Well, unfortunately the 100s did not feature a line out from the preamp stage(this was a feature that appeared on amp only in the mid-'70s, and your amp, even if it were one of the later models with reverb and tremelo, is no newer than 1970). You would need a line out(this is where the guitar signal gets branched off after the tone controls and rev/trem but before the power amp section)to drive a separate amp. The Coliseum you are probably referring to is the Coliseum Slave amp, which is just a power amp. These were "added on" to a rig to power additional speakers, taking the signal from the line out of a regular(with tone controls, preamp, etc) Coliseum head. All of the Coliseum amps were transistor, while your 100s is tube, of course, a much different sound. Are you using this for bass or guitar? You could conceivibly have a mod done to add a preamp out, BUT BUT BUT it would be in your best interest to leave the amp stock...my amp tech told me it's a real pain in the ass to do, and it would ruin the vintage factor/value. How much more power do you need? It shouldn't be that hard finding another 60 watt Sunn head to add to the stack. Even though there are a variety of model names/numbers, they're all essentially the same amp(60w, 2x6550 or KT88 power tubes; volume, bass, treble, contour+boost switch controls, 24" wide, rev/trem on '68 models and later). Please describe your set-up, and what you want to do to expand it.
