12v B+ Tube buffer 12AX7 - Page 2 - 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 19th September 2010, 09:23 PM   #11
diyAudio Member
 
Globulator's Avatar
 
Join Date: Aug 2004
Location: Cambridge, England.
Quote:
Originally Posted by benproiii View Post
can i use the 12at7

The gain from max to min goes 12AX7 -> 12AT7 -> 12AU7

In general you can plug and play between these three tubes without issue, just listen and see which you prefer. The load lines vary of course but they will all still work
  Reply With Quote
Old 19th September 2010, 09:42 PM   #12
diyAudio Member
 
Join Date: Aug 2010
i modified the circuit i just want to know before i build it how much gain it will have and what the input and output impedances will be.
Attached Images
File Type: jpg 12at7.jpg (126.2 KB, 255 views)
  Reply With Quote
Old 19th September 2010, 10:31 PM   #13
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Output impedance will be 5-6k (that's high), input impedance will depend on volume control setting, distortion will be in double figures (ditto). You didn't ask, but it will also hum like crazy.
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 19th September 2010, 10:50 PM   #14
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
There seems to be a rash at present of people wanting to add distortion to their sound by running valves from 12V supplies. Does this always happen at this time of year?

If you want to add some "tubey sound" to a line source you can do it with a couple of resistors and a silicon diode, no need for a power supply. Put a resistor in series with the signal, say 4K7. Then from the output put a 10K plus a diode in series to ground. This will gently clip signals above about 600mV, and add some distortion to slightly smaller signals. Low level signals will be unaffected. Roughly the same response as a badly biassed valve, but much cheaper.
  Reply With Quote
Old 20th September 2010, 12:23 AM   #15
piano3 is offline piano3  United Kingdom
diyAudio Member
 
Join Date: Aug 2010
Location: London,UK
Superb!
  Reply With Quote
Old 20th September 2010, 12:43 AM   #16
diyAudio Member
 
Join Date: Aug 2010
can somebody give me a circuit for a buffer that uses the 12ax7, 7025, 12at7 tube. it adds 2 to 4x gain and is not too distorted. (normal b+ voltage) and it can have a computer as sound input and a tda7294 as the output.
  Reply With Quote
Old 20th September 2010, 02:48 AM   #17
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
For a 2-4x gain and low source impedance, those just aren't good choices of tubes. It's like saying, "I need to haul large numbers of people, what's the best among Mini-Cooper, Miata, and Smart?" You want to look at low mu, low plate resistance tubes like 12B4.
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 20th September 2010, 12:09 PM   #18
diyAudio Member
 
Join Date: Nov 2007
Location: Dallas
Click the image to open in full size.

Lots going on here, for full explanation and LTSpice sim files:
Tube can work in low volt~~fix your knowledge
  Reply With Quote
Old 20th September 2010, 01:42 PM   #19
soro is offline soro  Taiwan
diyAudio Member
 
Join Date: Jul 2010
Location: Taipei
Send a message via MSN to soro
12V B+ tube+Opamp. It can use 12AU7 12AX7 6DJ8 6922...
Attached Images
File Type: jpg headphone-amp.jpg (33.8 KB, 183 views)
File Type: jpg DSCN4230-1.JPG (120.4 KB, 180 views)
File Type: jpg DSCN4265-1.JPG (123.6 KB, 162 views)
  Reply With Quote
Old 20th September 2010, 01:49 PM   #20
diyAudio Member
 
Join Date: Nov 2007
Location: Dallas
R2 shoulda been split and bootstrapped off the output of that op-amp.
Plate voltage already so low, grid leak will either pull the bias negative,
and/or rectify like a diode... plate current will get stOOpid small.

6DJ8 and 6922 heaters are hard wired in series for 6V3. The middle tap
given up to a shield between the triodes. No 12V6 option except drop
the excess voltage somewhere else...

Oh, nevermind... I see now the LM317 0A3 current supply.

Last edited by kenpeter; 20th September 2010 at 02:18 PM.
  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
12AX7 Tube Question duanestorey Tubes / Valves 7 12th April 2010 04:34 AM
Tube Buffer? 12ax7? wttaylor Tubes / Valves 10 24th February 2010 02:40 AM
How to get a buffer with overdrive from a 12AX7 ? -_nando-_ Tubes / Valves 7 27th July 2006 02:00 AM
12V trigger buffer MtBiker Solid State 1 18th July 2005 11:00 PM
12v for 3875 and 35v for tube buffer? jsaults Chip Amps 3 7th March 2005 11:34 AM


New To Site? Need Help?

All times are GMT. The time now is 03:40 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