What Does This Mod Do?

[Big Dan]

Been looking at doing something to my SF Showman after I BF it, and someone mentioned this:

http://www.schematicheaven.com/dumbleamps/mod2.pdf

Looks easy enough, but I am unclear as to exactely what is will do? It is listed in the "Dumble" section of Shematic Heaven.

Ok, I get a "Rock/Jazz" switch and a boost switch, but is the gain structure all that changed?

Thanks,
Dan

[Big Dan]

Bump?

[SeanF]

it does a lot. The "rock" setting really does make it more of a rock machine (especially at full volume), but the cleans won't be classic Fender BF any more. They're still good, just not the same. The "jazz" setting is exactly what it says. I'd give it a shot, you can always change it back. I used it once on a Bandmaster Reverb and left it that way; did it on a Twin and changed it back.

[Big Dan]

it does a lot. The "rock" setting really does make it more of a rock machine (especially at full volume), but the cleans won't be classic Fender BF any more. They're still good, just not the same. The "jazz" setting is exactly what it says. I'd give it a shot, you can always change it back. I used it once on a Bandmaster Reverb and left it that way; did it on a Twin and changed it back.

Thanks Sean. It sounds pretty cool to me. I figured the reverb/trem channel will still retain the BF sound, so I want something different for the clean channel. I guess I will do it! Thanks for the input!

Dan

[bob-i]

That is a 70's Dumble preamp. You'll get much more mids and a generally more balanced overall tone in the rock position. The jazz position cuts bottom and top and gives a soft, gentle tone (not my cup of tea). The boost is very cool, it disables the tone controls which adds tons of gain and overdrive.

Personally I like this mod a lot. I've built several Dumble style amps and where I prefer the 90's Dumble, that requires much more evasive mods to an amp like this. You really need an overdrive section for the 90's version where this 70's version has a nice grit and grind just like this, if you're gonna crank it up of course.