I was going to leave this alone, but found an error in my calculations when calculating the % of reduction.

2nd resistor is in parrallel with 60K Z of of amp. So to determine % amp sees = 60K " R2/ (R1 + 60K " R2), where R1 top resistor and R2 is bottom in parrallel (")with amp impedance. All good now.

These are corrected:

R1, R,2

33K, 33K, = 60% volume reduction, input Z = 54K

27K, 33K, (top, bottom resistor) = 56% volume reduction, input Z = 48K

22K, 33K, = 50% volume reduction, input Z = 43K

For less reduction:

20K, 60K, = 40%, volume reduction, Z 50K ohms

10K, 60K, = 25%, volume reduction, Z 40K ohms

10K, 100K, = 21% volume reduction, Z 47.5K ohms

The idea of the jumpers is you put the divider between the two interconnects using jumpers to make connections. Make sure everything is working to your liking (volume knob is where you want it) before you start unsoldering and soldering.