Help with a cathode coupled pentode driver? - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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
Thread Tools Search this Thread
Old 26th July 2006, 08:41 AM   #1
diyAudio Member
Join Date: Oct 2003
Location: Christchurch
Default Help with a cathode coupled pentode driver?

Will this work?
Will I see ~-90 V at the grid of the 211?

How will I bias the 5881? By varing the G#2 voltage?
Attached Images
File Type: jpg driver1.jpg (23.1 KB, 135 views)
  Reply With Quote
Old 26th July 2006, 12:50 PM   #2
SY is offline SY  United States
diyAudio Moderator
SY's Avatar
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
What's the point of the plate choke? How do you intend to decouple the screen to the cathode? There are a lot of ways of getting the bias right- a CCS in the cathode instead of the choke might be the easiest. And a CCS will cost about 5% of a good choke.
"Pity, wrath, heroism, filled them, but the power of putting two and two together was annihilated."- EM Forster
  Reply With Quote
Old 26th July 2006, 02:06 PM   #3
diyAudio Member's Avatar
Join Date: Jul 2005
Location: West Virginia panhandle
Will I see ~-90 V at the grid of the 211?
No you won't. The DC resistance of your cathode choke is low. You will see -230 volts + the IR drop across the choke which depends on the tube current and the DC resistance of the choke. With the tube bias fixed at -90 volts the tube current will be very high, and something will have a short unhappy life. Either the 5881 or the choke.

Substitute a CCS or a resistor for the cathode choke. You need the ability to drop about 130 volts. The plate choke is not needed (but might not hurt anything). The screen should be decoupled to the cathode as SY suggested. You need a capacitor from the screen to the cathode.
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote


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
TX coupled, pentode linestage Bandersnatch Tubes / Valves 14 21st May 2010 05:26 PM
Direct-coupled cathode/source follower driver in PP? ray_moth Tubes / Valves 83 17th July 2008 03:53 AM
Cross-coupled NFB for PP Pentode ray_moth Tubes / Valves 3 24th January 2006 12:18 PM

New To Site? Need Help?

All times are GMT. The time now is 05:53 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright 1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2