12B4A Linestage & PSU - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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 August 2003, 11:50 PM   #1
G is offline G  United States
diyAudio Member
G's Avatar
Join Date: Apr 2002
Location: Belleville, IL.
Default 12B4A Linestage & PSU

Here is my modest attempt at designing a linestage with the 12B4A tube. I think it will give good performance. The Rp is so low that there shouldn't be too much distortion at the output. The gain of this circuit is low ( 4? 5? ) but I don't need much if any. I decided on a anode follower because evidently CF don't have very good PSRR. So I think I will give this a shot a see how it sounds. I'll let you know.

Attached Images
File Type: gif 12b4a linestage & psu(small).gif (18.3 KB, 1765 views)
  Reply With Quote
Old 27th August 2003, 01:02 AM   #2
diyAudio Member
Join Date: Jul 2003
Location: Ann Arbor, MI
I will have to say that the 12B4 is a good linestage tube. I personally like the 12SN7 better, but that is not important at this time. In the experimenting I did with the 12B4, I found that 180-200 volts on the plate sounded best at 10 mA of current. LED biased to near 30 volts at the cathode( 14 red ones, one yellow). I never tried this one with a resistive load, and went straight to cascoded mosfets.
I also use the 12B4 as a driver stage in the PP amps, choke loaded and common cathode, diff-pair rigging( CT choke ). The tube exhibits less increase in plate resistance as voltage increases than most( actually, any that are comparable in performance )., and can stand 5-600 volts on its plate without worry. And the open anode structure lets those big cathodes glow for all to see. Toooo cool!!!
the Tnuctipun will return
  Reply With Quote
Old 27th August 2003, 02:20 AM   #3
diyAudio Member
Brett's Avatar
Join Date: Jan 2002
Not too bad at all. But contrary to Douglas' opinion, I fond the 12B4A in a linestage runs better with about 100Va-k and about 25 - 35mA. So my suggestion would be to adjust the bias resistor down to about 440R (vg = -11V) and adjust the dropper in the PSU to get it to 310V again. Gain will be around 5 and the output Z ~ 900R

Better still would be to ditch the last RC in the PS and up the value of the anode R to about 10k keeping the current around 25mA. You'll need a 25W resistor for that; 2 x 5k 12W Mills in series or 2 x 20k in // would be fine.
  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
12B4A Linestage Bryan Tubes / Valves 223 16th December 2010 08:57 PM
12B4A + LL1671 Linestage Fuling Tubes / Valves 5 14th November 2007 02:30 PM
yet another 12b4a zobsky Tubes / Valves 11 24th May 2004 11:56 PM
12b4a Jack Thomas Tubes / Valves 50 7th September 2002 03:29 PM

New To Site? Need Help?

All times are GMT. The time now is 07:24 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2