Took a leaf out of Graydon's book (or was it more like half the book) and studied the Vox AC30 circuit more closely. I added two more 100 ohm 5W grid resistors giving each EL84 it's own. I have left the cathode resistors as they were, two 150 ohms, one to each pair of EL84s.
Cured all the screeching and tizzing.
It's based on the MV/TMB and has none of the high pitched whistling you can sometimes get, that's down to following Jersey Aarons earthing layout to the letter.
Graydon is right, loads more clean headroom, the ordinary channel is very powerful. Literally power you can feel in your body. The MV channel doesn't break up easily, perhaps a few more value tweaks there. It is not possible to turn it up full in the house, it is just too damned loud. I will wait until it rains hard, lock the beast in a room and take the guitar outside the door to see how loud it will go. At the moment I wouldn't be able to stay in the room with it turned up full.
I would say it is fuller, with more body and just feels and sounds more ' powerful ' not just louder, but almost startling in it's power.
Not suprisingly you can still hear the 18 watt character in there. I will build another with a 30 watt Vox AC30 OT to see if it breaks up quicker. At the moment I have a Hammond 60 watt OT in there as it is the only Hammond around 4K primary impedance.
Steve UK
