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Two Preamps in a B3


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The following comment and photograph were posted Aug 14th in the "Winwood new Gimme Some Lovin..." thread.


Can someone please explain why there were two tube amps in this Hammond?




I was curious about this too. In a recent unrelated email conversation with Bob Heil (Heil Sound), he disclosed that he has played Hammonds since he was twelve and played theater organ professionally. He also extensively modified B3s, including the installation of two preamps.


sayeth Dr. Heil:

The B3 was special. I split the matching transformer and added another B3 pre amp and swell pedal Maas Rowe string bass (never did like the 'thud' bass). This presented an actual two channel Hammond - lower manual on the Left Leslie, mid manual on the Right Leslie and the top manual was a Kinsman home organ through a JBL system.


The dual preamp B3 is in other Traffic videos. There's a '71 video in which he plays a C3 that appears to be so modified.


Edit: Organ Forum thread about Steve Winwood's Custom B3 and C3

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Hello Mr. Bradley. How thoughtful to bring this up :)


My initial guess had always been a way of having output signals for each manual.... but never understood why it couldn't be done within a single preamp.


I also thought there was a spring reverb in there too.




Hurray for resolving the mystery

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I always thought both manuals going out through the same output and leslie was muddy at times.


The two manuals share the same tonewheels, so it would be impossible to separate the outputs. It would be like trying to separate broth from water once you mixed them. Some digital clonewheels model two identical sets of tonewheels with each pair phase-locked, so they can get away with it. It would be impossible to do so physically. Part of the character of a tonewheel organ is that all the wheels are spinning out of phase. However, tonewheels are shared between many notes. If you play the same note on both manuals, it's sharing the same tone wheels (it just boosts amplitude to accommodate for the second voice) so there is no phasing issues to even occur. This is a huge part of the tonewheel sound. If there were 9 individual tonewheels for every note, the phasing would be absolutely nuts.


The only way this can be done is to create two completely identical sets of tonewheels, phase-locked, that respond identically, just have different outputs. This is physically impossible in the real world, but it's dead stupid simple in software.

Puck Funk! :)


Equipment: Laptop running lots of nerdy software, some keyboards, noise makersâ¦yada yada yadaâ¦maybe a cat?

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While it"s true there is only one set of tone wheels they supply 2 independent sets of buss bars . Each set of bus bars is controlled/gated with a unique set of drawbars and of course the upper or lower manuals. The tonewheel signals riding on the 2 sets of bus bars are connected to individual matching transformers whose outputs are recombined through the vibrato switch terminals and routed to the terminals of the preamp.


But it would be easy to break in at this point and maintain the split bus bar sets such that the upper goes to one preamp and the lower to a separate preamp.


Sparing further attempted explanation I"m guessing that with 2 preamps only the upper manual has vibrato control.

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