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 10th July 2018, 06:15 PM   #41
jfetter is offline jfetter  United States
diyAudio Member
 
jfetter's Avatar
 
Join Date: Jun 2012
Location: North Houston
Sebastian,
I've been on some other projects but now back on it, reviewed everything up to this point for errors oversights and found none.
So be patient , have you tested anything like this before?
(Note: The 1k grid resistor also limits forward grid current in addition to kill oscillation if any tendencies )
Regards
Bruce
__________________
“A grounded grid is a happy grid”. jfetter
  Reply With Quote
Old 15th July 2018, 06:33 PM   #42
jfetter is offline jfetter  United States
diyAudio Member
 
jfetter's Avatar
 
Join Date: Jun 2012
Location: North Houston
Default 6DJ8 Unity gain non inverting

Trying to get back into it. I had a 6DJ8 and thought the specs looked interesting so here is a series of tests. This group is unity non inverting.
The readme file has hardware info. The circuit is identical to the one Sebastian drew but a 6DJ8 is used.

Interesting that I attempted this time to use one of those low cost switchers on ebay for 6VDC heater. They are verrrry noisy!

Went back to my low noise dc supply. Its a switcher but has special filters for for use with sensitive radio receivers.

My test board is not yet assembled so these two test runs are on perf board.

The readme file has hardware info.

-
Attached Images
File Type: jpg 6DJ8.jpg (656.1 KB, 303 views)
File Type: png fft1000.png (10.0 KB, 302 views)
File Type: png fft2500.png (14.4 KB, 293 views)
File Type: png fft10000.png (7.5 KB, 287 views)
File Type: png fsweep.png (4.8 KB, 282 views)
File Type: png thd.png (6.4 KB, 32 views)
Attached Files
File Type: txt readme.txt (253 Bytes, 8 views)
__________________
“A grounded grid is a happy grid”. jfetter
  Reply With Quote
Old 15th July 2018, 06:39 PM   #43
jfetter is offline jfetter  United States
diyAudio Member
 
jfetter's Avatar
 
Join Date: Jun 2012
Location: North Houston
Here are tests using inverting gain of 4.7

Note the sight increase in thd is mostly 2nd.

Still remaining are test board assembly, CC diode spreadsheet, PCB fab using new CAD (dropped Eagle) and same project but repeated using grounded grid topology.

-
Attached Images
File Type: png fft1000.png (11.4 KB, 28 views)
File Type: png fft2500.png (9.0 KB, 15 views)
File Type: png fft10000.png (7.8 KB, 15 views)
File Type: png response.png (5.2 KB, 15 views)
File Type: png thd.png (6.1 KB, 11 views)
Attached Files
File Type: txt readme.txt (308 Bytes, 6 views)
__________________
“A grounded grid is a happy grid”. jfetter
  Reply With Quote
Old 15th July 2018, 11:32 PM   #44
jfetter is offline jfetter  United States
diyAudio Member
 
jfetter's Avatar
 
Join Date: Jun 2012
Location: North Houston
I ordered some for evaluation.
(automotive group)
OPA1612AQDRQ1 soic only

will receive conduction heat due to physical close quarters.

High temperature operation 85c , functional to 125C.
Hi drive similar to ne5532 plus swings closer to rail.
Power / distortion and bandwidth improved.
Expensive $$ about 7.00 but it's worth it.

OPA1612-Q1 Application notes,More literatur, Blogs
__________________
“A grounded grid is a happy grid”. jfetter
  Reply With Quote
Old 18th July 2018, 03:27 AM   #45
jfetter is offline jfetter  United States
diyAudio Member
 
jfetter's Avatar
 
Join Date: Jun 2012
Location: North Houston
One more note: My ur22mkii indicates .0015% thd looping back to itself.
So as tested on the two circuits .001% was added with the unity gain and .0015 with inv gain configuration.
As I mentioned earlier not really going for lowest thd but rather good sound.
__________________
“A grounded grid is a happy grid”. jfetter
  Reply With Quote
Old 18th July 2018, 07:41 PM   #46
jfetter is offline jfetter  United States
diyAudio Member
 
jfetter's Avatar
 
Join Date: Jun 2012
Location: North Houston
This pic shows general idea, if possible to make pcb dual use.

Stuff with the single opamp package and miniature triode tube footprint for 990 package.

Or stuff with dual opamp package and 9 pin dual triode with dip8 male header.
May have to use 4 layer board but that's better anyway for thermals.
Attached Images
File Type: jpg WP_20180718_14_18_00_Pro (2).jpg (520.4 KB, 58 views)
__________________
“A grounded grid is a happy grid”. jfetter
  Reply With Quote
Old 23rd July 2018, 01:50 AM   #47
jfetter is offline jfetter  United States
diyAudio Member
 
jfetter's Avatar
 
Join Date: Jun 2012
Location: North Houston
Received the op amps and fresh tubes.

-
Attached Images
File Type: jpg WP_20180722_20_37_34_Pro.jpg (596.0 KB, 60 views)
__________________
“A grounded grid is a happy grid”. jfetter
  Reply With Quote
Old 26th July 2018, 12:41 AM   #48
jfetter is offline jfetter  United States
diyAudio Member
 
jfetter's Avatar
 
Join Date: Jun 2012
Location: North Houston
Here is pic of schematic and ratsnest. No doubt there will be many changes before going to fab. Board is 1" X 1".
Note the ne5532 is called out but its actually an OPA1612AQDRQ1.

-attached
Attached Images
File Type: png sch.PNG (49.9 KB, 93 views)
File Type: png ratnest-bd.PNG (77.5 KB, 90 views)
__________________
“A grounded grid is a happy grid”. jfetter
  Reply With Quote
Old 31st July 2018, 05:34 AM   #49
Obisix is offline Obisix  Hungary
diyAudio Member
 
Join Date: Mar 2015
Location: Budapest
nice jfetter!

What is the part called E452? I googled it and found nothing
__________________
Sebastian Bak
  Reply With Quote
Old 31st July 2018, 04:22 PM   #50
PRR is offline PRR  United States
diyAudio Member
 
PRR's Avatar
 
Join Date: Jun 2003
Location: Maine USA
> What is the part called E452?

See post #35.
  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 02:08 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki