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Aikido Cathode Follower

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D

DualTriode

Member
Joined 2009
Bengali said:
Hi,

has anyone built JB's aikido cathode follower?
how do you like the sound?
I like that is only uses 2 tubes but no gain.

Which would you prefer? 4 tubes with gain or 2 tubes without for a pre?

Which 6cg7 NOS tubes brands are good buy on ebay?
Click to expand...

Hello,
I have built 3 ACF’s. Two point to point and one on the new PCB. I am pleased with the performance of the ACF.
What I like about it is this, the sound is solid, it has a boot in the face slam that was missing with the CD player connected to the power amplifier. The ACF is very clean and very quiet. Why not an Aikido you say? A gain of one is just what is needed any higher gain is burned up in the attenuator. I use it between the output of the RIAA preamplifier and a SET power amplifier. The BCF drives the interconnects and power amplifier easily. I use a ACF to drive a pair of Triode Power Tubes (no other driver) for my headphone amplifier. Again very clean and quiet.
RCA NOS
DT
All just for Fun!
 
Last edited:
B

Bengali

Member
Joined 2006
Hello,
I have built 3 ACF’s. Two point to point and one on the new PCB. I am pleased with the performance of the ACF.
What I like about it is this, the sound is solid, it has a boot in the face slam that was missing with the CD player connected to the power amplifier. The ACF is very clean and very quiet. Why not an Aikido you say? A gain of one is just what is needed any higher gain is burned up in the attenuator. I use it between the output of the RIAA preamplifier and a SET power amplifier. The BCF drives the interconnects and power amplifier easily. I use a ACF to drive a pair of Triode Power Tubes (no other driver) for my headphone amplifier. Again very clean and quiet.
RCA NOS
DT
All just for Fun!
Click to expand...

Thanks DT.

I appreciate the great feedback. I will try one.

What's your preference for power supply with the BCF?

Which tubes did you decide on?

I will keep an eye out for the RCA NOS tubes.
 
S

Sheldon

Member
Joined 2003
6dj8 or equivalents are a good choice. The heaters are designed for cascode operation, so the heater to cathode voltage is not a problem. And they work well at relatively low voltages, and have fairly high transconductance for low output impedance, and good enough u to make a good follower.

Sheldon
 
D

DualTriode

Member
Joined 2009
Bengali said:
Thanks DT.

I appreciate the great feedback. I will try one.

What's your preference for power supply with the BCF?

Which tubes did you decide on?

I will keep an eye out for the RCA NOS tubes.
Click to expand...

Hello,
For a power supply I like to use PS-2 Solo, sometimes a point to point home brew, the one I am using with the ACF in the headphone amplifier I bought from John. The voltage is set at 250 volts. The tubes were selected from stock on hand, Sylvania 6BQ7A.
DT
All just for Fun!
 
S

Sheldon

Member
Joined 2003
Are you doing a BCF or an Aikido CF? Here's what I'm using after my
phono amp. The cathode resistors are sized for about 80% of max power (2W total for both triodes).
 

Attachments

  • Aikido follower.GIF
    Aikido follower.GIF
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D

DualTriode

Member
Joined 2009
Bengali said:
Hi DT,

What values should I use for C6 and C9 for BCF?

just got a nos pair of 6dj8 amperex and will try those for the BCF.
was planning to get one of JB's psu pcb's along with the BCF.

thanks.

Hi Joachim,

I will take a look at your circuit. Thx!
Click to expand...

Hello Bengali,
For both C6 and C9 I used Wima MKP 10 0.68 uf. The ACF user manual has good discussion for selecting capacitor values. John provides a formula for C6, This formula produces a minimum recommended value.
BTW In my first post I lost focus and typed BCF by mistake, all my references here are to the Aikido Cathode Follower, ACF
DT
All just for Fun!
 
B

Bengali

Member
Joined 2006
Hello Bengali,
For both C6 and C9 I used Wima MKP 10 0.68 uf. The ACF user manual has good discussion for selecting capacitor values. John provides a formula for C6, This formula produces a minimum recommended value.
BTW In my first post I lost focus and typed BCF by mistake, all my references here are to the Aikido Cathode Follower, ACF
DT
All just for Fun!
Click to expand...

for 6DJ8, I'm using the values in the manual.

R8= 3480
R9= 100000

C6 = 318310/(R9 + R8)/60

I'm getting 184.56 for C6. does not look right.

He recommends 200V for 6dj8 tubes, any ideas why? If I make it 250V,
I could then try other tubes, 6cg7 with some resistor value changes.

thanks!
 
D

DualTriode

Member
Joined 2009
Bengali said:
stupid of me to assume, I thought BCF is same as ACF.
what does the 'B' stand for?

I'm going to build the aikido CF since JB has new boards out.
C6 and C9 can be up to 1uF so I'm curious what you are using and why.


thanks
Click to expand...


Hello Bengali,
Why both C6 and C9 are Wima MKP 10 0.68 uf? They came with the PCB. They could be up graded to paper in oil or you pick another style. If I thought that there was an issue I would have swapped them out for an upgrade. So far I do not think they are broke.(If it ain’t broke don’t fix it.)
Just for grins I used Partsexpress http://www.parts-express.com/catalog/pdf/2010/159pec10.pdf part #027-458 Polypropylene Film and Tin-Foil 0.47 uf for output capacitors. I thought that I would give them a try. I think that they sound pretty decent, at $1.47 they are a great buy. Use boutique parts if you like.
BCF is Broskie Cathode Follower. See The current Tubecad.com blog.
DT
All just for Fun!
 
D

DualTriode

Member
Joined 2009
Bengali said:
for 6DJ8, I'm using the values in the manual.

R8= 3480
R9= 100000

C6 = 318310/(R9 + R8)/60

I'm getting 184.56 for C6. does not look right.

He recommends 200V for 6dj8 tubes, any ideas why? If I make it 250V,
I could then try other tubes, 6cg7 with some resistor value changes.

thanks!
Click to expand...
Hello Bengali,
This how I did the math:
uf = 318310/(R9+R9)/60
318310/(100000+3480) = 3.076 3.076/60 = 0.051 uf
It depends how you punch the casio keys.
My thoughts about the 200 B+ voltage for the 6DJ8. I could be the straw man, I am not John. The lower the B+ the lower the value of the cathode resistor can be, the lower the value of the cathode resistor and the lower the Rp (internal resistance of the tube) the lower the output impedance (Zo) of the completed circuit. The listed Zo for the 6CG7 is higher than the value listed for the 6DJ8, both are very low for a line stage. Driving headphones is another story. Check out the table in the user manual. Voltage and tubes; your choise.
BTW
One of my hand wired ACF uses 6BK7’s with 57 ohm cathode resistors the Zo is 167 ohms. With para-feed through a Edcor impedance matching transformers (15000 : 600) to 300 ohm headphones the amplifier see the headphones as 7 ohms, there is a very high dampening ratio here, no flabby bass. Sounds good to me!
DT
All just for Fun!
 
B

Bengali

Member
Joined 2006
Hello Bengali,
This how I did the math:
uf = 318310/(R9+R9)/60
318310/(100000+3480) = 3.076 3.076/60 = 0.051 uf
It depends how you punch the casio keys.
My thoughts about the 200 B+ voltage for the 6DJ8. I could be the straw man, I am not John. The lower the B+ the lower the value of the cathode resistor can be, the lower the value of the cathode resistor and the lower the Rp (internal resistance of the tube) the lower the output impedance (Zo) of the completed circuit. The listed Zo for the 6CG7 is higher than the value listed for the 6DJ8, both are very low for a line stage. Driving headphones is another story. Check out the table in the user manual. Voltage and tubes; your choise.
BTW
Click to expand...

probably will do something so that's it's not fixed for one set of tubes.



One of my hand wired ACF uses 6BK7’s with 57 ohm cathode resistors the Zo is 167 ohms. With para-feed through a Edcor impedance matching transformers (15000 : 600) to 300 ohm headphones the amplifier see the headphones as 7 ohms, there is a very high dampening ratio here, no flabby bass. Sounds good to me!
DT
All just for Fun!
Click to expand...

very nice!

Thanks again for your help! :)
 
Einric

Einric

Member
Joined 2011
Paid Member
I picked up a matched quad of Sylvania 6CG7's on ebay for $35.
Keep an eye out for the ones with the shield between the triodes.
If it is there it's a 6CG7 if it's not it is a 6FQ7.
You want the shield.
I have my quad running in an Aikido All In One and they are FANTASTIC.
I tried some Matched JAN Sylvania 6DJ8's and didn't really like their midbass performance.
 
Gost22

Gost22

Banned
Joined 2012
Aikido Cathode phollower with 12au7

Joachim Gerhard said:
I build this. It sounds great. Very dynamic and wideband and totally quiet.
I have shown the tubes as Fets because my editor can not draw them.
It runs on ca.7mA idle and the tubes get a bit hot. Next time i reduce to 6mA by raising the cathode resistor values.
Click to expand...
Hi Joachim!
I made ​​the cathode followe with tube 12AX7. I connected this the cathode followe between my CD-player and audio amplifier F5. I was very pleased with the sound!:up::eguitar::violin: A great definition! I used Ecc83JJ - Slovak and 12ax7 Chinese production without label. This tube of Chinese made, plays better sound to my taste!;)
Otherwise, I want to make and the cathode followe with your ECC82 (12AU7) to hear how it sounds.
Give the value of resistors for current from 6mA?:confused:
Here arranged thy schematic with ECC82;):)
Thanks and cheers!:cheers:
 

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  • Cathode follower with 12au7.pdf
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Last edited:
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