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

Tubelab Discussion and support of Tubelab products, prototypes and experiments

Reply
 
Thread Tools Search this Thread
Old 17th September 2020, 10:03 AM   #741
rock12 is offline rock12  United States
diyAudio Member
 
Join Date: Nov 2010
Location: midland mi
Is it ok to use carbon film resistors
  Reply With Quote
Old 22nd September 2020, 08:09 AM   #742
itsikhefez is offline itsikhefez  United States
diyAudio Member
 
Join Date: Aug 2015
Tubelab Simple P-P
Carbon film is probably fine in most positions.. theoretically the circuit will be quieter with metal film.

George, hoping to get your thoughts on the compensation cap value.
I've tried 120pF, 270pF, 390pF and 470pF.
As you increase the value, the square wave gets nicer.

The issue though is that beyond 120pF, the amp distorts at about 3W of output.
I think this could be similar to an issue rkinze mentioned with new 12AT7's, although I've tried 3 different NOS types, a Siemens & Halski, Brimar and GE 6201 and all of them have the same issue.
I've also tried various output tubes JJ and NOS types, as well as both UL and Pentode connection, with the issue the same.

Technically, I can keep the amp with 120pF as I can drive the amp to clipping without observing this distortion, but the square wave is pretty ugly.
Attached Images
File Type: jpg 2020-09-17 20.28.13.jpg (159.9 KB, 121 views)
  Reply With Quote
Old 13th October 2020, 07:07 AM   #743
itsikhefez is offline itsikhefez  United States
diyAudio Member
 
Join Date: Aug 2015
Tubelab Simple P-P
I still have the instability issue as demonstrated above.
I have a different thread with more detailed information, the latest in this post: EL84 measurable distortion between different makes

If anyone has an idea of where to start looking, please let me know.
Thanks!!
  Reply With Quote
Old 17th October 2020, 09:09 PM   #744
itsikhefez is offline itsikhefez  United States
diyAudio Member
 
Join Date: Aug 2015
Tubelab Simple P-P
If I'm not using a pot, can I replace the 220K resistors across the input to something like 50K ?
  Reply to this post

Reply


Tubelab Simple P-PHide 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

Similar Threads
Thread Thread Starter Forum Replies Last Post
Electrolyticless Tubelab Simple SE nic6paul Tubelab 26 20th August 2013 12:56 PM
Second Tubelab Simple SE board done budmaestro Tubelab 0 24th July 2008 12:18 AM
First Project Finished-Tubelab Simple SE waam68 Tubelab 2 12th April 2008 06:23 AM
Tubelab Simple SE & Edcor waam68 Tubelab 2 6th March 2008 12:15 PM
New SET: JE labs simple 45 or tubelab SE? cwujek Tubelab 14 27th November 2007 04:15 AM


New To Site? Need Help?

All times are GMT. The time now is 12:09 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright ©1999-2020 diyAudio
Wiki