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!
Trimming
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.
Scale
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)