diytube.com

Gents,
I have been thinking that I'd like to give the MKIII a try. That said, I see that dynakitparts offers a complete kit; but I'd rather use shannon's board and modify my BOM to my liking. Additionally, I think I may try some edcor OPTs (Anyone ?). Any other suggestions for the build ? I think I may just go with a plain chassis and punch as necessary.
One other thing I was thinking about would be subbing in a 6SN7 in the place of the first 12ax7; any thoughts ?

Thanks !
Steve

If you want to sub an octal for the 12AX7, use a 6SF5. The 6SN7 just doesn't have the gain needed to drive the 12AU7/KT88 configuration. (It would work great with 6BQ5 outputs.) You could also use half of a 6SL7 or 5691 and a 6SN7 in place of the 12AU7 if you wanted an all glass octal tube complement.

FWIW, my personal choice would be: 6AT6 --> 12BH7 --> KT88s, which is what I used in a prototype almost identical to Shannon's design (no CCS in mine) that I developed back in 1999--and everybody said it wouldn't sell.

Hey Eric,

I don't recall you mentioning the 6AT6 before. I must have been asleep if you did. Looks about like half of a 5751 with a couple of diodes on the side. Care to talk about that one for a bit?

Hi Ed,

I might have let that cat out of the bag before you joined the forum. Yep, the highly touted (and deservedly so) 5751 is nothing more than a matched pair of 6AT6s with slightly beefier heaters, hold the diodes. The 6AQ6 is the 'AT6's twin, and 9 pin versions of it can be found in the 6CN7 and the 6T8 family. Octal siblings are the 6AQ7 and dual triodes 6SL7 and 5691--I can't call them twins because their transconductance and plate resistance values are slightly different, but RCA considers them sufficiently alike so as to include them in the same RC amplifier chart.

My experience with 6AQ7s is that they tend to be photosensitive--don't use them around conventional fluorescent lights unless you put a can over them; they hum.

Eric,
Thanks for the heads up...Sounds interesting for sure.....We'll see what I dig up :D
In my EL84 amp I am running the 5151->12BH7; I like 'em !

-Steve