Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

DOA - Discrete Op Amps
DOA - Discrete Op Amps
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 12th March 2018, 09:07 PM   #1
jfetter is offline jfetter  Costa Rica
diyAudio Member
 
jfetter's Avatar
 
Join Date: Jun 2012
Location: na
Default Composite Tube-Opamp dual Dip8

well itís official, i have the doa bug.
iím doing it with a classic opamp mounted/combined with sub miniature triode.

Edit 10-2018 : I've learned a great deal during this project and now taking that knowledge to the next level.
So there will be no more updates from me on this fantastic concept. Thanks to Brent Butler for publishing it in 1998.
-Bruce

Last edited by jfetter; 5th October 2018 at 02:05 PM. Reason: title edit and closure
  Reply With Quote
Old 15th March 2018, 02:01 PM   #2
Charles Darwin is offline Charles Darwin  United Kingdom
diyAudio Member
 
Join Date: Nov 2009
Location: Birmingham, UK
Dead On Arrival?
  Reply With Quote
Old 15th March 2018, 02:03 PM   #3
TheGimp is offline TheGimp  United States
diyAudio Member
 
TheGimp's Avatar
 
Join Date: Aug 2009
Location: Johnson City, TN
"Dead Bug", IC mounted upside down?
__________________
If there are no dogs in Heaven, I don't want to go there.
  Reply With Quote
Old 15th March 2018, 10:41 PM   #4
jfetter is offline jfetter  Costa Rica
diyAudio Member
 
jfetter's Avatar
 
Join Date: Jun 2012
Location: na
ha yes ‘discrete op amps’, so far been fun.
doing a semi-discrete 8 pin dip using opa445 with sub minature triode.
Testing looks great. the heater will of course have off-chip supply.
  Reply With Quote
Old 18th March 2018, 04:27 PM   #5
Monte McGuire is online now Monte McGuire
diyAudio Member
 
Join Date: Jul 2013
DOA - Discrete Op Amps
I'd call that a composite amplifier, which I think is actually a wiser idea than to insist on 'discrete only', a true DOA. There are some things, like current sources and mirrors, thermal coupling, and close device matching, that are much easier to do with monolithic ICs than with a purely discrete amplifier. That's generally how 'design purity mandates' often work with engineering - religious purity often compromises the design and performance.

I too always think of 'dead on arrival' when I see DOA. Must be a generational thing!

Have fun!
  Reply With Quote
Old 18th March 2018, 05:39 PM   #6
leadbelly is online now leadbelly  Canada
diyAudio Member
 
leadbelly's Avatar
 
Join Date: Dec 2002
Location: Calgary, Alberta
If there's anything that screams discrete opamp, it surely must be an 8 pin opamp + triode...

WTF is this thread supposed to be about?
__________________
Wise men speak because they have something to say; Fools because they have to say something. Plato
  Reply With Quote
Old 18th March 2018, 07:35 PM   #7
jfetter is offline jfetter  Costa Rica
diyAudio Member
 
jfetter's Avatar
 
Join Date: Jun 2012
Location: na
this is a pic of working ckt. its not yet stacked for dip plugin.
The output is classA from tube but the opa445 is servo.
Attached Images
File Type: jpeg 42D8A73F-58CA-467C-900A-5CBEB4640ED0.jpeg (630.4 KB, 1497 views)
  Reply With Quote
Old 18th March 2018, 07:48 PM   #8
jfetter is offline jfetter  Costa Rica
diyAudio Member
 
jfetter's Avatar
 
Join Date: Jun 2012
Location: na
sorry here is some data from earlier testing with ne5532
Attached Images
File Type: png BCBEF4DD-5F6C-4981-B996-705FA23E77FC.png (11.3 KB, 1452 views)
File Type: jpeg 6C57F46F-78E4-40FD-A253-3E856C5F44EB.jpeg (19.2 KB, 1418 views)
  Reply With Quote
Old 20th March 2018, 05:36 PM   #9
jfetter is offline jfetter  Costa Rica
diyAudio Member
 
jfetter's Avatar
 
Join Date: Jun 2012
Location: na
I must be doing something wrong, have tested numerous fet input parts and they all are very difficult to stabilize. distortion always increases with frequency but the ne5532 requires no compensation , verrry low dist across audio spectrum too at least in topologies i’ve tested so far. the fets need inner and outer loop compensation and would i’m sure smear upper register music.
say it ain’t so please
  Reply With Quote
Old 20th March 2018, 05:50 PM   #10
Monte McGuire is online now Monte McGuire
diyAudio Member
 
Join Date: Jul 2013
DOA - Discrete Op Amps
Quote:
Originally Posted by jfetter View Post
sorry here is some data from earlier testing with ne5532
Nice curves, but is there a way to do an average of those waterfall curves, and not a waterfall? There's no time or decay component, so the extra time dimension isn't as useful as is taking the average of all of those curves. That will help you to resolve low level details better and provide less error on what you measure. Not certain if that software is up to it, but a friendly suggestion nonetheless!
  Reply With Quote

Reply


DOA - Discrete Op AmpsHide 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

Forum Jump


New To Site? Need Help?

All times are GMT. The time now is 04:30 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki