PRHunt
I void warranties
Guys, in my opinion, don't mod the deacy amp circuit.
Use something active ahead of it. You need high input impedance (say 1Mohm) in order to not load down guitar pickups, and to not interfere excessively with the guitar tone controls.
A simple buffer would be perfect if you don't want to always use the treble boost or some other pedal. You could perhaps build the buffer into the amp if you want, and maybe make it bypassable.
The resistors at the deacy input set the input impedance, but they are also providing a DC bias on the input (needed, since the amp is running off a single voltage supply). In a conventional input stage, one might see two identical resistors which would set the DC bias point at 1/2 V supply.
In the KAT deacy schematic, R1 and R2 are not the same, so the resulting voltage divider, by my calculation, sets a DC bias of about -1.8V. This would result in asymmetric clipping with larger input signals, and probably contributes to the overall sound. (And there is no point using this amp clean, is there?)
You *may* be able substitute higher ohm resistors in the same ratio, but I have no idea if that would work in the overall design.
I wouldn't mess with R3, unless you know what you are doing, as it is performing a different task.
Anyway, this is just my opinion!
@Steeno, great work sleuthing out the grounds and signal return issues!
Use something active ahead of it. You need high input impedance (say 1Mohm) in order to not load down guitar pickups, and to not interfere excessively with the guitar tone controls.
A simple buffer would be perfect if you don't want to always use the treble boost or some other pedal. You could perhaps build the buffer into the amp if you want, and maybe make it bypassable.
The resistors at the deacy input set the input impedance, but they are also providing a DC bias on the input (needed, since the amp is running off a single voltage supply). In a conventional input stage, one might see two identical resistors which would set the DC bias point at 1/2 V supply.
In the KAT deacy schematic, R1 and R2 are not the same, so the resulting voltage divider, by my calculation, sets a DC bias of about -1.8V. This would result in asymmetric clipping with larger input signals, and probably contributes to the overall sound. (And there is no point using this amp clean, is there?)
You *may* be able substitute higher ohm resistors in the same ratio, but I have no idea if that would work in the overall design.
I wouldn't mess with R3, unless you know what you are doing, as it is performing a different task.
Anyway, this is just my opinion!
@Steeno, great work sleuthing out the grounds and signal return issues!
