I use a low powered (20 watts or so) vintage class A amp for the bulk of my playing and have been trying to make it "bigger" by slaving it out to a seperate power amp and speaker. I tapped the speaker output on the amp with a 3k resistor and a 300 ohm resistor to ground. The signal was still pretty hot compared to preamp level so I added a pot to the circuit, a 50k A&B I had laying around. No doubt it's not the ideal value or taper, but it does the job and the signal level is fine now. I had a cab built to the same specs as the original amp, and installed the same speaker that I use for these amps, a 50 watt Weber ceramic Blue Dog. The cab is powered by a 2-6L6 cathode biased power amp from a late 50s Baldwin organ. It sounds similar to the original, but the tone is harder and brighter, not as warm as the original. I tried the slave output to the power amp of a 100 watt head, in case it was the organ amp that was affecting the tone (I considered this unlikely, as the amp is pretty hi-fi) with the same result. To complicate matters I had Wobo build me a double looper with remote foot switches, and the slaved output is so bright and gainy going into the looper that it squeals when I turn the treble up near the normal setting I use, and the input is distorted even when I pull the slave output down way below where I generally need to set it. I don't have this issue plugging the slaved output direcyly into either power amp. I know next to nothing about electronics, but my impression is that there is a severe impedance mismatch with the loopers input, but I'm wondering where the loss of fidelity occurs even going directly into a power amp. Do I need a better circuit design for the slave? It doesn't matter if the original amp is connected to a speaker or a dummy load. I know other people have slaved smaller amps into big power amps. Do they settle for a close facsimile of the original tone, or is there a better circuit for reducing the signal from the OT and making a more compatible interface with power amps (or especially this looper)?