Aikido Phono Stage

[rhcclark]

Hi
I have a stereo 5687 Aikido board and would like to build a phono stage around it. Has anyone done this or know of any circuits for it? If not any thoughts as to whether it would even work? Never attempted a phono stage before.

thanks in advance

Bob

[JoshK]

john broskie has done a little more than ellude to this. basically you will need two aikido stages with the riaa correction between the stages. 5687 should work well for the followers but you will likely need much higher gain tubes for the first spots.

he mentioned that someone at a europeans diy fest got first prize for an aikido phono. so its been done before.

[Tweeker]

5751 would be a candidate for the first Aikido section.

Tubecad passive RIAA article.

Fourth time constant note.

[jduffy]

Correct me if I'm wrong, but if you use two boards don't you then need eight tubes?

[JoshK]

yep

[Sheldon]

I did something like this. If you look at the last three triode sections, you will see that they are an Aikido amp with a single triode as the first section. http://www.diyaudio.com/forums/showt...67#post1170667

There's no reason you couldn't use your board and both triode sections, instead of the single triode and cathode resistor. You'd just have to calculate the Rp of the top section.

For the front end, you could use a 6922 cascode, or a hybrid cascode like this:
http://www.diyaudio.com/forums/showt...687#post959687

Sheldon

[rhcclark]

Thanks for the responses. Tweaker I read the passive riaa link and Sheldon I have to review your circuit more closely. Wow this is significanly harder than a line stage or a little SE amp! I have to digest all the Bronski stuff to many variables in there and to many things I dont know. Im going to just be running high output ("high output thats a laugh") MM cartridges with it so that should help. Sheldon what kind of accuracy where you able to achieve and how hard is the eq to tweak.

[Sheldon]

Originally posted by rhcclark
Thanks for the responses. Tweaker I read the passive riaa link and Sheldon I have to review your circuit more closely. Wow this is significanly harder than a line stage or a little SE amp! I have to digest all the Bronski stuff to many variables in there and to many things I dont know. Im going to just be running high output ("high output thats a laugh") MM cartridges with it so that should help. Sheldon what kind of accuracy where you able to achieve and how hard is the eq to tweak.

It is a bit complicated, but it's manageable. I can help you calculate your eq values and many of the experienced people here are very willing to offer help and advise. If I get the chance, I'll make up a circuit example in the next couple of days.

I built a reverse RIAA circuit don't have the citation with me, but will dig it up when I get home next week. With no changes to my calculated values, I was able to get within a couple tenths of a dB from 40-20kHz. And that was including the step up transformer. It was more than 0.2 off only at the extremes. So I didn't do any tweaking, though it's not hard to add a bit of capacitance or change resistor values. You are welcome to borrow the reverse thingy when you get to that point.

This calculator is much help: http://www.hagtech.com/equalization.html

Sheldon

[Bruce Anderson]

Charlie Butterworth is coming over this weekend to show off his (AT LAST!) totally quiet Aikido and compare it to my full function (yes, EIGHT tubes!) Aikido. (ECC85, 6DJ8, 6SL7, 6SN7) Maybe he will feel like giving his impressions.

[Sheldon]

Here's what an Aikido phono amp might look like with a cascode front end.