EL34 pentode output in SSE - diyAudio
Go Back   Home > Forums > Commercial Sector > Vendor Forums > Tubelab

Tubelab Discussion and support of Tubelab products, prototypes and experiments

Reply
 
Thread Tools Search this Thread
Old 29th August 2011, 11:09 AM   #1
Skorpio is offline Skorpio  Denmark
diyAudio Member
 
Join Date: Mar 2004
Location: Denmark
Default EL34 pentode output in SSE

I am currently running my SSE with EL34 in triode connection. This is a very nice amp with approx. 5W output...

I have no UL connection on the OT and reading about Pentode connection of EL34 shown that this would be a step down in performance?

Therefore I was thinking of the possibility to use some feedback (like in Baby Huey) to lower the output impedance of the Pentode...is that a possible way to go?

What will be the penalty, besiden the need for more drive?
  Reply With Quote
Old 29th August 2011, 12:54 PM   #2
Skorpio is offline Skorpio  Denmark
diyAudio Member
 
Join Date: Mar 2004
Location: Denmark
Here are an interesting alternative..."screen drive":

Screen Driven, DC Coupled, Single-ended EL509 Amp
  Reply With Quote
Old 29th August 2011, 03:12 PM   #3
rknize is offline rknize  United States
diyAudio Member
 
rknize's Avatar
 
Join Date: Feb 2009
Location: Chicagoland
Send a message via AIM to rknize Send a message via Yahoo to rknize
Why not use the local, cathode feedback feature also supported by the SSE? That will clean up the pentode operation for you.
  Reply With Quote
Old 29th August 2011, 03:27 PM   #4
Skorpio is offline Skorpio  Denmark
diyAudio Member
 
Join Date: Mar 2004
Location: Denmark
Yes, that seems to be a good idea, do you know what power to expect in pentode mode?
  Reply With Quote
Old 29th August 2011, 03:49 PM   #5
rknize is offline rknize  United States
diyAudio Member
 
rknize's Avatar
 
Join Date: Feb 2009
Location: Chicagoland
Send a message via AIM to rknize Send a message via Yahoo to rknize
Expect around 10W with the EL34. Up to 14W is possible with a bigger tube, like KT88.
  Reply With Quote
Old 29th August 2011, 04:36 PM   #6
w5jag is offline w5jag  United States
diyAudio Member
 
Join Date: Feb 2007
Location: Arkansas
Quote:
Originally Posted by rknize View Post
Why not use the local, cathode feedback feature also supported by the SSE? That will clean up the pentode operation for you.
I'm using Hammond 125ESE transformers on my SSE and, imo, cathode feedback by itself does little to tame pentode shrillness on the SSE, although it works great for linearizing (sp?) output transformers.

An additional local plate to grid (Schade) negative feedback loop has worked well for me on the SSE in pentode mode, and is easy to implement, but Schade feedback is not without its critics.

There is more of a discussion on the Schade feedback in the SSE in the 6146 SSE thread, three or four pages into it.

Win W5JAG
  Reply With Quote
Old 29th August 2011, 06:00 PM   #7
rknize is offline rknize  United States
diyAudio Member
 
rknize's Avatar
 
Join Date: Feb 2009
Location: Chicagoland
Send a message via AIM to rknize Send a message via Yahoo to rknize
It's a different sound for sure. Not necessarily bad...just depends on your speakers and your tastes.
  Reply With Quote
Old 30th August 2011, 09:46 AM   #8
Skorpio is offline Skorpio  Denmark
diyAudio Member
 
Join Date: Mar 2004
Location: Denmark
Thank you for your inputs!

I will look into the thread...

Do you have more detailed info about the difference in sound? What are the pros and cons....I am thinking on both Pentode/cathode feedback and pentode/Schade feedback versus a clean triode...?
  Reply With Quote
Old 30th August 2011, 04:33 PM   #9
rknize is offline rknize  United States
diyAudio Member
 
rknize's Avatar
 
Join Date: Feb 2009
Location: Chicagoland
Send a message via AIM to rknize Send a message via Yahoo to rknize
How it sounds to you on your speakers is going to be different than how it sounds on mine. I have switches for triode/UL mode, cathode feedback, and even SS vs tube rectification. I also have a rotary switch that allows me to change the cathode resistor to run different tubes at different operating points. I don't normally run EL34s in my SSE. When I do I run them as triodes because to me that is where they seem to excel. As pentodes (UL in my case) EL34s don't sound any better than bigger tubes and lack the bass punch of something like a KT88. So when I have bigger tubes in there, they are usually in UL mode. There are a few exceptions to this, however.

Getting back to your question, I get that "warmer" tube sound with more subtle detail at lower volumes with tubes (especially EL34s) strapped as triode. In UL mode, I get more power and more bass with bigger tubes. This is great for playing rock or other beat-heavy music while doing other tasks. My speakers have horn tweeters and they get "shouty" at high volume. This is especially true on a PP amp. A triode SE amp tames them for those times when I am listening to music up close.

BTW, you will get a bit more power than I stated earlier. This numbers are for UL mode. Pure pentode mode would yield a bit more.
  Reply With Quote
Old 31st August 2011, 09:26 AM   #10
Skorpio is offline Skorpio  Denmark
diyAudio Member
 
Join Date: Mar 2004
Location: Denmark
Thank you for you experiences!

I am at the time being satisfied with the troide connection with EL34 and I am using an active subwoofer below 50Hz, so the bass part is not handled by the tubes...

This is a Great little amp! Big thanks to George for his work!!
  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
how to connect an EL34 pentode into a triode and 100ohm resistor between plate and g2 jarthel Tubes / Valves 15 26th October 2013 02:44 PM
EL34 Pentode in Push-Pull! Guijs Tubes / Valves 68 13th February 2013 08:08 PM
Suitable output transformer for SSE? Pilsern Tubelab 5 21st June 2011 04:44 AM
El34 SE pentode alexmoose Tubes / Valves 1 18th July 2006 07:26 PM
EL34 in Pentode Class A? ray_moth Tubes / Valves 7 24th March 2004 05:31 AM


New To Site? Need Help?

All times are GMT. The time now is 02:40 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