diytube.com

This is a great concept. A 6BM8 drives the 845 beast. It is so obvious. Hard to believe it is not in greater use.

volt amp -> power pentode -> 845

AC on the filaments with a hum pot would simplify this design even further. The voltage doubler with a standby earns more points. Variable NFB, too.





I wonder about this design with an 813...

Use hi gain "video" pentode (gm = 40000 ) and you'll no longer need more than one stage !



Yves.

The schematic below is too big for the forum.

EL803S (triode strapped) -> EL86 (triode strapped) -> 845

B+ = 770Vdc

http://www.jogis-roehrenbude.de/Leserbr ... lan845.jpg

I was considering a 6EM7 or 6DN7 SET, with the power triode's plate loaded witn a MQ BCP-15 choke, then cap-coupled to the 845's grid.

Actually this was my original plan for driving a GM70 SET, but it should work on 845s or 211s just as well. I ended up passing along my ideas and some parts to Gary Kaufman, who also was planning a GM70 project.

I like to keep my B+ 600VDC or less....

/ed B

kheper wrote:The schematic below is too big for the forum.

EL803S (triode strapped) -> EL86 (triode strapped) -> 845

B+ = 770Vdc

http://www.jogis-roehrenbude.de/Leserbr ... lan845.jpg

The link to the image above is broken, so I re-linked it.

http://nekhbet.com/Schaltplan845.jpg