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Dumblefy? What's that about

10/13/1999 3:58 PM
Dumblefy? What's that about
I have just become aware of the mystique and rarity  
of Dumble amps...the photos of the epoxy covered boards  
were amusing and provoked questions in my mind about  
how repairs would be accomplished...but anyway:  
What does it mean to Dumblefy a preamp section? What are the tricks here?
10/13/1999 5:54 PM
Don Symes

Add a post-EQ overdrive section with a post-OD EQ section of its own.  
There are some opinions and a few schematics floating around.
10/14/1999 3:01 AM
Steve A.
Re: New drawings uploaded!
    Glad you asked because I just uploaded the latest version of "Dumble Mods for the Normal Channel" which includes layout drawings for 3 different versions: basic, with the Rock/Jazz switch, and with the Rock/Jazz and Boost switches:  
Steve Ahola  
P.S. In case the title isn't clear, the drawings show how to convert the Normal channel preamp of a BF/SF XXX Reverb amp over to Dumble specs and H.A.D.'s rather unique tone stack.
10/14/1999 5:34 AM

Wow! Thanks a bunch, Steve, great work. Even *I* can understand what's going on in it.  
10/14/1999 7:36 AM
Ted Matsumura

What is the optimal BF/SF fender to start these mods with? I would presume something with like more than a single tone control, preferably mid treble and bass? So bassman, twin or pro? with reverb, or external reverb ok?  
If I found a cheap SF Bassman head on ebay, could anyone make these mods for me? How much time and cost would be involved?
10/14/1999 8:34 AM
Steve A.

    For a SF Bassman head you could "Dumble-fy" the Deep Channel. I recommend adding in the Mid control, which could be done by taking out the #2 input jack and putting the Volume control there. With that setup you'd have the regular BF Fender preamp on the Normal channel and the Dumblized preamp on the Deep channel.  
    But for my own SF Bassman head that finally arrived today, I have much more devious plans... a complete Dumble Overdrive Special clone with footswitchable relays for channel switching and the preamp boost.  
Steve Ahola  
P.S. I thought I better clarify once again that the "Dumble Mod for the Normal Channel" uses only the first two stages of the 1977 D-ODS design for the Dumble Clean channel. As for finding someone to do these mods for you, why not give them a try yourself first?
10/14/1999 1:30 PM
MJ Harnish

Now you're talking Steve. I've been doing the same with my previously hacked bandmaster chassis (which is basically the same thing as a bassman except for the tiny OT which I've already replaced). The chassis work really well; when you dump the 2nd set of inputs (the trem channel in the bandmaster),you gain the additional hole needed for the bass pot (Input 1 is spaced the same as the pot controls).  
I ended up with Volume, Treble, Middle, and Bass, followed by the Jazz/Rock switch and then the rest of the controls (OD and Power amp). Once the faceplate is made you won't be able to even tell that there are additional holes drilled in the front panel.  
There's also a LOT of extra space in the chassis; I built my board with fairly decent spacing and I still have at least 4" of empty space between the board and where the PT mounts.  
Eventually I'll have pictures up once things are a bit more presentable...  
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