Can I convert the powered speaker out on an old amp to a line out? I have heard this can be done with a resistance load, but I am hesitant to try without guidance or feedback. I found an all tube, military PA amplifier from the 50s. I tried running it for a bit, and it gave some very cool tone. With a preamp over-driving it, it delivered phenomenal low end fuzz. It definitely doesn't have the amount of power I need for my setup, and it lacks a lot of features I use. I am wondering if it is possible to use it as an effect in my effects loop without damaging it (or my amp) from the lack of resistance load. I have heard I can set up a resistor in parallel with the output to prevent damage to the amps, but how large of a resistor should I use?