well, ok, maybe 'match' was the wrong term but at the moment the power amp barely even notices it's got a signal going into it! Surely I need to at least bring the impedance up into the kΩ?
The speaker output of the tape machine is going through a little 2 channel passive mixer (just across a 47k pot and then through 47k resistor). The output from this works fine if I plug it into a guitar practice amp, but is barely audible when wired through the amp. which by the way is this one:
M034
Is it really enough to just whack a 10kΩ resistor in line (with the signal i assume)?