Signal generator board (from Starter Kit)

The prototype version of the board. There are a few differences compared to the final board.

This board contains a full blown VCO plus a simple non-voltage controlled LFO. It is designed to be part of the AMORE Starter Kit but can also be used by itself. It is NOT an AMORE plug-in module.
The VCO-part is a clone of the VCO in the ARP 2600. This VCO delivers sawtooth, pulse and triangle waves on separate jacks. There are inputs and amount knobs for frequency modulation and pulse width modulation. There is also a switch that changes the VCO frequency range from audio to LFO so you can use it for modulation, just like on the ARP 2600. But in addition, there is also a separate non-voltage controlled LFO which outputs triangle and square waves on separate jacks. The LFO has it's own rate knob.
The signal generator board is fully self-contained, with all potentiometers and jacks on-board. It only needs an external power supply and there is a dedicated connector for this on the board. You could use this board as a VCO/LFO board in a standalone synth. Built according to the description it does not feature temperature compensation, however. If you require this, you could substitute the 2 kohm resistor with a 2 kohm tempco resistor and put this in thermal contact with the PNP/NPN transistor pair nearby.

This module uses the CA3046 transistor array, which can be somewhat difficult to find but is in fact still available from specialist suppliers. One of them is Das Musikding in Germany. They are not expensive, so buy some extra for future modules while you're ordering!


There are five trimmers on the board:

Saw offset
Adjust this so that the VCO sawtooth wave is symmetric around 0 volts.

Tri adjust
Adjust this to make the triangle waveform look as good as possible.

Tri offset
Adjust this so that the VCO sawtooth wave is symmetric around 0 volts. Not that adjusting the offset will change the waveform so you will have to readjust these two settings until both the waveform and the offset is OK.

Freq trim
Adjust this so that the VCO has a frequency range of approximately 20 Hz to 20 kHz when turning the frequency knob all the way.

This will only hade to be adjusted if the VCO is supposed to track 1 octave/volt. For use as a test tone generator this is normally not necessary. If you require this, you will have to connect a voltage of exactly 1, 2, 3, 4, 5 volts etc. to the KOV input and chek that the frequency doubles for every volt.

Skill level required: LOW

There isn't anything particularly difficult on this board.

Circuit board layout (PDF-file)

Component placement (PDF-file)