Discrete Opamp Open Design - Page 300 - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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 31st October 2013, 06:42 PM   #2991
diyAudio Member
 
Join Date: Sep 2007
Send a message via Yahoo to linuxguru
Quote:
Originally Posted by rsavas View Post
I have BF862 is my stock. Have you looked at KSC1845/KSA992 and the smt versions fjv992/1845?
Thanks, I'll PM you later regarding the BF862. I've used the original NEC 2sc1845/a992 extensively, but had no idea until now about the Fairchild SMD versions - will check them out.
  Reply With Quote
Old 31st October 2013, 10:40 PM   #2992
diyAudio Member
 
Join Date: Sep 2007
Send a message via Yahoo to linuxguru
This is a simulation schematic of a simplified 4-BJT Ken's Diamond as the output stage - it's derived from the 6-BJT Ken's Diamond, but the CFPs at the output have been reduced to single BJTs, thus reducing the BJTs in the output stage to 4. The voltage reference has also been opportunistically obtained from the VAS CCS without any additional device.

It seems to simulate with a few dB lower H3 than the Diamond Cascode at similar output stage bias of around 8 mA. It still needs further analysis of stability, phase margin, overdrive and clipping behaviour, PSRR, etc., but it looks to be a viable contender for a Class-A output stage for the FET990.
Attached Images
File Type: jpg lf06s_v1.4_kens_dmd_simple.jpg (96.7 KB, 750 views)
File Type: jpg lf06s_v1.4_kens_dmd_simple_4v600r_fft.jpg (84.1 KB, 733 views)
Attached Files
File Type: asc lf06s_v1.4_kens_dmd_simple.asc (9.0 KB, 17 views)
  Reply With Quote
Old 1st November 2013, 07:01 AM   #2993
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Demian and I both live in Northern California and have worked with and known each other for many years.... we can measure just about anything. We would be happy to see what difference there might be between your SIM VFA and an actual built unit.

Thx-RNMarsh
  Reply With Quote
Old 7th November 2013, 05:31 PM   #2994
diyAudio Member
 
grhughes's Avatar
 
Join Date: Mar 2005
Location: Cubicle Sweet Cubicle, Springfield, Missouri, USA
Has anyone built a Wurcer preamp with real parts and tested it on a bench? Thank you? Ray
__________________
" "The fool doth think he is wise, but the wise man knows himself to be nothing but a fool." Will Shakespeare
  Reply With Quote
Old 7th November 2013, 05:44 PM   #2995
diyAudio Member
 
grhughes's Avatar
 
Join Date: Mar 2005
Location: Cubicle Sweet Cubicle, Springfield, Missouri, USA
I've laid out a board with to92 thru hole parts but I have some questions. Do the input jfets require shielding around the gate pads? Some jfet input opamps require this. Also are catching diodes on the output necessary as part of the diamond compensation. They are not on any of Scott's schematics but appears on others. Also moving the offset null to the resistor leads of the positive current source requires many more parts than putting it where Scott originally had it. Just the things I'm wrestling with. Thanks Ray
__________________
" "The fool doth think he is wise, but the wise man knows himself to be nothing but a fool." Will Shakespeare
  Reply With Quote
Old 7th November 2013, 05:56 PM   #2996
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Hi Ray,

This was designed by SW and so should use his schematic and his Ok on any changes or additions (like diodes on output). Others' mods/changes to it can have the others' pcb made. I would like to use the design exactly as Scott created it. Then others designs can have their pcb for it made.

The ring around the inputs (jFETs) is a good idea so we can try using it as a guard ring.

Thx--- I have been waiting a long time for the thru-hole version. :-)


-RNMarsh

Last edited by RNMarsh; 7th November 2013 at 05:58 PM.
  Reply With Quote
Old 7th November 2013, 06:09 PM   #2997
diyAudio Member
 
grhughes's Avatar
 
Join Date: Mar 2005
Location: Cubicle Sweet Cubicle, Springfield, Missouri, USA
Thanks Richard. I've used Scott's two board sandwich idea and his schematics only. I haven't transferred it from the initial drawing to the computer. Just mulling around options. Ray
__________________
" "The fool doth think he is wise, but the wise man knows himself to be nothing but a fool." Will Shakespeare
  Reply With Quote
Old 17th December 2013, 03:03 AM   #2998
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Quote:
Originally Posted by grhughes View Post
Thanks Richard. I've used Scott's two board sandwich idea and his schematics only. I haven't transferred it from the initial drawing to the computer. Just mulling around options. Ray
Where is everything now? Its been awhile.

Thx-RNMarsh
  Reply With Quote
Old 17th December 2013, 03:19 AM   #2999
diyAudio Member
 
grhughes's Avatar
 
Join Date: Mar 2005
Location: Cubicle Sweet Cubicle, Springfield, Missouri, USA
Hi! I have it laid out. I'm trying to reduce trace size on summing points by moving around some parts. It's 2 inches by 1.5 inches. I'll transfer it to computer as soon as my newly ordered software comes. My current software needs upgrading and crashes. I would like your opinion. Ray
__________________
" "The fool doth think he is wise, but the wise man knows himself to be nothing but a fool." Will Shakespeare
  Reply With Quote
Old 17th December 2013, 03:32 AM   #3000
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
OK.

and - I am ready to measure a working SWOPA when ever... .

Thx-RNMarsh
  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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Discrete OPAMP audio-gd Vendor's Bazaar 27 20th September 2012 05:02 PM
discrete opamp help blackpowderaudio Parts 0 16th December 2009 04:46 PM
THAT transistor headphone amp (250ma discrete opamp) design sanity check. Russ White Headphone Systems 19 13th December 2007 01:52 PM


New To Site? Need Help?

All times are GMT. The time now is 10:15 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