Akita 12V preamp thoughts

[prezden]

Does anyone have any experience with the new Akita 12V preamp? I am thinking of using with a Peter Daniels LM3875 chip amp.

New Aikido 12Vac PCB and part kits

 

[CijTele52]

I don't have experience with the Aikido 12V because John told me he was working on Aikido 24 that take 24VAC. Now it's 12V which I think it's brilliant!

 

[prezden]

Nobody: wave2:

 

[Sodacose]

I'm actually at looking to do exactly the same thing (Aikido 12VAC w/ LM3875 Gainclone) with the addition of an integrated Bugle2 phono preamp. Did this project ever come about for you?

 

[tinitus]

thought I just now read it uses 18V trafo ?

edit ... different tube

 

[Sodacose]

18V on the 12AU7 option so your comprehension is only slightly impaired

 

[prezden]

I think there are 2 options- 12v and 18v

 

[tomlang]

I'm upsizing to 24vac that should yield about 180vdc.

http://www.diyaudio.com/forums/tubes-valves/235901-aikido-12vac-2.html#post3603908

 

[prezden]

tomlang- thanks for posting the link

 

[tinitus]

how about the heaters ?

Broskie often couple tubes in parallel or series to match the voltage on hand

 

[tomlang]

The heaters are depicted on the schematic below as four 74 ohm resistors in series with a 68 ohm dropping resistor. Simulation shows 2 watts being dissipated in the 68 ohm resistor.

With the 18vac version, there is a 10 ohm resistor and barely enough voltage on the 12.6v heaters.

As far as the aikido circuit itself, you will want to change cathode resistors to shift the operating points.

 

[tinitus]

ah, yes, I see it now ... Rfill*

I guess voltage is coming in between C8 and C9 ?

 

[tomlang]

Filament voltage derived from the spot I marked "X" and the negative voltage probe (black colored) shown below with ripple expected. 68 ohms drops it to about 48vac across the 4 series filaments with even less ripple due to the RC filter of R11 and C10.http://www.tubecad.com/2013/03/blog0258.htm

For an in-depth review from the designer himself of this sextupler circuit, refer to his blog:
http://www.tubecad.com/2013/03/blog0258.htm

 

[Sodacose]

Anyone know which tube/voltage option would play better with a Gainclone amp? 6DJ8's provide a gain of 15db, 12AU7's a gain of 9db. I believe the Gainclone chips all run at a minimum gain of 10db?

I was thinking about 6DJ8's @ 15db and a LM3886 @ 15db for a total of 30db. Too much for an 'integrated'? Am I missing something about how these would interact?

Tubecad 12VAC article if everyone hasn't already found it.