Going for something slightly different...

[SteveH]

All,
So I was thinking. Why not use this driver board, and make a nice dual-mono 807 amp ? Just need to do a little tweeking for the plate loads, etc...Should be possible though eh ?
Anyone tried this before ?

[SteveH]

Guess not ?

[Blair]

A stereo version of the Poseidon? I'm doing this right now with the help of a few much better qualified people than me.


http://img.villagephotos.com/p/2005-12/ ... /AMP_5.JPG



Blair

[mesherm]

I have not used 807s but I have used 6BG6Gs in place of EL34s and they worked quite well.

[SteveH]

Thanks !
I am going to order the boards later this evening and think about how I want to go about this.
My aim will be for about 40wpc or so; have to do up the loadline and see what I can come up with.
I suppose my main concern would be oscillations, as I know the 807's love to. I'll calculate out the grid resistor and see what value comes up. Any suggestions for an off the top of your head value ?

Thanks,
Steve

[Shannon Parks]

Steve, go ahead and search the forums for "807". There have been several threads touching on this PP scheme. My friend Thermion used my ST70 driver in a ST70 with 1650N outputs and 807s. Feedback network is stock, though I assume it needs tweaked. He loves it. Total power isn't what the datasheets show, though. I think he was about 20W at 1%THD.

[SteveH]

Shannon,
Thanks ! I really would like to get 40wpc out of it, hopefully that will be possible ? I don't know how to establish load lines for PP amps, so I need to read up on that first. Then I guess I'd have a better understanding of what modifications I need to do to the circuit.

Thanks !

Edit - In looking around, it seems like the Edcor OPTs are the way to go. I just bought a pair to use in a compactron project I am working on (pics in about a week :D ). They really do seem like rather high quality.

[miker]

It looks like you may be able to get that kind of power in class AB1 with about 500 volts on the plates. Take a look at the RCA data sheet for 807..

http://www.mif.pg.gda.pl/homepages/frank/sheets/084/8/807.pdf

I'm planning to build a version that will accept KT66 or 6L6 tubes. I have a pair of Acrosound 6.6k U/L transformers for the job. Maybe with a socket adapter, I could run 807's also.

[kheper]

SteveH

Do not forget that the max screen grid
voltage of an 807 is 300V. You'll need
to chop the voltage down coming from
out of the screen tap. Parallelling 2W
carbon comp resistors is one way to
go. Metal film resistors will catch fire!
You'll need 10-20W clearence on
the total wattage rating. There are
some nice wirewound, aluminium-
housed, non-inductive 25W power
resistors which look attractive. They
go for $5 a piece.