Simmons SDS-3 Voice

Since this module is finally working (thanks to THeff for the great job he did debugging) here’s a pcb layout for a 1u MOTM module.

I have use SMT technology to be able to cram everything on the board. The good aspect of it is that there’s not much wiring to do, just 5 cables going to the jacks.

I’ve replaced the CA3080 with a LM13700 SMD on Rev C boards.

Power consumption: 21 mA +15, 12 mA -15

I have made a small run of pcbs to sell, 15€ + Shipping : 4€ Europe / 8€ Rest of the World 

(PCBs are red solder mask /  HASL plated)

Schematic :

Bill of Materials :

Mouser Shopping cart (pots & switches not included)

Pots and switches available at Small Bear Electronics

Stencil :

Frontpanel :

Simmons SDS-3 Frontpanel

Simmons SDS-3 Calibration Notes :

First, set all pots counterclockwise except Decay that should be set to 10.

Toggle the LFO switch to the off position and the BEND switch to the “fall” position.

Connect a scope to the output jack.

Connect a fast trigger to the Trigger input. This can be a square wave from a VCO or an LFO. Adjust the frequency till the module produces a continuous tone.

Adjust the PITCH pot till you get a 1 kHz sine wave.

Start adjusting the OFFSET trimmer until the sine wave is centered around 0 V.

Turn the NULL trimmer to perfect the sine wave shape. It will tilt towards left or right, adjust till it’s balanced. Listening to the output will help you find the sweet spot.

Finish by adjusting the GAIN trimmer to obtain +/- 5v peak to peak at the output.

That’s it!

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