John Curl's Blowtorch preamplifier part II - Page 2216 - diyAudio
Go Back   Home > Forums > Member Areas > The Lounge

The Lounge A place to talk about almost anything but politics and religion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 10th April 2012, 07:56 PM   #22151
diyAudio Member
 
Join Date: Nov 2011
Quote:
Originally Posted by gk7 View Post
Yes, they seem to be the same.
Thank you, gk7. So we're back in 1978.

Servus,
  Reply With Quote
Old 11th April 2012, 12:13 AM   #22152
diyAudio Member
 
johnferrier's Avatar
 
Join Date: Sep 2003
Location: WA
Curl's Law: Moore is Less ?

Click the image to open in full size.


.
__________________
Michael Gazzaniga - "The arts are not frosting but baking soda."
  Reply With Quote
Old 11th April 2012, 01:08 AM   #22153
diyAudio Member
 
Speedskater's Avatar
 
Join Date: Sep 2002
Location: Lakewood, Ohio
Quote:
Originally Posted by wayne View Post
John you kicked butt on page 48 of the new Absolute sound for best preamps ever.(May/June)
But there is a picture of some kid pretending to be John.
__________________
Kevin
  Reply With Quote
Old 11th April 2012, 04:27 PM   #22154
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Well, the 'chatter' has decreased, so maybe we can get something done.
What PMA has brought up and emulated (far better than I ever could) is the basic topology that is used by the Blowtorch preamplifier, which in turn, was a adaption of Charles Hansen's Ayre topologies, and inspired by the 'less is best' tube line stage developed by Art Ferris.
Now, many here will wonder why I might give so much credit to others for something that I am known for, namely balanced comp-differential fet designs. Well, my last design effort of major proportions stopped after Vendetta Research closed shop in 1992.
And at that time, I worked part time for Audible Illusions as a consultant, so I got to work with tube products for a period of time. Also, did some extra measurement of the open loop line stage that Art Ferris developed, using a parallel version of a single tube.
When I made the extended distortion measurement, more than 20 years ago, I used a wave analyzer on the distortion residue of an HP339 HD Analyzer, while measuring the line stage at some 'reasonable' output. I found very little, but 2'nd harmonic, maybe a little 3'rd, but nothing else within my measurement limit, at the time, which was perhaps -120dB down. I was impressed! NO single solid state device, running open loop, could match that. It seemed that that tube topology could not be copied with any real success in a solid state product. Perhaps, it is best to try a more sophisticated topology, WITH ESSENTIALLY THE SAME THRU-PATH, in order to get similar subjective results.
The first option, of course is the differential pair. The second option is the complementary differential fet quad, with AC coupling with 4 output caps, 2 summing for + out and 2 summing for - out.
The third option was to use the folded complementary differential cascode, much like Charles Hansen uses with his designs, to remove the output caps and the resistor loading distortion generation from having to use load resistors with a relatively low voltage power supply voltage for practical reasons.
This we tried, and this we succeeded in.
Of course, there were a hundred other problems and design decisions that had to be made, but in principle, we had a direct coupled in-out, open loop, differential or single ended in or out, so a selection of balanced and unbalanced configurations could be easily used. Our thru-path was at minimum, one comp cascode to an output, worst case was a differential fet pair and cascode to an output. About as minimum as I can get, and still get reasonably low distortion, open loop.
Superficially, there appears to be little difference between the JC-80 of 30 years ago, and the Blowtorch, but there are many significant changes in the 15-20 years that occurred between the original inception of these 'all out' designs. They are just more subtle to most people.
A good example of this is the 'cloning' of the JC-80 that has 2 threads here at this time.
It is a bit like trying to make a kit car into a Porsche. It can be done, but not consistently. Enough for now.

Last edited by john curl; 11th April 2012 at 04:41 PM.
  Reply With Quote
Old 11th April 2012, 04:39 PM   #22155
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
A Blowtorch schematic outline, courtesy PMA.
Attached Images
File Type: png circuit.PNG (19.0 KB, 390 views)
  Reply With Quote
Old 11th April 2012, 06:11 PM   #22156
diyAudio Member
 
Join Date: May 2005
Location: toronto
While the input stage is high idss Toshiba 2SK/2SJ unobtanium duals, what type of outputs do you prefer ? Fairchild? Toshiba? Why - device capacitance or linearity?

Last edited by ticknpop; 11th April 2012 at 06:25 PM.
  Reply With Quote
Old 11th April 2012, 06:14 PM   #22157
Waly is offline Waly  United Kingdom
diyAudio Member
 
Waly's Avatar
 
Join Date: Jan 2011
Location: London
Quote:
Originally Posted by john curl View Post
A Blowtorch schematic outline, courtesy PMA.
Wow, so indeed, for quite some time, this guy correctly guessed the Blowtorch core schematic:

Uskok preamplifier

The author seem to be a member on this forum http://www.diyaudio.com/forums/members/moamps.html so it would be interesting to hear some comments about...
  Reply With Quote
Old 11th April 2012, 07:31 PM   #22158
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Talk about a clone, this preamp takes the cake! Too many similarities, and a few mistakes. I NEVER completely discussed the CTC Blowtorch schematic and the way that I do things, so without taking one apart, one could not possibly get every detail the same, but that's OK. This Russian preamp looks to be pretty good, better than most.
Why I am attacked for claiming ownership of certain ideas that I have worked with for decades, usually before anyone else seems to have done so, is beyond me.
The designer's final attack on me, was a bit 'below the belt'. As has been stated here, most of my circuit topology ideas have arisen between 10 and 45 years ago, so schematics get lost, get burned in a firestorm, or are deliberately kept away from competition, over the decades. The last time I openly discussed something 'important' to me with a competitor, I found that they had taken my design, almost part for part, much like this Russian preamp has done. They just took it from my patent, and they laughed at me when I protested. And so it goes.
  Reply With Quote
Old 11th April 2012, 08:10 PM   #22159
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Serbian or Croatian, I would guess.
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html

Last edited by PMA; 11th April 2012 at 08:14 PM.
  Reply With Quote
Old 11th April 2012, 08:35 PM   #22160
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Sorry, I can't tell the difference at first glance.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 11:32 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2