Aikido line stage results? share yours - 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 11th September 2005, 02:01 PM   #1
diyAudio Member
 
Craig405's Avatar
 
Join Date: Jul 2005
Location: Sussex
Default Aikido line stage results? share yours

Hi,

I have just finished and tested 2 aikido amplifiers using 12AX7's in gain stage and 12AT7's in buffer.
PSU is 375V 150mA transformer, 5Z4 rectified with plenty of capacitance and a 20H choke.
Each channel is seperatly tube regulated using 2x0D3 and 2x0C3 giving 265V per amp.

Tubes used in the Aikido are 12AX7's for gain and 12AT7's for buffer.
I get about 2mV PSU junk/HF junk on output of each channel which is ok i guess.

My frequency response is from almost DC to 50Khz (-3dB).
Gain is around 15 but my tubes are dodgy and old so it might be completely different.

Will a transistor CCS before the regulators help the 2mV noise?

What specs is this amp supposed to have and what specs have people got from building it?

How much thump do you get turning it on, i get about 5V on and 3V off (enough to mash my speakers ,when i eventually hook it up ) is this normal?

Output offset is about 30mV.

I would be interested to know what success people have had with this amp as i have heard it is very popular.

long post hehe

Cheers
Craig
  Reply With Quote
Old 11th September 2005, 02:57 PM   #2
diyAudio Member
 
Join Date: Feb 2002
Craig - I'm no help w/measurements for my unit (which is 6SN7/6SN7), but in any case I'd expect that there may be something up with yours: gain should be more like 50 than 15.

Subjectively I'm very happy with mine, no plans to change it anytime soon at all.

Re: turn-on, did you use the "safety" voltage dividers Broskie added in a later blog? They should help with turn-on (although those voltage regs do turn-on quite suddenly, that might be the issue.)

Best,

-j
  Reply With Quote
Old 11th September 2005, 06:16 PM   #3
diyAudio Member
 
Craig405's Avatar
 
Join Date: Jul 2005
Location: Sussex
J Epstein, yea i used the dividers.
I might recheck the gain, that is a massive difference, although i dont know the gain of the tubes you used.
I havnt actually listened to mine yet (lackng my power amp for a bit) but i hope its as good as some people have said.
i might create a mute using Jfet's to short the o/p ofter the capacitor for a few seconds at turn on and maybe at turnoff too.

Craig
  Reply With Quote
Old 11th September 2005, 08:48 PM   #4
diyAudio Member
 
Join Date: Mar 2005
Location: mid wales
mine is quiet turning on and off
no noise i can hear at output either
but i'm just using two 20H chokes
choke input with two 470uf caps
and a 1k>470uf RC stage to drop the voltage

i have run mine with 12ax7 > 12at7
that had way too much gain
but sounded ok
though not as good as with 12au7 CF

i'm now using 6n1p > 6n6p and it is wonderful

dave dove
  Reply With Quote
Old 12th September 2005, 12:42 AM   #5
dmcgown is offline dmcgown  United States
diyAudio Member
 
Join Date: Jul 2002
Location: Silver Spring, Maryland, USA
Just a few comments regarding Aikido power supply...

First, I recommend using a CCS in place of a resistor feeding the shunt regulators, it will help reduce noise and grunge even though the Aikido supply is fairly good in doing this intrensically.

Regarding a turnon thump, I would strongly recommend installing a mute switch or time delay relay that will ground the outputs until the regulators light off. That being said, the sound is really just annoying, it doesn't do any damage, at least in my system.

Also, I have found that power supply capacitor quality and size is clearly audible, even with shunt regulation with CCSs (I am using a similar arrangement with series 0A2s for a 300V B+). I would recommend using as small value as you can get away with without comprimising the hum or hash on the outputs). If using electrolytic caps, bypass them with signal quality film or oil caps.

That being said, the Aikido circuit is capable of very low level resolution, the naturally low PSRR means that meticulous attention to PS quality will reap great benefits in resolution.

Just one comment to Dave Dove, regarding the problem I was having a few weeks ago concerning excessive noise that I thought was attributed to the safety resistor divider, I subsequently found that the 12FQ7s I was using at the time had a problem with poor heater insulation that was producing excessive buzz noticable through my 105dB efficient horn speakers. Using a different tube solved the problem. Thanks for all the thought and effort in your comments to me on the problem.

David
  Reply With Quote
Old 12th September 2005, 10:20 AM   #6
diyAudio Member
 
Craig405's Avatar
 
Join Date: Jul 2005
Location: Sussex
Dave, nice thanks for the reply 6N1P are pin compatible i take it? I might give them a try, what cathode resistors do you use with them and HT voltage.

dmcgown,
I will certainly add a CCS then, definatly solid state because i dont have much room left inside my case after all those regulators .
My PSUcaps (~80uf per channel) consist of 3 smaller caps in // with a 340nf cap accross their output.

I think Jfets are a good solution to the thump, more compact and reliable than relays but to get the output muted on turnoff might be tricky.

Thanks for your posts.

Craig
  Reply With Quote
Old 12th September 2005, 01:41 PM   #7
heater is offline heater  Finland
diyAudio Member
 
Join Date: Jul 2004
Location: Helsinki
dmcgown:

"That being said, the Aikido circuit is capable of very low level resolution, the naturally low PSRR means that meticulous attention to PS quality will reap great benefits in resolution."

I don't understand your comment. I thought the whole point of the Aikido concept was to have a very good PSRR.
__________________
For me the past is not over yet.
  Reply With Quote
Old 12th September 2005, 01:47 PM   #8
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Blog Entries: 18
Quote:
I don't understand your comment. I thought the whole point of the Aikido concept was to have a very good PSRR.
True..I guess that is what he meant.
  Reply With Quote
Old 12th September 2005, 03:38 PM   #9
diyAudio Member
 
Join Date: Mar 2005
Location: mid wales
craig45

6n1p and 6n6p are not pin compatible with 12at7 etc
they have 6.3v heaters on pins 4 and 5 with pin 9 to ground

simple enough if you have 6.3v source

i am using JB's original circuit for 6n1p and 5687
220vHT 430Rk
i feel no need to mess

dmcgown

you're welcome

dave dove
  Reply With Quote
Old 12th September 2005, 10:39 PM   #10
diyAudio Member
 
Join Date: Jul 2003
Location: Auckland
I have been working on a SN7 Aikido breadboard.
Very, very good sound.Open and airy sound. Very transperent.
I used another of Broskie's ideas as well, works great. 18.9 volt heater transformer with 21 ohm resistors on each valve. I can plug in any 6,8 or 12 volt SN7 or such. Then I used 19AX7 damper diodes off the same transformer. These diodes are cheep as chips and sound good.
I found the power supply quite critical. The sound of caps quite noticeable. I now have ..10H , 10uf Solen, 10H, 20uf Solen, 500ohms 30uf Solen, 10H, 50uf motor run, 10H 100uf motor run.Sounded better than NOS oils or Cerafines and or a less complex supply.
Mucking around with volume pots was interesting. Vishay 1M cermet law faked with carbon comp 50k is very transperant. Will try it as a series conection next.
Cheers.
  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
Aikido All in One line stage amp PCB Evenharmonics Tubes / Valves 13 24th October 2009 03:33 PM
Aikido line stage - plus phono line stage cjkpkg Tubes / Valves 1 22nd November 2008 09:50 PM
Aikido Line Stage Bengali Tubes / Valves 6 10th September 2007 10:51 AM
Improving the Aikido line stage... Bas Horneman Tubes / Valves 144 10th February 2006 04:00 AM


New To Site? Need Help?

All times are GMT. The time now is 06:27 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