Work on the Hammond T-422

Some nice weather today so I did some work on the Hammond.  This beast is way to heavy to carry around and I don't really have room for it in my house so my current plan is to modularize all of the individual components.  These are some shots of the built in Leslie unit.  The cylinder is made of what appears to be a polystyrene or related polymer although it seems a bit tougher than styrofoam.  Looks like a two motor system.

Is that about a 5" speaker?  Maybe that could be upgraded.  Thinking about a using a stepper motor for this but I might not be able to get enough torque.  Either that or build a preamp and power supply for this and mount it in a separate cabinet.

Started cleaning all the gunk off this board and discovered it is the drum module.  This was still working during my initial test.  Found a piece of wire or solder underneath this board which may have resulted in some shorting.  Needs more cleaning.  I was originally thinking of trying to rig this up to a techno style drum machine.  Maybe I can convert those trim pots to knobs.  I may have to reflow the solder on a couple points.

Reverb tank looks intact and has standard connectors.  I think I will try it out with my Blues Jr.

NAND Mini Modular

Making progress on the NAND mini modular synth.

VSF Video Demos

Here are a couple demonstrations of my new filter design the VSF.



Got the transistors working now.  Changed the resistors to 10k and switched to 3904s.

VSF

Finished building the VSF (described below) last night.  I had to disable the transistors since they seemed to be on continuously.  Very nice distorted complex tone colors out of this thing.  I need to change the pots to 100k from current 1M for VCF and 500k for Q.  The Mura I need to change from 100k to 1M.  Go figure. I will try to get an example of the sound up here soon.  I may try to change the transistors so I can get some control voltage response.

Mura Filter

From the Japanese term for the waste of uneveness this filter will create an uneven distortion of the resonance structure both from the transistor and from the diode in the feedback path.  Connections are described in the picture.  Values can be changed somewhat to match standard values.  RS is a rail splitter.  Saving the other side for an LFO to modulate the Fco.  Have not built this yet but it looks pretty cool in the simulator.

Falstad circuit simulator code:


$ 1 5.0E-6 0.9891409633455756 50 5.0 50
r 336 320 272 320 0 4700000.0
c 336 224 336 192 0 1.0E-9 0.00268564673175871
c 432 224 432 192 0 1.0E-9 -1.876367065692067
r 272 320 272 368 0 47000.0
c 272 320 224 320 0 1.0000000000000001E-7 -2.4144869775373956
174 336 192 432 176 0 100000.0 0.9059 Q 100k
a 336 336 432 336 0 15.0 -15.0 1000000.0
w 336 224 336 240 0
w 336 288 336 320 0
w 432 224 432 240 0
w 432 288 432 336 0
g 336 352 336 368 0
g 272 368 272 384 0
O 432 336 432 368 0
174 336 192 240 176 0 100000.0 0.9257000000000001 Fco 100k
g 240 192 240 208 0
w 288 176 336 192 0
R 224 320 192 320 0 2 100.0 5.0 0.0 0.0 0.5
r 336 288 384 288 0 2000000.0
r 384 288 432 288 0 2000000.0
g 384 240 384 224 0
c 384 288 384 240 0 1.0E-11 -0.939194425306891
w 384 176 336 192 0
w 432 240 432 288 0
w 336 240 336 288 0
w 336 160 336 192 0
w 448 288 432 288 0
174 336 160 432 160 0 1000000.0 0.005 Resistance
d 464 160 464 192 1 0.805904783
w 384 144 336 160 0
w 432 160 464 160 0
w 464 192 464 288 0
w 464 288 448 288 0
t 288 128 288 160 0 1 0.45948822583066745 0.4568213771495246 100.0
w 272 160 240 160 0
w 240 160 240 192 0
w 304 160 336 192 0
R 288 96 288 64 0 1 40.0 3.0 2.0 0.0 0.5
174 288 96 304 128 0 1000000.0 0.10400000000000001 Resistance
w 304 112 288 96 0
o 13 4 0 34 20.0 9.765625E-5 0 -1

Note the resonance wave form has a slight sawtooth edge as well as only oscillating on the positive cycle of the square wave.