-coupled 100W monoblock power amps with his model 312 solid state transformer-coupled preamp ($35,000 and $18,000, respectively). Speakers were the Kharma Ceramic 1 Limited Edition. Solid state is quite a departure for Tim, but the beautiful sound that he was getting spoke for itself. It didn't sound like solid state or tubes, but it did sound an awful lot like music. You can contact E.A.R. USA via phone at (562) 422-4747 or via fax at (562) 422-6577 in Long Beach, California. (That's so retro.) You'll find Kharma at www.kharmausa.com.
Quote from
Paravicini M100A Twin Tower2
Paravicini M100A First Solid State Single Ended Power Amplifier The M100 monoblock power amplifier, EAR/Yoshino’s second venture into solid state. Tim de Paravicini has burned the rulebook as usual, producing a pure Class A, single ended, 100W monster which combines awesome sonic authority with exquisite filigree detail. Unique circuit design - including one of Tim’s legendary output transformers - ensures the perfect match between the traditional audio virtues of valves and transistors. Superb construction, great looks, novel heatsinks (no perilous sharp edges - and no noisy fans!), high reliability, extraordinary pride of ownership. Discerning audiophiles prepared to lose some serious weight in the wallet department will need little persuading. Specifications Maximum output: Frequency response (at 1W output): Power bandwidth: Input impedance: Damping factor: Sensitivity: Residual noise (volume at minimum): Distortion: Max. Size (overall, excluding control knobs): Weight (nett): 100W (28VRMS on 8 ohm terminals) -3dB at 3Hz, 40kHz -3dB at 20Hz, 40kHz 47kohm 8 1V for full output 0.5mV 2% at full power W 240mm, D 500mm, H 570mm 70kg Yoshino Ltd. Coombe Grove Farm, Ermine Way, Arrington, Cambs. SG8 0AL Tel No. +44 (0) 1223 208877, Fax No. +44 (0) 1223 208761
Are there a schematic available in the meantime?

Measuring results are to find here:
EAR/Yoshino M100A monoblock power amplifier Measurements | Stereophile.com
and the listening test results here:
EAR/Yoshino M100A monoblock power amplifier | Stereophile.com
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Old 5th November 2012, 02:41 PM   #28
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Quote:
Originally Posted by revintage View Post
So what happens if we adapt what Schade taught us to a JFET as buffer?

Works like wonders !

Zout below 200ohms, together with low THD and acceptable bandwith (-3dB at well over 200kHz). Zin chosen to 10kohm. With 22kohm/91k bandwith is 100kHz.

But don´t try to a volume-pot at the input! Must be fed from a lowZ source.
Hello revintage. A bjt has pentode-like characteristic curves. Will your methodology of this post also apply to a bjt; meaning a bjt sounding like a triode?
Brgds.
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Old 7th November 2012, 04:36 PM   #29
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Just for fun, I traced some curves for the NTE451 JFET that show the effect of parallel feedback. It indeed works as advertized (on the curve tracer).



Link to video of curves using a potentiometer to vary the amount of feedback
Attached Images
File Type: jpg NTE451 Parallel Feedback Curves.JPG (118.2 KB, 180 views)
File Type: jpg NTE451 Parallel Feedback Curves-001.JPG (127.3 KB, 173 views)
File Type: jpg NTE451 Parallel Feedback Curves-002.JPG (125.9 KB, 176 views)
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Old 7th November 2012, 05:18 PM   #30
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A BJT

The JFET curves look more like a real triode. The BJT looks extremely linear though.
Attached Images
File Type: jpg BJT Parallel Feedback.jpg (171.9 KB, 173 views)

Last edited by avincenty; 7th November 2012 at 05:20 PM. Reason: added comment
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