boola wrote:So the consencus is that ghost notes happen and there aint too much that can be done about it....
bwplexi wrote:A stiffer choke may help also.
Ogoki wrote:After a lot of experimenting, I have accepted that ghost notes are really a fact of life with these amps.
A while back I messed around with a few stiffer chokes from Hammond. They really didn't do much for the ghosting and gave the amp an unfocused feel which made me pull them right away. I ended up with the original choke back in place and extra holes in my chassis.
I often go with 1.5k or 2k screen grid resistors, which should limit current to the screens a little. Bumping the screens filters to a pair of 60 or 68uF can also help a little and retain a pretty stock feel. Again, these tweaks only help a little with ghosting...
Chris brings up a really important point about one side of the PI driving harder than the other. I have started paying a lot of attention to this after witnessing some xf2s redplating at very modest biasing settings under hard playing. I played around with various power tubes and always got redplating on the two power tubes driven by the 82k side of the PI. (Believe or not, the RFTs wouldn't replate when Mullard, Amperex and Roznov Tesla EL34s would!) In short, the plate load is too low and the voltages are too high. Simply running a one-step upward mismatch (i.e. amp on 8ohms with a 16ohm cab) should make things more bearable for the power tubes. Raising the value of the PI tail resistor (e.g. from 10k to 27k) also helps. And, run your power tubes which draw less current in the two slots closest to the preamp.
Users browsing this forum: Google Adsense [Bot] and 8 guests