I don't have any problem with notes dying fast. I find there is huge difference in sustain that depends on the PUs (especially when unpotted) and guitar. Does your sustain depend on where you set the presence control? If so, check the value of the 100k feedback divider resistor.tubedogsmith wrote:Ron, I know this isn't your first rodeo. Do you have any trouble with notes dying fast with it cranked? Have you scoped it by any chance? Running the presence wire through the filament wires and having the grid wires in proximity to all that just never worked right for me. Maybe I need more patience.
I always run the presence-feedback wire next to the chassis (ground) and directly between the speaker jack (or switch) and the phase inverter (don't run it around the chassis).
Crossing filament wires is OKay if they are twisted; the reason for the twist is to get cancellation between current elements that could induce a hum or other signal.
There are two kinds of grid wires and I'm not sure which you are asking about. One is just screen bias to the output tubes through the 1k/5W resistors, and those wires are at signal ground through their filter caps. The other is the guitar signal from the phase inverter. The latter are flying leads that are far enough away from other leads to avoid problems.
PS I just plugged in, turned the amp to about 1 o'clock and stood across the room facing away from the 4-12 to avoid feedback. I confirmed that the notes easily sustain themselves without string or PU feedback.
PPS One suggestion re the note sustain problem: check your power supply! At high volume the amp needs more stored energy and yours may have a problem with a filter cap. Make sure the caps supplying the CT of the OT are connected directly to the diode bridge. Any resistor in there will delay resupplying energy to these caps.
