Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Aikido Cathode Follower Input Impedance
Aikido Cathode Follower Input Impedance
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 10th November 2017, 09:39 AM   #11
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
R7 appears to be merely a ground leak for the output coupling cap. Replacing it with a choke would give quicker stabilisation of output DC voltage, and would narrow the bandwidth and increase distortion - although not by much. Hard to see how this might be a good idea.
  Reply With Quote
Old 10th November 2017, 11:05 AM   #12
moley is offline moley
diyAudio Member
 
Join Date: Sep 2010
Quote:
Originally Posted by Steve Morley View Post
In my experience with the Aikido circuits: 6CG7 = warm and tubey, 6DJ8 = much more incisive (depending on tube chosen). Russian reissue E88CC Genalex is a decent sounding tube. Avoid the ECG Philips (and others of similar USA manufacture). The sound is dreadful.
6DJ8 will have a lower output impedance than a 6CG7, see Zo on the chart. Also you can run 6DJ at 150 to 200 volts where the 6CG usually runs 250 to 350, if that makes any different to you.

Steve With no annoying tag line. Oops.

Thanks for this, I was actually thinking of asking for recommendations for tubes, but there are so many old Aikido threads asking similar questions that I thought folk might by tired of replying to such questions.

I was looking at the table and 6DJ8 looks the best candidate from an output impedance point of view. Your description of 6DJ8 vs 6CG7 also suggests this would suit my system and taste better.

Any other recommendations for 6DJ8 or equivalent tubes would certainly be very welcome.

Quote:
Originally Posted by kodabmx View Post
If you build it point to point like I do or you get an adaptor a 5670/6N3P is great with a 220R R3/R6 250V.

I had thought about point to point and would like to do this ideally, but would not feel confident so I have gone with the full kits including PCBs. Actually, reading as much as I can on these forums about the Aikido kits is making me feel a little nervous about the build!

I have successfully put together a good number of kit based projects previously, but they have generally been more straight forward in that there were fewer or no options and "forks in the road" as such. I also keep coming across mentions of bags being labelled incorrectly or mistakes in the instructions / schematics with the glassware kits.
  Reply With Quote
Old 10th November 2017, 01:18 PM   #13
Steve Morley is offline Steve Morley  Canada
diyAudio Member
 
Join Date: Jan 2015
Location: Georgian Bay
Default One minor flaw with some of the Aikidos....

Is that sometimes tube designators will be reversed. For instance V1, the input tube for one channel will be labelled V2, the input tube for the other, and vise versa. It can drive you a bit nuts if you are trying to compare the board to the schematic.


The instructions are fairly basic, you don't get the "Heathkit" style of detail.


I've not had any parts mislabelled but you might get several values for some of the resistors. You choose depending on the tube you use or in the case of a power supply the output voltages you want.


See the following for details on an Aikido build and 6DJ8 tube shootout.


Cheers, Steve (first snow of the season here last night )


Battle of the Cheap Line Stages – Part 1 | Wall of Sound | Audio and Music Reviews


Vacuum Tube Shootout: 6DJ8 types (part 1) | Wall of Sound | Audio and Music Reviews


Vacuum Tube Shootout: 6DJ8 types (part 2) | Wall of Sound | Audio and Music Reviews
  Reply With Quote
Old 10th November 2017, 01:22 PM   #14
moley is offline moley
diyAudio Member
 
Join Date: Sep 2010
Thanks a lot for your help that's great. I shall have a good read of those threads.

The PS1 kit and the ACF kit have just been delivered an hour ago! I chose to get all of the resistors with the ACF so i should be covered for a few options. Just got to do some reading / planning I guess now.
  Reply With Quote
Old 10th November 2017, 01:40 PM   #15
kodabmx is offline kodabmx  Canada
diyAudio Member
 
Join Date: Oct 2011
Location: Toronto
There's also a thread on here about the ACF and how a lot of people can't get rid of a low level hum with the kit. Let us know how you fare.
  Reply With Quote
Old 10th November 2017, 02:35 PM   #16
moley is offline moley
diyAudio Member
 
Join Date: Sep 2010
Quote:
Originally Posted by kodabmx View Post
There's also a thread on here about the ACF and how a lot of people can't get rid of a low level hum with the kit. Let us know how you fare.
Is that the version 2 of the ACF? I did see that on this and another forum.
I think the ACF2 with integrated bi polar PSU is different to the standard ACF.
  Reply With Quote
Old 10th November 2017, 02:38 PM   #17
moley is offline moley
diyAudio Member
 
Join Date: Sep 2010
If we are talking about the same kit and same problem, this is what i found regarding that issue which I think is specific to the ACF2 if I have understood correctly.

I was actually considering the ACF2 until i read this and a number of other posts about hum issues.

Removing hum from Aikido Cathode Follower (ACF-2 9-Pin) - diyAudio
  Reply With Quote
Old 10th November 2017, 07:29 PM   #18
kodabmx is offline kodabmx  Canada
diyAudio Member
 
Join Date: Oct 2011
Location: Toronto
When I built the circuit I omitted the Aikido mojo. It's simply a cathode follower with an active load now.
Attached Images
File Type: png ACF-buffer-6N8S.png (27.7 KB, 140 views)
  Reply With Quote
Old 15th November 2017, 06:16 PM   #19
moley is offline moley
diyAudio Member
 
Join Date: Sep 2010
one thing I haven't quite got my head around when looking at the impedance of connected bits of kit is the output impedance. Are these also in parallel with each other in the same way that input impedance is?

In my example looking at the 333K input impedance of the Aikido ACF, this is in parallel with the input impedance of the POT that I chose, so if I use a 50K standard POT the source component sees 43472.58 ohms.

Is the output impedance of both the 50K POT (12.5K half volume highest point) and source (3.5K) in parallel? i.e. 2734.38 ohms?
  Reply With Quote
Old 16th November 2017, 12:15 AM   #20
jameshillj is offline jameshillj  Australia
diyAudio Member
 
Join Date: Feb 2005
Location: Melbourne
Koda,
Did the simplified circuit meet your expectations of the sound?

Thanks Steve for the links to the reviews - very clear and surprisingly 'insightful' (if that's a word).
  Reply With Quote

Reply


Aikido Cathode Follower Input ImpedanceHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Aikido Cathode Follower HUM Problem volvoturbo Tubes / Valves 4 30th March 2015 09:29 PM
Input impedance on cathode follower stage? Vingborg Tubes / Valves 19 11th February 2015 10:38 AM
Aikido Cathode Follower preamplifier with remote ClefChef Tubes / Valves 5 17th June 2014 12:35 AM
Aikido Cathode Follower Bengali Tubes / Valves 18 28th August 2013 09:41 PM
Cathode Follower Buffer Input Impedance xcortes Tubes / Valves 5 1st December 2005 05:10 PM


New To Site? Need Help?

All times are GMT. The time now is 11:29 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki