Tuesday, November 24, 2015

How to Dumble MOD a Fender Black Face

Alexander "Howard" Dumble has revolutionized the world. He started out in California with a small amp shop where he specialized in modding Fender amps.  One of his most popular mods is the Ultra Phoix mod.  In my search for the illusive Schematic and secret information surrounding the mod, I came across this article "Cool Mod for the Normal Channel"   You can read up on it at the following link.  Cool Mod for the normal channel

As I am not a amp builder, (but someday hope to be) I recruited my friend John Dandry to assist me.  He is an amazing amp builder located in New Orleans. We used my 1964 Fender Princeton as the donor amp.  We used Push Pull switches instead of the regular switches in case we did not like the results. This mod is truly amazing. I have never heard a Fender Princeton sound so good.

This is the work that was done.

1. Replaced: 2x 100k plate resistors in preamp and  all Electrolytic caps in amp.
2. Removed fixed 27k bias resistor with 10k pot and 22k resistor for adj. bias
3. Added Shielded cable at input to lower noise.
4. Mods: Cool Mod : Rock/Jazz and boost pull knobs on treble and bass.
5. Rock/ Jazz - tone filter Boost - tone stack bypass Local feedback on gain stage Mid control
Thank you to the following:
1. I want to thank Dumble for his creativity and intuition 
2. I want to thank Steve Aloha for writing such an amazing document on the Cool Mod.
3. I want to thank my friend John Dandry for his amazing skill and workmanship.
     (Click here for John Dandry Contact Information)

Here is a Video of the final result before putting the chassis back into the Cabinet.  This is only the amp with no effects.
After Dumble Cool Mods 

Here are some pictures of the inside of the Chassis