Solid State Percussion Synthesizer


The Peasant is currently designing and building a solid state percussion synthesizer. This project is partly based on designs from the good people at PAIA and Midwest Analog Projects, as well as a few others.

Electronics Case

The electronics for the synthesizer will be housed in a nice old wooden box. In this picture the control panels have been fitted and are ready for drilling.

This instrument will consist of a snare drum, a bass drum, 3 tom-toms, a hi-hat, two cymbals, and a woodblock/cowbell. The bottom section of the case will hold the snare, bass, toms, and a mixer, while the top section will hold the hi-hat, cymbals, block/bell, with the external connections along the top edge.

Lower Panel Construction

This is the lower control panel design. Thanks to Tim Parkhurst for the graphic design assistance.

The lower panel is shown with mounting holes drilled and the pcb supports installed, ready for painting.

This project will require almost 300 knobs, so even using inexpensive types would add up to a significant sum of money. After exploring possible options, including making my own knobs, I came up with the idea of using beads from beaded car seat covers, drilled out to 1/4 inch, with a plastic cap on top. There just happened to be a bag of these beads saved in the basement (packrat!), so I made up a few to try.

I liked the result, so 300 plastic caps (Spae-naur 245-106) were ordered, at pennies apiece. Round dots were applied with a paint stick to the first 150, and they were installed on newly drilled and installed bead-knobs. The holes were sized so that the knobs are a tight fit, so setscrews are not required. I did end up using some crazy glue "gel" to secure the knobs to the shafts, and some silicone to hold the caps on to the knobs.

The Panel has been painted with lettering and pinstripes applied. The lettering is Brother p-touch labels and the pinstriping is regular automotive type.

Somebody has some wiring to do!

Snares and Impact Schematic

The first section being designed is the snare drum. Here is the triggering and volume circuitry, as well as the "snares" and "impact" sound generators. These same circuits will be used for the bass drum and tom-toms, excluding the "snares" generator (separated on the diagram with a dashed line).

SCHEMATIC

BLOCK DIAGRAM

Skin and Shell Schematic

Next are the "skin" and "shell" sound generators. Again these will also be used for the bass and tom-toms.

SCHEMATIC

BLOCK DIAGRAM

PC Board Patterns

Here are the circuit board etching patterns, including a component location guide.

SNARE PCB

TOM/BASS PCB

PARTS PLACEMENT

Here is the first prototype pcb for one Tom Tom or Bass Drum, about 80% populated.

The snare, tom tom, and bass drum boards have been completed and installed on the front panel.

The circuit boards can be folded out for access to the components and wiring.

A close-up of the snare pcb and it's wiring.

Mixer & Reverb Section

The mixer board has been completed and is ready to wire up. The pan trim pots for each channel are located on a small daughter board attached to the mixer board.

Here is the mixer schematic, including BBD based reverb.

SCHEMATIC

Here is the pcb pattern and component placement diagram.

PCB PATTERN

PARTS PLACEMENT

The mixer board all wired in place.

Finally, the first panel has been completed!

Power Supply

Next to be built is the power supply. Again, a wooden box was used to house the electronics, in this case a linear power supply module.

This is the power supply diagram for the entire unit.

SCHEMATIC

Drum Trigger Pad Construction

The actual drum pads use piezo discs for sensing. For the snare and tom toms some old obsolete network routers were removed from their metal cases, and replaced by 2 layers of foam rubber with the piezo disc sandwiched in between. This method of isolating the piezo disc in foam within a metal box cuts down on the sensitivity of the piezo, to minimise crosstalk between pads. The metal cases were then attached to a wooden stand, with more foam in between to cushion the pads and further minimise crosstalk. Thick mouse pad rubber was attached to the top surface for a realistic feel and to dampen striking noise.

Room has been left on the wooden stand for the hi-hat, cymbal, and block/bell pads.

A close-up of one of the pads. The foam inside and underneath each pad does a great job of isolating them from each other, as I could get no crosstalk between pads no matter how hard I hit them!

Bass Drum Trigger Pad

The bass drum trigger uses a standard drum pedal in order to retain the "feel" of this type of pedal. A small frame with a metal case was constructed to fit the pedal and house the piezo sensor disc. Again, the metal case is lined with foam, cushioning the piezo disc inside.

A picture of the actual trigger pad assembly, including the pedal.

Here is the system so far, with everything finished except the pads and front panel for the cymbals, hi-hat, and block/bell section.

Sound files!

A sample of a basic drum kit, showing the dynamic range of the sounds

ssdrum1.mp3 (220K)

A bit of playing using the same settings.

ssdrum2.mp3 (118K)

The sounds are certainly not limited to "normal" percussion!

ssdrum3.mp3 (241K)

Here is a sample of some of what the bass drum can do.

ssdrum4.mp3 (650K)

And a sample of the range of sounds that the SN76477 based snares section alone can do.

ssdrum5.mp3 (685K)

Stay tuned for more updates!