Tranny and tube locations, PS caps and pot locations are different than the express layouts show. One problem was major parasitic oscellations.
So I made the following changes to the layout. V1 uses only half the tube and both halves of V2 are used. This amp is very quiet for such a high gain amp. One problem I still have is a high pitched whine that is controlled by the presence pot. Turn the pot to 0 and the noise goes away. I mounted the 100k feedback resistor on the output jack, lower signal level going to the PI should help with noise. Does anyone have any ideas as to the cause/cure?
This amp sounds great. It is not a express clone due to the output trannys impedance. I measured it at 5k, The only numbers on the tranny is 3K1033. This tranny is not the original tranny for this amp.
This amp is loud, bright in a good way, touch sensitive and dynamic.
I wish my guitar playing skills were a match for this amp!