Octal Aikido? What tubes? - 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 29th December 2006, 09:44 PM   #1
jayme is offline jayme  United States
diyAudio Member
 
Join Date: Sep 2005
Default Octal Aikido? What tubes?

I've got an all 6SN7 aikido linestage, and it just sounds so good that I've been unwilling to mess with it.

However, I have a couple alternative tubes sitting here: 6BX7s and 6080s.

Anyone try any non-6SN7s in an octal aikido?


My power transformer has enough heater current for any combo of these tubes, and I can easily adjust my B+ from 324V downwards to about a 200V minimum using a resistor/cap PS stage.

I've currently got the 6SN7s running at 324V B+, with 1000R resistors biasing the input tubes to ~4mA and 330R resistors biasing the output tubes to ~11mA. (Pretty much exactly what Broskie recommends for the 6SN7s...)

If I were to drop the 6BX7 or 6080 into the input stage, I'd lower the input tube bias resistor to 500R, and adjust the B+. In the output stage, I'd pretty much leave the biasing resistors as-is, change the B+, and change the PS-noise injection resistor.
  Reply With Quote
Old 29th December 2006, 10:05 PM   #2
Sheldon is offline Sheldon  United States
diyAudio Member
 
Join Date: Dec 2003
Location: San Diego
I trust you are using this table:

http://www.tubecad.com/2006/05/blog0064.htm
  Reply With Quote
Old 30th December 2006, 12:47 AM   #3
jayme is offline jayme  United States
diyAudio Member
 
Join Date: Sep 2005
I am indeed using that table.
  Reply With Quote
Old 30th December 2006, 01:54 AM   #4
diyAudio Member
 
aletheian's Avatar
 
Join Date: Apr 2004
Location: Philly
I built a 6SJ7/6922 Aikido. Sounded great!
__________________
Heghlu'meH QaQ jajvam!
  Reply With Quote
Old 30th December 2006, 09:30 AM   #5
Giaime is offline Giaime  Italy
diyAudio Member
 
Giaime's Avatar
 
Join Date: Oct 2004
Send a message via MSN to Giaime
Hello Jayme,

you have a beautiful name

I heard the Aikido with 6SN7 frontend and 6AS7 output. It was at a friend of mine's house, he had to drive about 5m unbalanced cables up to his power amps, near the speakers. So he needed lowish output impedance. It did sound quite good, but I wouldn't suggest it if you haven't those particular needs.

But as far as I understand, the most important tube choice for Aikido is the first tube, the output tube does make a difference but not greater than swapping around a couple of brands of 6SN7 (I like russian ones...).

Just my 0.02
  Reply With Quote
Old 30th December 2006, 03:15 PM   #6
Sheldon is offline Sheldon  United States
diyAudio Member
 
Join Date: Dec 2003
Location: San Diego
Quote:
Originally posted by Giaime
But as far as I understand, the most important tube choice for Aikido is the first tube, the output tube does make a difference but not greater than swapping around a couple of brands of 6SN7 (I like russian ones...).
Just my 0.02
I would think (without any direct experience myself), from a design standpoint that this would logically be so. The first tube sets the gain and does the voltage amplification so it will largely determine the character and distortion profile of the amplifier.

The second tube functions as a buffer, and as long as it can provide sufficient current at low distortion, change to a different tube that also meets the requirements should have less effect on the sound. Of course, if you are driving a low impedance loads, long cables, etc., then switching from a higher impedance tube to a lower impedance set-up in the second position could well make an audible difference.

Sheldon
  Reply With Quote
Old 30th December 2006, 09:35 PM   #7
jayme is offline jayme  United States
diyAudio Member
 
Join Date: Sep 2005
Quote:
Originally posted by aletheian
I built a 6SJ7/6922 Aikido. Sounded great!
Interesting. I assume you would need 2 6SJ7s per channel for the inputs. The only drawback I see to the separate bottles is that heater noise is not exactly the same, so is not cancelled as it would be in a single-bottle dual triode in the Aikido setup.

Also, was the 6SJ7 triode-strapped? And by "Sounded great!" I infer that you don't have it anymore...did you give it away or disassemble it?
  Reply With Quote
Old 30th December 2006, 11:13 PM   #8
diyAudio Member
 
Join Date: Nov 2002
A 6AU6/5687 also makes a very nice line stage. Only one 6au6 is used per channel.

My bad! I guess I should have read the "octal" in the subject.
  Reply With Quote
Old 31st December 2006, 03:03 AM   #9
diyAudio Member
 
aletheian's Avatar
 
Join Date: Apr 2004
Location: Philly
Quote:
Originally posted by jayme


Interesting. I assume you would need 2 6SJ7s per channel for the inputs. The only drawback I see to the separate bottles is that heater noise is not exactly the same, so is not cancelled as it would be in a single-bottle dual triode in the Aikido setup.

Also, was the 6SJ7 triode-strapped? And by "Sounded great!" I infer that you don't have it anymore...did you give it away or disassemble it?

i just wanted to try an octal input pentode. I tried it in both pentode and triode strapped... after some tweaking, it was pretty dead quiet in either mode, but it took a little trial and error.

And Yes, I only breadboarded it... i didn't leave it together, and the tubes are now back in my collection.
__________________
Heghlu'meH QaQ jajvam!
  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
FS Aikido Octal linestage $75 nvrgdenuf Swap Meet 2 29th December 2008 08:35 PM
Calculating PS current for octal Aikido jrebman Tubes / Valves 4 25th March 2008 08:47 PM
Aikido Tubes 2KW Tubes / Valves 47 13th July 2007 12:16 AM
Low gain 9-pin tubes for Aikido? gurevise Tubes / Valves 8 2nd January 2007 11:51 PM
Octal tubes for 7695-style matrix amp? bst Tubes / Valves 3 15th November 2006 08:52 AM


New To Site? Need Help?

All times are GMT. The time now is 03:58 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