Re: how does one use an amp as a pedal?
Do a web search for the Garnet Herzog - basically a hot-rodded Champ used as a distortion box. It's what Randy Bachman used for "American Woman". Terry Kath used a similar setup with a small Bogen PA amp generating the overdrive, and a large Knight or Fender to amplifiy it.
The idea is to use a small amp cranked up to get distortion, then use part of that signal to drive a second amp. The important part is to take the signal off at the output stage of the little amp - the idea is get full-blown output stage overdrive. The output stage is where we get the nice compression and sweet singing distortion.
But the little amp still needs a speaker load - you can't just plug a speaker output into a guitar input. So, the little amp either needs to have its speaker connected, or have an equivalent load resistor.
Then , it needs a line-level output signal. This can be done with a simple resistive voltage divider wired in parallel with the speaker. Some amps have a line out off the output stage. Or, you could use something like the H&K Red BoX, but with it's speaker simulation turned off. Since the big amp is going to have speakers, you don't need a speaker sim on the small amp's output.
