Can the 7AK7 computer tube work as audio output tube ? - 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 23rd August 2011, 12:42 AM   #1
aldovan is offline aldovan  Brazil
diyAudio Member
 
Join Date: Jul 2005
Location: Curitiba
Default Can the 7AK7 computer tube work as audio output tube ?

Friends

The forgeten 7AK7 pentode tube can work as audio output tube, with the correct bias ?

Thanks,

Aldovan
  Reply With Quote
Old 23rd August 2011, 03:37 AM   #2
davorin is offline davorin  Croatia
diyAudio Member
 
Join Date: Aug 2005
Location: Zadar, Croatia
I made small Push-Pull guitar amplifier with pair 7AK7 in output: Ua=300V, Ug2=300V(Rg2=470 Ohms for each tube), Ug1=-25V (Set Ia0 to 2x25mA) and Raa=10 KOhms. Output power is >10W, and sound is close to amp with pair of 6V6 tubes.
  Reply With Quote
Old 23rd August 2011, 04:14 AM   #3
diyAudio Member
 
smoking-amp's Avatar
 
Join Date: Dec 2001
Location: Hickory, NC
Putting something like +12 Volts on g3 will square up the curves to be conventional pentode curves. Haven't tried this on the 7AK7, but on 6LE8 and other dual control tubes. Adjust the g3 voltage for minimum g2 current, but don't go too high on the g3 voltage or it will get hot instead.
__________________
I want a Huvr-Board!!
  Reply With Quote
Old 23rd August 2011, 11:35 AM   #4
aldovan is offline aldovan  Brazil
diyAudio Member
 
Join Date: Jul 2005
Location: Curitiba
Default And in triode mode

Quote:
Originally Posted by smoking-amp View Post
Putting something like +12 Volts on g3 will square up the curves to be conventional pentode curves. Haven't tried this on the 7AK7, but on 6LE8 and other dual control tubes. Adjust the g3 voltage for minimum g2 current, but don't go too high on the g3 voltage or it will get hot instead.
And if I use in triode output SE mode ? The connections are the normally used in a pentode ?

Thanks,

ALdovan
  Reply With Quote
Old 23rd August 2011, 12:20 PM   #5
davorin is offline davorin  Croatia
diyAudio Member
 
Join Date: Aug 2005
Location: Zadar, Croatia
Here is first version (with 1 pair of 7AK7), and last version (wit 2 pairs of 7AK7).
I was rewired (for test) all versions in triode mode (G2 to Anode) with better sound, but only 40% of power. Also trayed "realy" triode mode (G2 and G3 to Anode), but did not hear difference.
Attached Images
File Type: jpg 002c.jpg (349.3 KB, 230 views)
File Type: jpg 007b.jpg (184.5 KB, 214 views)
File Type: jpg 002a.jpg (166.0 KB, 206 views)

Last edited by davorin; 23rd August 2011 at 12:32 PM.
  Reply With Quote
Old 23rd August 2011, 12:31 PM   #6
davorin is offline davorin  Croatia
diyAudio Member
 
Join Date: Aug 2005
Location: Zadar, Croatia
Last version is very good gutar amp with ~28W at clipping!
Attached Images
File Type: jpg 007a.jpg (204.0 KB, 205 views)
File Type: jpg 006a.jpg (196.2 KB, 198 views)
  Reply With Quote
Old 23rd August 2011, 01:24 PM   #7
aldovan is offline aldovan  Brazil
diyAudio Member
 
Join Date: Jul 2005
Location: Curitiba
Quote:
Originally Posted by davorin View Post
Last version is very good gutar amp with ~28W at clipping!
Very fine !!!
This tubes are Sylvania ?
You make test with various brands ?

Thanks,

Aldovan
  Reply With Quote
Old 23rd August 2011, 05:50 PM   #8
davorin is offline davorin  Croatia
diyAudio Member
 
Join Date: Aug 2005
Location: Zadar, Croatia
Yes, I was traying with SYLVANIA, RCA, PHILCO and WESTINGHOUSE brands, but all are very closed. PHILCO is mehanically like RCA, and WESTINGHOUSE is like SYLVANIA, and I think there is only 2 manufacturers (RCA and SYLV.). 7AK7 is special "VERY LONG LIFE" tube, with very strong construction and glass, and all good caracterics bether than curent production of tubes. In future, I am planing to made single-end triode conected amplifires for home audio with 3-4 paralel conected tubes (8-10W per chanel).
  Reply With Quote
Old 23rd August 2011, 10:01 PM   #9
aldovan is offline aldovan  Brazil
diyAudio Member
 
Join Date: Jul 2005
Location: Curitiba
Default Tubes

Quote:
Originally Posted by davorin View Post
Yes, I was traying with SYLVANIA, RCA, PHILCO and WESTINGHOUSE brands, but all are very closed. PHILCO is mehanically like RCA, and WESTINGHOUSE is like SYLVANIA, and I think there is only 2 manufacturers (RCA and SYLV.). 7AK7 is special "VERY LONG LIFE" tube, with very strong construction and glass, and all good caracterics bether than curent production of tubes. In future, I am planing to made single-end triode conected amplifires for home audio with 3-4 paralel conected tubes (8-10W per chanel).
I see the Raytheon and Tungsol, too.
The Sylvania "Gold Brand" is a fine option...
I will to buy a SE triode amplifier, because the power do not is problem for me, I use in HIFI with high SPL speakers...
Know this article ? http://www.audioxpress.com/magsdirx/...millet2903.pdf
Pete Millett use a small positive bias in the G3...

Aldovan
  Reply With Quote
Old 24th August 2011, 04:12 PM   #10
diyAudio Member
 
smoking-amp's Avatar
 
Join Date: Dec 2001
Location: Hickory, NC
The positive voltage on g3 is for pentode (or UL) mode to square up the curve set. (g3 winding pitch is too dense in these dual control tubes and so repels a significant portion of the electron stream back to g2 if g3 is at the conventional 0 V. Causing excessive g2 current. Putting some positive voltage on g3 allows most of the electron stream to continue on to the plate for normal pentode operation.) It won't make much difference for triode mode except to shift the g1 bias slightly.
__________________
I want a Huvr-Board!!
  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
6n6p tube as output tube for small guitar amp moonbird Tubes / Valves 28 7th September 2011 04:28 AM
computer tube tester yourownfree Tubes / Valves 34 5th November 2009 03:25 AM
SS or tube voltage amplifying stages in an amp with tube output? ray_moth Tubes / Valves 14 4th July 2007 03:09 AM
Octal tube as headphone amp output tube yagoolar Headphone Systems 6 25th November 2006 09:11 PM
802 as an audio output tube Giaime Tubes / Valves 10 13th April 2006 07:39 AM


New To Site? Need Help?

All times are GMT. The time now is 02:05 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