John Curl's Blowtorch preamplifier part II - Page 452 - 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 2nd June 2010, 05:54 PM   #4511
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
I was referring to the original Dyna phono stage and the corresponding Audible Illusions 6DJ8 version of essentially the same circuit.
  Reply With Quote
Old 2nd June 2010, 10:36 PM   #4512
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
I would like to make the comment that vacuum tubes, while very good, are not what I design with. The 12AX7 has been very successful over the decades, BUT it is limited, especially in current drive, which can be VERY important in some situations.
Let us go on about solid state solutions, and leave the tubes to another thread.
  Reply With Quote
Old 2nd June 2010, 10:59 PM   #4513
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally Posted by john curl View Post
Let us go on about solid state solutions
Boooooo! Booooooooooo!
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 3rd June 2010, 01:45 AM   #4514
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Please stick with your own threads, SY. There are plenty of threads for discussing vacuum tube solutions. However, threads concerning solid state solutions at a professional level are relatively few.
  Reply With Quote
Old 3rd June 2010, 02:17 AM   #4515
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
My apologies. I thought you were interested in high performance design, not just restricting yourself to familiar and comfortable solutions. You're certainly welcome to continue discussing cheaper and easier compromises without me interfering.
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 3rd June 2010, 02:53 AM   #4516
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
Silicon circuits, even with the latest generation of OPamps can be made to sound extremely well. When it comes to measurements it is hard to make a tube stage that has as low distortion, noise and very high bandwidth. Using discrete circuits with relatively high voltage it gets quite thin for tubes. I can see no cheap and easy compromises provided the circuit is competent and build with good parts. I whould say that it is cheaper and easiers to make a good sounding tube circuit. I know what i am talking about because i had a lot of tube amps at home with aspiration to be "The Best". I listened at length to them and i measured them as good as i could. Except a portion of harmless second harmonic and a different noise profile i could not find any magical properties in them. For me it is just another technological option. A lot what a tube can do sonically can be mimicked with single ended Fet circuit and i got particular good in building buffers that add whatever distortion and noise i like. Actually i think a lot what makes a tube sound good is adding some ( small ) extremely attractive distortion to the music. But now i am back where i should not be here.
  Reply With Quote
Old 3rd June 2010, 03:56 AM   #4517
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Joachim, I do not think that any IC op amps do as well as a well designed piece of tube equipment, OR good discrete solid state electronics.
As far as IC's are concerned, today I tried your suggestion of National OP AMP as replacement for the AD797, which is very good, but too expensive, in my opinion, compared to its competition. It works fine, sounds good, and I did not measure anything higher than 3'rd harmonic. Perhaps this IS progress in IC's, I hope so.
My problem with vacuum tubes is the related coupling to and from it, that means lots of caps, and or transformers. It is these components that I worry most about.
  Reply With Quote
Old 3rd June 2010, 04:10 AM   #4518
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
Allan Wright and i listened in my place to his top Tube Stage compared to one of my OPamp based preamp. Ask him. I do discrete too when i try to make the best posible but this little preamp is a lot of fun. The MC input stage in that Pramp is an INA build from two LME49990 and one ADA4627 per channel. A conventional feedback structure with the LME49990 brings not the best sound out of it. I tryed virtually everything, series feedback, shunt feedback, differential etc. and the INA topology works by far the best soundwise. I can not measure distortion in that circuit at cruising level. It is below the noise.
  Reply With Quote
Old 3rd June 2010, 04:18 AM   #4519
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
Here come some measurements. This is the resolution floor of my analyser.
Attached Images
File Type: jpg Generator Noise and Distortion.jpg (99.6 KB, 192 views)
  Reply With Quote
Old 3rd June 2010, 04:21 AM   #4520
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
Here come the measurements from an early prototype that used 2 x AD797 and one OPA827. The new version is better. I can reduce noise by 6dB with paralleling of input opamps but then it gets expensive again so discrete whould be more economical.
Attached Images
File Type: jpg Goldstandart -40dB INA.jpg (116.7 KB, 183 views)
File Type: jpg Goldstandart -30dB INA.jpg (118.1 KB, 179 views)
File Type: jpg Goldstandart -20dB INA.jpg (118.1 KB, 180 views)
  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 06:11 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