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 8th June 2008, 03:09 AM   #1
diyAudio Member
 
wrenchone's Avatar
 
Join Date: Feb 2004
Location: Silicon Valley
Default 6CL6 vs. 12BY7A

I have a perverse yen to do an amp project with a pentode first stage, and was thinking of one of these two (it helps that I also have both). I also thought of the 12HG7, but the transconductance is too much for what I have in mind. Any comments regarding linearity, etc., or alternate tubes?.
  Reply With Quote
Old 8th June 2008, 04:21 AM   #2
diyAudio Member
 
Join Date: Nov 2005
Default Re: 6CL6 vs. 12BY7A

Quote:
Originally posted by wrenchone
I have a perverse yen to do an amp project with a pentode first stage, and was thinking of one of these two (it helps that I also have both). I also thought of the 12HG7, but the transconductance is too much for what I have in mind. Any comments regarding linearity, etc., or alternate tubes?.

I believe the 12BY7A has a controlled warm-up filament, and is reputed to be slightly quieter than the 6CL6. The 6CL6 however seems more readily available, and most tests show that these tubes are nearly equivalent in use, running at similar operating points. Both are capable of swinging gigantic voltage at low distortion. User Boris_the_Blade has done some extensive 6CL6 differential amp tests, and uses them as a driver for a PPP EL34 amp. You can also find some pentode comparisons on Pete Millett's site (Pentodes).

Personally, I'd use whichever I had more of at the time
  Reply With Quote
Old 9th June 2008, 04:15 PM   #3
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
I had a Citation II which used 12BY7A pentodes in the input and driver stages, not sure that the 6CL6 differs significantly, but I had a lot of problems with microphonic 12BY7A particularly in the first stage. Either way you should probably plan on getting few extras so you can select the least microphonic ones for use.
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 9th June 2008, 11:54 PM   #4
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
The "best" 12BY7s in a "Duece" are RCA in the voltage gain positions and GE JAN in the splitter positions. Set up a "12" V. heater supply and RCA 7054s enter the picture.

Remember, the Cit. 2 has well over 30 dB. of NFB in 3 nested loops. The outer, global, loop applies only a few dB. Stu Hegeman leveraged bandwidth throughout the design to make the "gobs" of NFB work well.
__________________
Eli D.
  Reply With Quote
Old 10th June 2008, 01:18 AM   #5
diyAudio Member
 
Join Date: Nov 2005
Quote:
Originally posted by Eli Duttman
The "best" 12BY7s in a "Duece" are RCA in the voltage gain positions and GE JAN in the splitter positions. Set up a "12" V. heater supply and RCA 7054s enter the picture.
Have you determined this by measurement, or by listening? The reason I ask is, after much experimentation, I agree 100% on a "sonic" basis. Another good trick is a 12BV7 for the first stage, which has slightly higher transconductance and gives you a touch of extra global-NFB -- I use some early ones with the smoked glass that look sweet in that position.
  Reply With Quote
Old 10th June 2008, 01:49 AM   #6
diyAudio Member
 
Miles Prower's Avatar
 
Join Date: May 2005
Location: USA
Blog Entries: 6
Default Re: 6CL6 vs. 12BY7A

Quote:
Originally posted by wrenchone
Any comments regarding linearity, etc., or alternate tubes?.
You can check it out at Frank's: 12BY7A. A good loadline for the 12BY7A is going to require a rather stiff plate current, and lotsavolts. Of course, this being designed as a vid amp for colour TVs, it needed enough current sourcing to avoid slewing at a 4.0MHz top end, and high voltage is easy to come by in a colour TV set. I've got a few of 'em, but so far, I haven't needed that much gain. It could be one of those types that're gonna be hard to come by since lots of ham rigs used these as RF drivers.
__________________
There are no foxes in atheistholes
www.dolphin-hsl.com
  Reply With Quote
Old 10th June 2008, 02:10 AM   #7
diyAudio Member
 
HollowState's Avatar
 
Join Date: Aug 2006
Location: Taxland, New Jersey
Quote:
Originally posted by Eli Duttman
The "best" 12BY7s in a "Duece" are RCA in the voltage gain positions and GE JAN in the splitter positions. .
I tend to agree with Eli since I've used them all. (well almost all) These are the best I've ever found. They're curve tracer matched and selected by Tek. If you ever find any, they're well worth the price for the diff. pair.

Victor
Attached Images
File Type: jpg tek 12by7s.jpg (75.2 KB, 386 views)
__________________
"It is hard to imagine a more stupid or more dangerous way of making decisions than by putting those decisions in the hands of people who pay no price for being wrong." ~Thomas Sowell
  Reply With Quote
Old 10th June 2008, 02:20 AM   #8
diyAudio Member
 
Join Date: Nov 2005
Quote:
Originally posted by HollowState

These are the best I've ever found. They're curve tracer matched and selected by Tek. If you ever find any, they're well worth the price for the diff. pair.

That's exactly what I run. You can get matched 6CL6s in the same form, too. Nice stuff!
  Reply With Quote
Old 12th June 2008, 05:38 AM   #9
diyAudio Member
 
wrenchone's Avatar
 
Join Date: Feb 2004
Location: Silicon Valley
What I'm probably going to use first off after some thought is a 6AH6 in full pentode mode driving a source follower, which in turn will drive an enhanced triode (screen drive) mode sweep tube. The 6AH6 has almost as much transconductance as the 6CL6 and 12BY7 and doesn't require as much plate current to get the benefit of its goodness. Cheap and plentiful, too. Comments?
  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
6AU6, 6U8, 6CL6, plus UTC A-10 make Mic Pre? tablebeast Tubes / Valves 4 5th October 2005 06:20 AM
found two boxes of GE 6CL6 tubes moonshow Tubes / Valves 19 24th September 2005 12:14 AM
I'm Looking for some 12BY7A Tubes alaskanaudio Swap Meet 3 19th March 2002 09:21 PM


New To Site? Need Help?

All times are GMT. The time now is 09:22 PM.


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