Testing, testing, 1, 2, 3...
Apply power to the unit making sure you are applying the power correctly. Check that no
device is running hot. Any sign of smoke or strange smells turn off the power immediately and
recheck the polarity of the power supply, and the direction of the ICs in their sockets.
Assuming everything is OK so far, it is time to apply an audio input. Use a bright signal like a
sawtooth output from a VCO. Middle A, 440Hz is a good note to use.
Moving the FREQUENCY control should produce the usual and distinctive filter effect from
the low pass output. From the high pass output, you should hear the sawtooth get brighter and
less smooth as the cut-off frequency is increased. The band pass output should produce a sort
of wah-wah sound as the Frequency pot is moved back and forth. The notch output will be
more subtle, and will appear to sound like a mild phasing effect. Turning the Resonance up
will accentuate the ‘electronic’ nature of the sound on all four outputs.
Remove the audio input and ensure the RESONANCE mode switch is set to HIGH. Check
that at maximum resonance the filter output will oscillate across the whole audio band. You'll
probably need to turn up the cut-off frequency pot to above the mid-point first to actually get
the SVF to start to oscillate – it does not tend to oscillate naturally at frequencies below 1kHz
or so. Beware, it is quite possible to get this filter to oscillate above the range of hearing. So
be careful so as not to damage your studio monitor’s tweeters.
Now click the MODE switch to NORM and you should find that the loudness of the
oscillation drops somewhat. It will also probably cease to oscillate at all at frequencies below
800Hz or so.
Listening to the band pass output with the sawtooth input still connected, patch a LFO or EG
output to the CV inputs. The 1V/octave input should produce large sweeps of cut-off. Check
also that with the LFO or EG connected to the CV1 input, the CV1 pot allows you to control
the depth of the sweep. Fully clockwise the CV1 input should produce very deep sweeps.
Notice that the minimum sweep depth should occur with the CV1 pot at its mid point. Use a
sawtooth waveform on your LFO, and see if the CV1 depth pot allows you to invert the
modulation input. You should get a ‘dow-dow-dow...’ from one side and a ‘yit-yit-yit...’ from
the other.
Check that both the audio inputs behave identically.
If all this happens, the chances are that you have a working module. Now before you start to
use it in your modular you will need to calibrate it. The full calibration procedure can be found
in the User Manual.
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