[Ivan303]

REALLY like your Cornet design.  No cathode bypass caps anywhere!

Also, heard it at VSAC and was Mucho Impressedo.

Have downloaded both the 12A* and 6S* version of the schematics, and have a question about the cathode voltage on the cathode follower.

Isn't that a bit high with the heaters tied to ground?

Silly me, I can't remember what the heater to cathode max rating is on either a 6SN7 or a 12AU7, but I do have the heaters referenced to a higher volage than ground on my SRPP driver tube on my 300B power amps for that reason.

The Cornet sounded great at VSAC with 9 pin wonders, can't imagin how good it would sound with NOS 6SL/6SN type tubes.

Heck, bet it would even sound great with Loctal's

[hagtech]

Yes, it is high.  But within specs if you use the right tube.  And that's why I chose a 12AU7.  Specified at 180V Vkh.  The 6SN7 is even better, I believe.

So far, no problems reported.  I typically like to give myself a bit more headroom when it comes to these sorts of limits, but once in awhile you find yourself in a compromising position.  Another example is the reverse breakdown voltage of the UF4007 diodes in the Trumpet - the signal gets to about 90% of ratings.  I tested a number of devices and they came out way higher than spec.  Not that that is an excuse, just some comfort.  

Design involves so many compromises.  You just have to go in circles a lot until you find an optimal solution (each designer is different).  It's art mixed with science.  A perfect amplifier would just plain cost WAY too much.

jh

[Ivan303]

Thanks Jim.

According to the RCA tube manual that was sitting just a few feet away from me as I posted the question...

6SN7GTB Heater Cathode Voltage
Peak Value =/- 200 V max
Average Value 100 V max

12AX7 is the same.