Aikido Cathode Follwer Question

[needtubes]

Hello all-

I am thinking about adding a tube preamp/buffer to my current all-SS system. Since I already have more than enough drive from my DAC, I think the ACF will be sufficient for my purposes. I am just a bit lost when choosing certain parts...

For one, I cannot seem to decide on a power supply. I am somewhat torn between the PS-1 and Janus Shunt Regulator offered by Glass-Ware. Which of these would be the better choice keeping in mind that I want to minimize distortion and noise and maximize neutrality of sound? I am leaning toward the Janus, but need more experienced opinions.

Now, assuming I have settled on a power supply, I am looking at Antek's toroidal power transformers. I am at a loss as to which transformer I need... My plan is to use a pair of JJ ECC88/6922 tubes in the ACF, which I think should be run at 200-250V to be happiest. Correct? In this case, do I need something like Antek's 2x150V transformer?

I am sure I'll have more questions as the build progresses... But, I must first order the parts!

Any help is much appreciated!

[DF96]

As I understand it, the whole point of the Aikido is that the two stages together draw constant current from the supply. Therefore as soon as you separate the CF, it is no longer an Aikido or half an Aikido or the back end of an Aikido, but an ex-Aikido: just a CF with an active load.

The whole point of a CF with an active load is that it passes the signal with unity gain and very low distortion, so you don't hear the CF but just the music. If done properly it will therefore do nothing to a system except add a little noise, probably too little to notice. Is that what you are looking for? If you are looking for a tube buffer effects box, then you want a badly biased CF without an active load, so it adds distortion to the signal.

[leadbelly]

Originally Posted by DF96

As I understand it, the whole point of the Aikido is that the two stages together draw constant current from the supply. Therefore as soon as you separate the CF, it is no longer an Aikido or half an Aikido or the back end of an Aikido, but an ex-Aikido: just a CF with an active load.

The whole point of a CF with an active load is that it passes the signal with unity gain and very low distortion, so you don't hear the CF but just the music. If done properly it will therefore do nothing to a system except add a little noise, probably too little to notice. Is that what you are looking for? If you are looking for a tube buffer effects box, then you want a badly biased CF without an active load, so it adds distortion to the signal.

You missed the boat completely. He's just asking for advice about this: Aikido Cathode Follower & More Triadtron

[syyma]

I breadboarded the ACF and currently use in my garage. I separated the PS-1 in two small breadboard. I've tried 6BK7, 6BQ7, 6BS8, 6CG7, 6N1P, 6922 and 12AU7 all with good result. I don't have a scope to measure the power supply noise but dead quiet. Hope that help your ACF build.

[DualTriode]

Originally Posted by needtubes

Hello all-

I am thinking about adding a tube preamp/buffer to my current all-SS system. Since I already have more than enough drive from my DAC, I think the ACF will be sufficient for my purposes. I am just a bit lost when choosing certain parts...

For one, I cannot seem to decide on a power supply. I am somewhat torn between the PS-1 and Janus Shunt Regulator offered by Glass-Ware. Which of these would be the better choice keeping in mind that I want to minimize distortion and noise and maximize neutrality of sound? I am leaning toward the Janus, but need more experienced opinions.

Now, assuming I have settled on a power supply, I am looking at Antek's toroidal power transformers. I am at a loss as to which transformer I need... My plan is to use a pair of JJ ECC88/6922 tubes in the ACF, which I think should be run at 200-250V to be happiest. Correct? In this case, do I need something like Antek's 2x150V transformer?

I am sure I'll have more questions as the build progresses... But, I must first order the parts!

Any help is much appreciated!

Hello,
I can address some of your questions. I use an Aikido Cathode Follower daily. The regular Aikido has too much gain for my taste. The ACF with a stepped attenuator makes an excellent line stage with a gain of near one. Speaking of the Regular Aikido the ACF stage does not invert the signal and draws current in phase with the input. There is no offsetting current balance between the stages of the amplifier. The ACF has low output impedance to drive long interconnects and hungry loads at low distortion. The bottom triode is in counter phase that is where a portion of the B+ noise, if any, is injected Janus style to increase the PSRR.
I am happy with the PS-1. An interesting thing is that Janus is not a voltage regulator per say. You cannot select part values to set the output voltage, although it does greatly improve the PSRR of the amplifier that it serves.
The 6922's have a recommended maximum plate voltage of 135. With the triodes in series 200 to 250 volts B+ is good. Check out the User Manual for recommended part values.
DT
All just for fun!

[DF96]

You missed the boat completely.

Yes, sorry. I didn't realise that there are now two completely different circuits both called Aikido.

[jgf]

I'm using an ACF also, with 6CG7 tubes. At first I built it with SS bridge --> CLCRC supply. I was seeing some power supply output voltage fluctuation, which also appeared on the audio output (tens up to 100 or so mV), enough to affect the power amp bias.

I put it on the scope, voltage looked fairly constant, except occasional jumps, then settle. I guess it's caused by line voltage fluctuations. Output caps are 1uf, into 220k or so giving corner freq of 0.7hz or so. I tried .22uf caps, but the problem didn't really go away.

So I try Janus reg and PS-1 reg. Janus reg improves sound, nice and airy and 3-D, but doesn't solve low freq problem (as Broskie wrote, not a surprise.) PS-1 reg does solve DC voltage, and sounds solid top to bottom.

The only thing I didn't try was a tube rectifier (not enough space or voltage available from transformer), does anyone know if that would buffer line voltage variation?

Now I need to solve the fuse blowing issue, big 150uf cap inrush blows the 1amp fuse.
I'll probably go with a timer circuit and a current limiting resistor at startup.

[PWR RYD]

I'm interested in building this preamp circuit as well. I will use a pair of 6DJ8's that I have. I would also like to know how a tube rectifier power supply would affect performance. I have a 5U4GB rectifier already. Would this with the properly sized transformer and CRCRC filter make any audible improvement?

[PWR RYD]

Edit: the 5U4GB is probably way too big. How about a 6x4?

[jgf]

I did PSUD simulations with 6x4 for a preamp around 20ma, I was PIV error at startup, but maybe could be made to work. 6ca4 and 5y3gt are in between 6x4 and 5u4 for current handling.