Which Dumble to build?

[MarkB]

I have a Bassman head that I'd like to use for a Dumble build. With the different schematics it difficult to know where to start. Any suggestions for a basic Dumble build that get's the classic sound, but without all the bells and whistles?

[Bob-I]

I have a Bassman head that I'd like to use for a Dumble build. With the different schematics it difficult to know where to start. Any suggestions for a basic Dumble build that get's the classic sound, but without all the bells and whistles?

Start with the Hybrid-A. Great sound with enough bells to make it interseting but not overwhelming.

[Normster]

Yup, Hybrid-A, then tweak to taste.

Here are some pics of the two conversions that I did.

http://bad-domain/LorensSFBM/LorensBassman.htm
http://bad-domain/NormsSFBM/Mutant%20Bassman.htm

The Bassman is actually a really easy amp to convert. Note that both of these use the extra tube for reverb. In retrospect, I wish I had used the tube for a Dumblator.

[MarkB]

Where did you get those knobs? There's no room for normal knobs in the input jack holes.

[Normster]

Those are EDP knobs (p/n 45KN024) from Mouser. They're .93" diameter but I elongated Normal channel #1 input jack hole to make room. You pretty much have to do that anyway to use 24mm pots. As an alternative, you can use 16mm pots and smaller knobs. (That's what Andy Fuchs does when he mods a Bassman.)

[tonelab2]

Wow! Very neat, clean work. What push/pull pots do you use? where do you get them?

[Normster]

Wow! Very neat, clean work. What push/pull pots do you use? where do you get them?

Thanks. Those are just Alpha pots (313-1601-100k, 250k, 500k) from Mouser. They only have them in linear taper so you may need to use the 100k for a mid pot.

[MarkB]

AES has 250K and 500K audio pots.

[Icetech]

Norm.. what is the deal with a dumblator? i thought its just a line in/line out.. but guys seem to be talking like its the holy grail now?

[Normster]

I guess it depends on whose tone you're trying to cop.

My reason for wanting a Dumblator is a bit more practical. I've found that I prefer digital reverb over spring reverb for OD tone. I have a nice rack effects unit that only works in a powered (buffered) parallel loop. It just doesn't respond to a passive serial loop for some reason.

[dobbhill]

Many effects units require a low impedance source to drive the input, as they have a low imp. input~10k or so. A simple unbuffered line out is severely loaded down by that, which affects tone in a very negative fashion. The recovery stage of the Dumbleator is not as critical but can allow you to use pedal level effects after the preamp.
HTH, D