Hi. I'm in search for a twin reverb amp and I'd like to know about the differences between the different versions of the amplifier. As far as my knowledge goes, the first version is the blackface, 85w, from 1963 to 67. Then, after the cbs takeover, from 1968 to 1972, they were silverfaces without master pots and 100w of power (or 85???). From 73 to 75, they added a master vol put, but how did this simple addition altered the identity of the twin reverb. Many people say that because of the master volume pot the tone was degraded. From 76, it was the ultralinear region and the power was up to 135 w,but the tone got worse. I am mainly interested in the silverface models, because of my low budget, and of course before the ultralinear. What is the difference between the non master volume silverface and the master volume one? Can I just solder some wires and bypass the pot, and do some mods to convert it to blackface?