Joe

j_armocida (at) yahoo.com

Am I correct in assuming that you are looking into driving cathodes and perhaps AB2 or A2 (grounded grid) operation? If that is so, can you elaborate on the why's other than a linear input Z to the cathode as the transistion is made to drawing grid (G1) current?

I trust you got my email and will favor me with a reply. The attachment I got from from the person of interest was removed by my work's filter system (and I'm not sure he feels like sending it a third time:(. So please, no attachments and no (4 letter) words that would offend a catholic nun or I won't see it.

Russ
P.S. Can we chat at vintage?

I am not certain that the cathode drive has merit. Perhaps for a more ocnventional design, but I think I have a bit of research and experimentation to do first. I also think 70W from a pair of E-Linear rigged 813's will be of higher quality than a cathode driven pair of 211's ( not to mention more powerful and lower output Z ). As proof of reasonable potential, I keep comming back to the 813's.

I have heard the arguement that they don't like U-L connection, but I figure if they can survive as triodes, I can run them U-L/E-L

I did favour you with a reply to your note. I am not sure what you meant by 'chat at vintage'...
regards,
Douglas

I too feel that cathode drive is not the way to go for your purposes. I only see it as a plus for UHF/VHF stuff. It puts the entire cathode AC current in series with the driver circuit (out of phase at that which is part of why it's more linear) and ends up netting less power than G1 drive (darn near 50% less depending upon type of tube and class of operation). I think 813's in UL have potential or I would not of mentioned same (but feel tertiary windings for G2 are needed). I do think they will present some "problems" but feel you would enjoy the work. I would look towards perserving a voltage between G2 and anode based upon the physical spacing of these elements and feel that the common practice of operating G2 at a higher voltage than anode was only done for certain tubes in the hi-fi wattage race and not in the interest of good sound (or reliable operation).

If you don't have it, Eimac's "care and feeding of power grid tubes" is worth looking at for high voltage transmitting stuff. If I run across a copy I'll send it your way. I shall certainly miss you over yonder and pray you will return soon.

Russ
P.S. I'd like to hear about your new job and where you will be located....always looking for a good M.E. (mostly HVAC related) for work's projects.