This is my 1976 Bassman 100. It is a 100 watt amp, and you would think it would simply be a larger version of the 50 watt Bassman tops of the 60's and 70's. That's not the case, however. The 50 watt tops had an extra tube mixing stage between the preamp and the power amp, and the 100 does not. It's really a simple amp. The power transformer looks to be the same as used in the 100 watt Twin Reverb, but the output transformer is noticably bigger.
Shunning the 70's Fender circuitry, I rebuilt the amp to resemble the AB763 Fender Blackface circuit. The amp now is basically a Super Reverb pre in one channel, and a Twin/Showman in the other, but both without any reverb or tremolo. I removed the crappy master volume, and tried to implement a Presence control but couldn't get it to work. I saw a post on Ampage about a mod that adds a "Resonance control" which essentially is a variable negative feedback control, and added that instead. I have to play it some but it seems pretty cool in that on one end of the pot you get a lot of distortion and crunch and on the other end you get uber clean and spank.
Since the mods this thing is a rock machine!! Great cleans, and great overdrive. It sounds great through my 4x12. I put some NOS preamp tubes in it, and tried out the long bottle TAD 6L6 power tubes, they sound great. Click on the pics below to see the changes I made.
As you can see, the cab and faceplate have seen better days. It looks like the amp was dropped or rammed into something at some point. The cab was cracked open on one end and I took it to my friend Danny for repair. The chassis was bent in and I had to buy some pressure clamps to straighten it out. Both transformers were loose, and the output transformer was bent towards the cracked side. I had to undo the bolts holding it in and bend the tabs straight again. I bought new tolex and hardware and am in the process of recovering the cabinet.
