John Curl's Blowtorch preamplifier part II - Page 3140 - 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 13th December 2012, 07:07 PM   #31391
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by RNMarsh View Post
And, if you dont rely primarily on gnfb to make the thing linear as possible, the good complimentary jFEts issue subsides and can be made to work very well with more local degeneration and modest gnfb used for excellent results. This was my thought and implimentation of desired complimentary jFET topologies for line level amps. - Thx RNMarsh
These are all fashion design principles common to a narrow body of audio designers.
__________________
Silence is so accurate.
  Reply With Quote
Old 13th December 2012, 07:20 PM   #31392
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
For that's audio design, not instrumentation design.
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html
  Reply With Quote
Old 13th December 2012, 07:32 PM   #31393
wayne is offline wayne  United States
diyAudio Member
 
Join Date: Jan 2002
Location: Northern California
Quote:
Originally Posted by scott wurcer View Post
These are all fashion design principles common to a narrow body of audio designers.
Man jewelry as I call it. But it lets me buy my preferred forms of man jewelry.
  Reply With Quote
Old 13th December 2012, 07:36 PM   #31394
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by PMA View Post
For that's audio design, not instrumentation design.

Modest gnfb? not for instruments either.
__________________
Silence is so accurate.
  Reply With Quote
Old 13th December 2012, 07:37 PM   #31395
diyAudio Member
 
Esperado's Avatar
 
Join Date: Jul 2011
Location: France
Quote:
Originally Posted by Waly View Post
You seem to assume that complementary JFETs are the one and only option for what you call "high end". Is this correct, or is this just another excuse to avoid (good) opamps?
I believe J.C. have never tried a "GOOD" modern OPA, and when we read his comment, we just have to replace "OPA" by "µ471".
The main thing is OPAs are not fashionable, and not good for guru designers to sell mystery.
I wonder where can be evil class B, when measured distortion can be < -100 dB @ 100 kHz
__________________
Ultimate Protection and more.The Only Source of Knowledge is experience, everything else is just information” ©A. Einstein

Last edited by Esperado; 13th December 2012 at 07:44 PM.
  Reply With Quote
Old 13th December 2012, 07:55 PM   #31396
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
I have 100's of IC's in my office, and samples of just about everything that I can find useful for audio. I have been using and testing IC's since 1966, a long time ago. In 1969, I used uA741's for servo design, wonderful devices for that.
In 1970 I used the Harris HA911 in a studio board, with the slew rate of +5/-2.5V/us and +/- 24V operation. This was my FIRST failure and I tend to believe that the IC's were part of the reason for the failure. The ceramic caps were the second reason.
Mark Levinson used IC's FIRST in the LNP-2 preamp, hand selected by Dick Burwen for audio quality, in advance. This is when first I saw the XOVER DISTORTION in many of the samples of the HA-911. Mark's use of the selected HA-911 worked pretty well, BUT ultimately he had me design a discrete replacement for it. After 1975 or so, all LNP-2 and LNC-2 products use my discrete 'upgrade'.

Last edited by john curl; 13th December 2012 at 08:04 PM.
  Reply With Quote
Old 13th December 2012, 08:07 PM   #31397
diyAudio Member
 
Esperado's Avatar
 
Join Date: Jul 2011
Location: France
Despite what i read everywhere, on my experience, slew rate is one of the most important thing to care of when we chose an OPA for audio.
20V/µs is far to be enough, and more it is, more transparent is the device.
Slew rate can be > 1000V/µs, Noise can be as low as 1.5nV/√Hz, output current >150ma, distortion so low that it is not a concern.
Of course, implementation is important, and, often, in a high end system, you cannot replace one specific OPA by an other. Need to tune the value of the feedback resistance, parallel cap for no overshoot etc...
And, of course, great care of power supply and HF decoupling.
Looking for a perfect sample can be time consuming, there are so many available devices, and there is often one of your requisite you have to sacrifice.
__________________
Ultimate Protection and more.The Only Source of Knowledge is experience, everything else is just information” ©A. Einstein
  Reply With Quote
Old 13th December 2012, 08:07 PM   #31398
diyAudio Member
 
jneutron's Avatar
 
Join Date: Jan 2004
Location: away
Quote:
Originally Posted by PMA View Post
Still not good enough. Regarding JFETs, no good P-parts available.
Closest I found.

CentralSemi.com

ya gotta love them astericks.

jn
  Reply With Quote
Old 13th December 2012, 08:16 PM   #31399
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
So what, Esperado? What makes YOUR OPINION any better than MY opinion? I might agree with you that high slew rate is important, but maybe not 1000V/us for a preamp. Seems a little excessive, when 5V/us is considered OK in every test, EXCEPT FOR FM DISTORTION, that we have made with real audio signals.
  Reply With Quote
Old 13th December 2012, 08:39 PM   #31400
diyAudio Member
 
Esperado's Avatar
 
Join Date: Jul 2011
Location: France
Quote:
Originally Posted by john curl View Post
So what, Esperado? What makes YOUR OPINION any better than MY opinion?
The fact that i'm not in concern with the sell of anything ? You share your opinion, when i don't agree, i share mine. Am-i not allowed ?
Anyway, i believe generalizations like "OPA not good for audio" are obviously suspect, like all generalizations.

I use to compare my preamp circuits with strait wires. When i'm not able to hear a real difference, i believe i do not have to worry anymore. And , as i said previously, i achieved that many time with various OPAs. Funny, never with OPA rated for audio.
__________________
Ultimate Protection and more.The Only Source of Knowledge is experience, everything else is just information” ©A. Einstein

Last edited by Esperado; 13th December 2012 at 09:01 PM.
  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 10:49 AM.


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