The Business Card Synthesizer is a tiny synth that can be connected to a Business Card Sequencer, other synth gear, or played by itself.

These fun little kits were introduced at Knobcon 2018 as a build workshop. Now you can get your very own.

Headphones can be connected directly to the output of the synth, and there are plenty of knobs to play with, so you can easily make noises anywhere. Great for learning about synthesizers!

We send you a board and a bag of parts so you can build it yourself. Difficulty level = medium (it’s all through-hole, but some of the soldering is kind of small). The kit includes the PCB, preprogrammed microcontroller and all required parts to build kit.

Features:

• Pulse, square, triangle, and sawtooth waves
• Glide
• 2 LFOs with pulse, square, saw, triangle and ramp shapes
• Attack / Decay
• Low-pass filter
• Sample and Hold
• Manual gate trigger (can be locked on)
• Course and fine-tune controls

Controls:

• S&H Button: Enables Sample & Hold, which disables the external CV IN jack and uses LFO1 and LFO2 to determine oscillator pitch. LFO1 sets the sample rate (SHAPE is ignored for this), and LFO2 is the wave that gets sampled.
• GATE Button: Manually turns on the gate so sound comes out of the synth. This control is momentary, but you can latch it on by tapping the S&H button while holding the GATE button down.
• COARSE TUNE: Adjusts the pitch of the oscillator up or down in large increments
• FINE TUNE: Adjusts the pitch of the oscillator up or down in fine increments
• SHAPE: Changes the shape of the wave produced by the main oscillator (VCO). Turning this control fully CW gives you a triangle wave. Start turning it CCW takes you through sawtooth/ramp, then at about the 12:00 position you get a square wave. Continue turning it CCW and you get several higher duty cycle square waves.
• GLIDE: Adjusts the rate at which the pitch of the VCO takes to go between pitches (whether changed by the COARSE TUNE knob or CV IN). Fully CCW causes the pitch to react almost instantly, while fully CW makes it take its sweet time.
• LFO 1 / LFO 2 SHAPE: Changes the shape of the waves produced by the low-frequency oscillators (LFOs). The shapes are similar to those of the VCO, except that the LFOs have sawtooth/ramp waves that go both up and down (since you can actually hear the difference at LFO rates).
• LFO 1 / LFO 2 RATE: Controls how fast the LFOs go.
• LFO -> VCO: Routes the two LFOs to control the pitch of the main oscillator. The 12:00 position is basically “off”, and the LFOs have no effect on pitch. Start turning the control CCW and LFO1 starts changing the pitch of the VCO. Maximum effect is at about 10:00. Continuing to turn the control starts to bring in LFO2 as well. All the way CCW gives you full effect from both LFO1 and LFO2.
• Turning the control CW from 12:00 does essentially the same thing, but brings in LFO2 first, then LFO1.
• This might seem like kind of a weird control, but it gives you quite a bit of routing flexibility with one knob. You can have no pitch modulation, LFO1, LFO2, LFO1 with a little LFO2, or LFO2 with a little LFO1.
• LFO -> VCA: Routes the two LFOs to control the amplitude of the oscillator. (See LFO -> VCO control description above for more information about how the control works.)
• ATTACK: Controls how fast the audio amplitude fades in when the gate is triggered. CCW is fast and CW is slow.
• DECAY: Controls how fast the audio amplitude fades out when the gate is released. CCW is fast and CW is slow.
• VOLUME: Controls the overall volume of the signal coming from AUDIO OUT.
• FILTER: Changes the cutoff frequency of an analog low-pass filter. Turn the knob fully CW and all frequencies (that you can hear) are let through. Start turning it CCW and the high frequencies start getting cut off, until the sound becomes muddy / muffled. Use in conjunction with the SHAPE control to get the tonal quality you are looking for.

Connections:

• CV IN: Accepts a 1 volt/octave control voltage to control the pitch of the oscillator. It responds from about 0-5V, but voltages outside of this range won’t cause damage. The CV input is quantized, so only valid (western scale) notes are played. This input is ignored when Sample & Hold is enabled.
• GATE IN: A voltage greater than about 2.5V will turn on the gate and allow audio to come out the output of the synth.
• AUDIO OUT: Connect to an amplifier or another synth. The jack has both the tip and ring connected, so you can even use stereo headphones and hear sound from both ears.
• Power: Connect 7.5-15VDC to this 3.5mm TS jack to power the synthesizer. The tip is positive (don’t worry, there’s a protection diode in case you get it reversed). You can get power from a 9V battery, AC adapter, or you may even be able to find an output on your modular synthesizer that can provide enough current.

Specifications:

• Power supply: 7-15VDC (reverse-polarity protected!)
• Power connection: 3.5mm phone jack, center-positive
• Current draw: 15ma
• Dimensions: 3.5" x 2" (the same as a business card!)