My New Aikido Cathode Follower Preamp

Ali Tait · Post by **Ali Tait** » Sun Aug 25, 2013 8:33 pm

Aye, PM'd you too.

pre65 · Post by **pre65** » Sun Aug 25, 2013 8:36 pm

And me.

simon · Post by **simon** » Sun Aug 25, 2013 10:07 pm

David wrote:The Aikido circuit file is too big to upload but I will happily e mail it to anyone interested. Greg, you have it unless you've changed e mail.

I've just noticed I have the manual for the original ACF stored on my hard drive - this has the original circuit, descriptions, suggested valves and values, power supply notes etc. etc. Don't know if this is what you're referring to David, albeit version 2, but I can email my copy of the original to anyone that's interested.

David · Post by **David** » Mon Aug 26, 2013 9:24 am

Hi Guys,
I'm not getting pm's or e mail notifications for some reason. I will have a look in settings otherwise any ideas anyone?
David

David · Post by **David** » Mon Aug 26, 2013 9:27 am

Hi All,
They've arrived. Maybe slow as im in Greece........
David

pre65 · Post by **pre65** » Mon Aug 26, 2013 10:55 am

I've got details from Simon and David (thanks guys).

One thing I notice is the (optional) cathode bypass capacitor is listed as 1uK @ 16v.

Whats a uK ?

Also, the two lists differ on the value of R9. Simons list says 100K and Davids list says 200K , and R8 is different as well on each list.

Just initial observations.

Ali Tait · Post by **Ali Tait** » Mon Aug 26, 2013 10:58 am

Simon's is an older version I think?

IslandPink · Post by **IslandPink** » Mon Aug 26, 2013 11:07 am

Ali Tait wrote:John Broskie seems to favour the ECC99 -
http://www.tubecad.com/2011/01/blog0198.htm
I've ordered one to have a go with.

I tried them years ago as the first option in the Aurora PP driver stage . I found them somewhat hard and 'toppy' . The RCA 5687 was much better and more transparent . Then I moved to 6N6P's, liked these even more ( but that could be because the sections are are not well matched and I got a bit more 2nd-harmonic in the PP stage ) .
Anyway, don't spend on ECC99's until you've tried ordinary 1980's 6N6Ps first.
Sorry Ali - too late !

pre65 · Post by **pre65** » Mon Aug 26, 2013 11:41 am

Just been looking through my valve stock to see what is available.

I've got a pair of 6N2P-EV, which seem to be alternatives to 12AX7 / ECC83.

Are these still thought of as "good" ?

Ali Tait · Post by **Ali Tait** » Mon Aug 26, 2013 11:55 am

IslandPink wrote:
Ali Tait wrote:John Broskie seems to favour the ECC99 -
http://www.tubecad.com/2011/01/blog0198.htm
I've ordered one to have a go with.
I tried them years ago as the first option in the Aurora PP driver stage . I found them somewhat hard and 'toppy' . The RCA 5687 was much better and more transparent . Then I moved to 6N6P's, liked these even more ( but that could be because the sections are are not well matched and I got a bit more 2nd-harmonic in the PP stage ) .
Anyway, don't spend on ECC99's until you've tried ordinary 1980's 6N6Ps first.
Sorry Ali - too late !

No, not at all, just meant I'd ordered a board. I already had a pair of 99's which I used to use on that 813 amp I got from Andrew. I found the same as you, a bit toppy. Otherwise very good though.

I've plenty valves to try in this, some nice 88's, and some very nice (and expensive!) 82's. Loads of 6n6p too.

pre65 · Post by **pre65** » Mon Aug 26, 2013 12:18 pm

OR.

I see the 6CG7 is an option, and from memory that is a 9 pin 6SN7. So I could use 6SN7 (Russian) and octal relay bases.

colin.hepburn · Post by **colin.hepburn** » Mon Aug 26, 2013 1:48 pm

David wrote:Hi All,
They've arrived. Maybe slow as im in Greece........
David

Received it went in to my junk box

Thanks you David

pre65 · Post by **pre65** » Mon Aug 26, 2013 3:03 pm

pre65 wrote:OR.

I see the 6CG7 is an option, and from memory that is a 9 pin 6SN7. So I could use 6SN7 (Russian) and octal relay bases.

Don't take any details on that "typical part values" sheet as gospel without checking.

On the 6CG7 data the heater voltage is 6.3v @ 0.6A with NO 12.6v option, not as per the sheet.

I have got two 6CG7 as well, so I have 3 options (from stock box) now.

6CG7 or 6SN7 or 6N2P-EV

IslandPink · Post by **IslandPink** » Mon Aug 26, 2013 4:51 pm

pre65 wrote: I've got a pair of 6N2P-EV, which seem to be alternatives to 12AX7 / ECC83.
Are these still thought of as "good" ?

James should be able to tell you, Phil . I had a bag of them from Dave Dove, but James bought them off me, I never tried them . Certainly they are handy for Aikidos as you need something with good performance and plenty of gain for the first stage, so 5751's and perhaps 6N2P would be good . If you can make an Aikido with octal first stage, then 6SL7's are the obvious choice.

pre65 · Post by **pre65** » Mon Aug 26, 2013 4:55 pm

Ah yes, but I'm thinking of the CF option, with no gain, but plenty of drive.

audio-talk

My New Aikido Cathode Follower Preamp

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