Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Jacob on March 06, 2021, 09:26:33 am
-
Hello All!
I’m planning to gut a Super Champ X2 Head, and build Rob’s RR763 inside. Going for something like the Milkman “Dairy Air”
I want to make the Amp as simple as possible, so I’m definitely going to eliminate the Bright Switch, Bright Cap and Standby Switch, as Rob suggests. Also going to make it single Input/Output.
I would love any input on other ways to further simplify this build.
For example: I’m considering omitting the MID control.
Is that as simple as just leaving out that Pot and attached parts?
Or would I need to adjust the values of other components also?
Maybe even reduce it to a single “Tone” 5F2a style?
Also thinking about Cathode Biasing? I thought I had seen this mod for the AB763 on Rob’s site somewhere, but can’t find it for the life of me now ¯\_(ツ)_/¯
I’m not concerned about the final result sounding exactly like an existing/original AB763. Just wanting a Simple, Robust, Cleanish, Fenderish thing to pair with my AC15 “lite” that I built in a similar way.
(And I’m good with modding the Chassis as needed.)
Anyway! Any guidance or advice would be greatly appreciated.
Thanks!
Jake
(Tried to include a photo of the layout in the post, but don't know how. I think it's attached below?)
-
Take a look at this schematic by Sluckey:
http://sluckeyamps.com/misc/AB_Lite_II.pdf
I think it checks your boxes, though I am not familiar with the chassis you have chosen. This is a very nice amp, and I use it to pair up with a BJ in a stereo rig.
-
For example: I’m considering omitting the MID control.
Just replace the mid pot with a 6.8K resistor. My preference would be to just use a 250K-A pot for the mid pot. That way you still have the mid control up to about 5, but beyond that the pot acts to lift the tone stack for a raw sound. Worthwhile IMO.
Also thinking about Cathode Biasing?
Easy to do. Just remove the bias supply and copy the Deluxe 5E3 output circuit. Keep the screen grid resistors.
https://el34world.com/charts/Schematics/files/Fender/Fender_deluxe_5e3_schem.pdf