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Project Notes

#477 Rakit Drum Synth

Building the Rakit Drum Synth kit - a very nicely produced clone of the classic Boss PC-2/AMDEK PCK-100 percussion synthesizer.

Build

Notes

I just had some fun building the Rakit Drum Synth kit. It’s a very well produced kit that recreates the classic Boss PC-2/AMDEK PCK-100 percussion synthesizer, staying very true to the original design and components.

Here’s the demo from Rakit:

clip

Circuit Design

The Rakit Drum Synth is based on the classic Boss PC-2/AMDEK PCK-100 percussion synthesizer, with mods:

  • Attack on/off
  • VCO & LFO wave shape selection
  • Pitch CV input

In layout and parts selection it is very close to this old AMDEK PCK-100 schematic:

amdek_pck-100_schematic

The design uses a number of legendary parts that are interesting in themselves including the: the JRC4558 JFET opamp, and Rohm BA6110 voltage controlled op-amp in an unusual SIP-9 package. These parts are common in many famous products from guitar pedals to synths. Whether these parts are “key” to the sound is a matter of great debate;-)

I discovered interesting attempts to recreate the (now largely unobtainium) BA6110, including this PCB design on OSHPark.

Parts

Component Qty Checked & Installed
3.5mm Mono Socket 3
A100k Log Potentiometer 4
B504 500k Linear Potentiometer 1
B102 1k0 Linear Potentiometer 1
50k Trim potentiometer 2
2.1mm/5.5mm Barrel Power Socket 1
Right Angle SPST Slide Switch 2
Horizontal DPDT Slide Switch 3
1n0 Box Capacitor 4
3n3 Box Capacitor 1
22n Box Capacitor 1
47n Box Capacitor 3
390R 0.6W 1% Resistor 1
1k0 0.6W 1% Resistor 5
4k7 0.6W 1% Resistor 4
10k 0.6W 1% Resistor 5
22k 0.6W 1% Resistor 4
33k 0.6W 1% Resistor 2
47k 0.6W 1% Resistor 12
56k 0.6W 1% Resistor 1
100k 0.6W 1% Resistor 11
220k 0.6W 1% Resistor 2
1M0 0.6W 1% Resistor 1
4M7 0.6W 1% Resistor 1
OTA IC BA6110 1
Op Amp 4558 IC 1
Op Amp 358/2904 IC 3
3mm Blue LED 2
Signal Diode 1N4148 3
Schottky diode IN5819 1
2N3904 NPN Transistor 2
2N3906 PNP Transistor 2
2SC945P NPN Transistor 2
1u0 Electrolytic Capacitor 3
10u Electrolytic Capacitor 2
100u Electrolytic Capacitor 1
PCB – Top, Inside, Left Wing, Right Wing 4
Battery Snap to Barrel 1
Rubber Tube 4

kit_parts

Construction

Rakit have a very clear assembly guide online. Recommended build sequence:

  • IC’s
  • transistors
  • diodes
  • electrolytic capacitors
  • LEDs
  • resistors (all vertically mounted)
  • Trimmers
  • box capacitors (not polarised)
  • slide switches
  • 3.5mm mono sockets
  • piezo disc wires
  • potentiometers and switches
  • rubber feet

My only embellishment on the procedure was to go for Boldport-style solder domes with my favourite 2% Ag solder;-)

Fitting the all the semi-conductors and electrolytic capacitors..

build_step_1

With remaining caps,resistors, slide switches and sockets..

build_step_2

Attaching the piezo pad:

build_step_3a

And seating the pots and top-panel switches..

build_step_3b

All finished! Rear view..

build_step_4a

And from the top..

build_step_4c

Here’s a quick demo.. just mucking around trying to discover the range of sounds it can produce:

clip

Credits and References

About LEAP#477 AudioDrumSynthMusic
Project Source on GitHub Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is my personal collection of electronics projects, usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting (IMHO!).

The projects are usually inspired by things found wild on the net, or ideas from the sources such as:

Feel free to borrow liberally, and if you spot any issues do let me know. See the individual projects for credits where due. There are even now a few projects contributed by others - send your own over in a pull request if you would also like to add to this collection.