I recently completed a Cornet 2 for an audio buddy of mine (he is not a DIYer), and made a few modifications that may be worth others trying on the stock Cornet 2.
First, I added a pair of 15H Hammond chokes (155J) in place of R220. You may have to adjust the value of R221 to suit (the choke has a resistance of about 1K versus the 1.8K resistor value). I mounted these as far away from the power transformer as possible.
Second, I modified V3 to permit using 6CG7/6N1P/6N6 tube instead of a 12AU7. This can be easily accomplished by lifting either pin 4 or pin 5 on the tube socket from the main board, bending the pin and soldering a short wire to pin 9, while insulting the pin with a bit of 1/8" heatshrink (to prevent contact with the pin 4/5 board connection). Also need to adjust the heater drop resistor because of the additional current draw, I am using 1.0 ohm.
Also, and as noted elsewhere on this forum for the 6CG7/6SN7 mod, change the resistor value for R218 from 910 ohms to 560 ohms to increase the current through the follower section.
The result is a output stage that has alot of drive and solidity. Very easy to find good sounding tubes for V3, I really prefer the Russian 6N6 here, though it is a matter of taste.
I should also note that I am using V-caps teflons for C203, and V-Caps OIMP for C208. These are just superb sounding, with a transparency and fullness that is beguiling.
I would like to personally thank Jim Hagerman for a design that is so simple, yet tweakable to such an excellent result. I have also built an Octal Cornet from scratch with a shunt regulated supply, and also find this to be dead quiet, musical, and throughly enjoyable to listen to.
