12B4 vs. 12B4A - 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
Reply
 
Thread Tools Search this Thread
Old 20th March 2013, 12:54 AM   #1
diyAudio Member
 
Richard Ellis's Avatar
 
Join Date: Sep 2006
Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.
Default 12B4 vs. 12B4A

I may have a problem here, I have a quad of 12B4/As and I think pairing a 12B4 with a 12B4A will REALLY screw things up.
As I understand it the "A" version is a "slow start" version, the 'standard 12B4 is not. Paralleled on the outputs one will come up to temperature well before the other, drawing more current initially before the other....Bad idea? Smokin' bad idea?


__________________________________________________ _____Rick.........
Attached Images
File Type: gif 12B4Amp.gif (6.8 KB, 161 views)
  Reply With Quote
Old 20th March 2013, 01:04 AM   #2
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
if you have them connected like that , do not worry
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
  Reply With Quote
Old 20th March 2013, 01:52 AM   #3
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
In 7 and 9 pin mini tubes, the "A" type suffix indicates controlled heater warmup time. That is of consequence ONLY when series heater strings are employed.

BTW, do you have heater current to spare? If so, get the nasty, non-linear, 12AU7 out and a linear 12BH7 in.
__________________
Eli D.
  Reply With Quote
Old 20th March 2013, 02:39 AM   #4
diyAudio Member
 
Richard Ellis's Avatar
 
Join Date: Sep 2006
Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.
Eli.........I have a 3A heater, the four 12B4s' will take 2.4A of that....I have a 'spare' TX split-bobbin at 12VRMS that I want to run thru a 317 to run the 12XXX. I have a AX and an AT .....I'll assume the AX runs "too hot"....I don't know about the AT...............don't have a BH. If I can readily get a BH........Is it a drop-in or do I have to re-bias??

__________________________________________________ ________Rick.......
  Reply With Quote
Old 20th March 2013, 02:45 AM   #5
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
A 12BH7 will go in a 12AU7 "hole" without any wiring changes, IF sufficient extra heater current is available. The 12BH7 draws twice the heater current.
__________________
Eli D.
  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
12B4 Battery Bias from (Preamp: Foreplay or 5687 or 12B4 ) DougL Tubes / Valves 3 2nd August 2004 06:06 PM


New To Site? Need Help?

All times are GMT. The time now is 10:56 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