Analog Percussion Synthesizer Kit
PCLONE2 is a recreation of the (now rare) PC-2 percussion synthesizer which was made by Boss during the 1980s (and also released in DIY kit form under the Amdek brand name as the PCK-100). The PCLONE2 kit is based on the original schematic (with a couple of changes due to the scarcity of some now obsolete components). The kit includes all the parts necessary for the build; two printed circuit boards, electronic components, potentiometers, knobs, switches, sockets, fitting screws etc. It includes a custom designed, laser-cut, case (made from 3mm acrylic sheet with 5mm acrylic side cheeks) and a laser etched acrylic laminate fascia.
This is a completely analog synthesizer with a single VCO. There is a pitch sweep function, a decay envelope and an LFO with rate, depth and wave shape (triangle/square) control. Unusually for a percussion synth there is no noise source, but you’ll soon realise this isn’t your typical percussion synth! Sounds are triggered by an input pulse (5V-9V works fine) or by tapping on a piezo sensor which is mounted behind a pad on the front panel.
There are three unconnected 3.5mm sockets labelled CV1, CV2, CV3. These, together with a prototyping area on the PCB, are to make the box easily mod-able. I will be documenting some simple mods I have already found (including a pitch CV input using a single resistor), and plan to get a growing list of mods together.
The box has the following controls:
- TRIG LEVEL – Sets the sensitivity of the trigger input. The voice circuit responds differently depending on the intensity of the trigger pulse (this is especially nice when tapping it with a finger). The TRIG LEVEL knob controls this response.
- PITCH – Sets the basic pitch of the oscillator. This works alongside the SWEEP controls.
- DECAY – Controls the decay of the volume envelope (so how long the sound takes to fade out after it is triggered) and also controls the sweep time. Sweep, pitch and decay interact in ways that reward experimentation.
- SWEEP AMOUNT – Each time the sound is triggered, the pitch of the oscillator can be swept up or down by a selectable amount. The circuit has a characteristic sweep where the pitch drops low and rises, or starts high and falls. In the original PC-2 a centre-tap potentiometer was used, so the centre detent turned the sweep off. Since it is difficult to obtain a suitable centre tap potentiometer at a reasonable price, the PCLONE2 uses a separate SWEEP DIR switch to control the sweep direction and the potentiometer just controls the sweep range – the end result is the same and this configuration actually gives a little more flexibility than the single control of the original
- MOD RATE and MOD DEPTH – The PCLONE2 has a Low Frequency Oscillator (LFO) which modulates the pitch. The wave form is selectable as a Triangle or a Square wave via the MOD WAVE switch. The LFO is key to getting some of the wackier bleepy-bloopy dub siren noises this thing can make – at the top end of the LFO rate, some FM or PWM-like sounds are possible.
- The CLICK switch enables the “attack sound” circuit that makes a click each time the sound is triggered. The PCK100 manual described this as the “realistic sound of a stick striking a skin”. I am not so sure I quite agree with that but being able to switch this circuit in and out does open up a bit more sound variation (The original did not have this switch). The effect is often quite subtle.
- The VCO WAVE switch allows the voice oscillator to be switched between a mellow triangle wave and a harsher square wave (The original did not have this switch, although it was a common mod to add it)
NOTE: This kit is a recreation of the PC-2/PCK100 based on the original schematics. I needed to make a couple of modifications on account of the rarity of the Roland BA662 op-amp which was used in the original. This version uses the BA6110 op-amp with a current buffer circuit to more closely match the characteristics of the BA662
The PC-2/PCK-100 boxes were released by Roland as percussion synthesizers. Make sure you know what to expect.. you’ll get excellent bleeps, bloops and spacey dub siren sounds but this is NOT a drum machine or something you can play synth bass lines or funky lead solos on!