Anyone here have any experience in the tonal differences between Marshall and Fender output transformers? I know there's a primary impedance difference between the two makes. I was thinking about changing the stock OT in my '73 40 watt Bandmaster Reverb, which is smaller than my Fender Blackface Bassman 40 watt OT, to something a bit beefier. I was even considering throwing in one of the JCM800 50W Drake OT's I have on hand. The Drake OT would also give me the switchable impedance options. Now I would still like to run 6L6's in the amp if I installed the Drake OT. Then there's the slight difference in OT primary impedance between the two (Fender has 4.2K and Marshall/Drake I am figuring is about 3.4K). The Drake OT is actually huge in size compared to the stock Bandmaster Reverb OT. The Bassman OT is somewhere in between the two. So is it correct to ASSume that the Drake OT would provide my Fender with a bolder bottom end punch as well as more clean headroom? I know that swapping in a Blackface Bassman OT would do this somewhat. I was even considering looking for a Twin Reverb OT and running my Bandmaster at 8 ohms (two 6L6's). I want to retain the Fender character somewhat as well, so that is why I am wondering what a Drake/JCM800 OT would do tonally to a Fender? Would the OT with a slightly lower primary impedance of 3.4K give off a bit more punch and volume than the higher 4.2K impedance as well? I would really appreciate some good insight on this subject from anyone that is willing to explain it with some good theory.