I just got this monster, a Fender Dual Showman red knob in pretty good cond. I know some people don't like this amp. but f... is dam loud and the clean is wooow (is a dream) and the od is a charm too. this amp is good for country music to blues music. I hear we can blend the channel? what is mean by blend the channel, does it like the marshall jtm 45 we can use jumper cable?
here a pic

I believe you just use the second set of inputs if you'd like to blend the channels. In the early 80's I had a Sidekick Reverb 65 (SS) and it had the same feature. I'm not positive, but I think the design is from when Rivera was with Fender.

thanks for the info

It's true; I had a "red-knob" The Twin in the late '80s and early '90s.

If you stick the effects-loop level-switch in-between settings, it will give you a boost, as well. Perfectly safe- recommended by no less than Bruce Zinky (designer of the Fender Vibro King and Tone Master, among others).

I hear conflicting accounts of the "red-knob" Fender amps, concerning sound & quality, but I have noticed that they tend to be priced pretty low, when I see them offered. Any model I should keep an eye out for? I'm not a tube purist, by any means, so that's not a deal-breaker, for me.

for me I think is just some people they don't like fender amp
I know this one is not one of the best one but is usa made.
this amp is 25 years and I just look inside and everything are original and even the tube are original. all the pot have no noise when I use it. now I will need to change all the tube inside to get a better quality sound. right now the sound is ok but I will replace with brand new tube.