So, I'm stumbling around the Internet looking at random guitar sites the other night, and I found the following tip relating to JTM45's: Output Impedance. The standard JTM reissue output transformer has a primary of about 6.5k, which is about 65% higher than your typical two-tube Marshall iron in an EL34 amp (e.g. 50w plexi). If you want more of an aggressive sound, set the selector one notch higher than the load, i.e. set it at 16-ohms for an 8-ohm cabinet, which tends to make the tone much more Marshally. It has been said that using the impedance selector in this manner will make the amp louder and it will sound less "constricted". This sparked my interest because, while I don't have a JTM, I do have an EL34-based Mojotone Tone Machine amp, which also has a primary of 6.6k, like a JTM45, according to Greg Germino (he built the amp). The Tone Machine is currently functioning as a back up to my Demeter. While the Tone Machine has always been a solid, interesting amp, I came to have one issue with its performance - at "band" volume, the sound would get kind of squashed and mushy, especially if any kind of drive pedal were engaged. Hence, it got replaced as No. 1 by the Demeter. I decided to "mismatch" the impedance as suggested by the excerpt above. I connected my 8 ohm cab to the 16 ohm tap on the amp. Lo and behold, the amp sounds much crisper, louder, aggressive, and, indeed, less "constricted" than it does with the "matched' load!!! Drive pedals all of a sudden are useful at high volume. Nice. I hate to use cliches, but it's like a whole new amp. I'm kind of a neophyte on the more technical stuff involved with guitar amps, so I don't know the "why" of all of this. Does the story make any sense? Any observations? Thanks!