ALM ALM003 - Manual (Page 8)

Filter Section
The SID provides a multimode filter which acts on both its internal oscillator and
any external audio signal.
The filter mode can be switched cycled between low pass, band pass, high pass
and notch (low pass & high pass combined) by pressing the blue filter button. The
associated LED's will light indicating the mode.
The cut off point of the filter is controlled by the large filter control knob. The cut off
point is further offset by the control voltage input and associated uni polar attenuator
knob. A voltage applied here will further change the cut off in respect to the filter knob
position.
The resonance attenuator control behaves differently in that with no jack inserted
it acts purely to set the filter resonance. With a jack connected, it becomes an
attenuator. There is no offset control. Generally the actual resonance effect provided
by the SID is very subtle. Some SID chips exhibit the issue where low (or high)
resonance settings will actually cut audio out.
Wave shape Section
The SID provides 4 different waveform types; pulse, sawtooth, triangle and noise.
The wave shape can be selected by either pressing the associated button to cycle
through types or by applying a 0-5v to the wave shape control input.
PWM Section
With the pulse waveform selected, the pulse width of the waveform can be
controlled by adjusting the PWM knob. The pulse width can be further controlled via
the control voltage input and associated uni polar attenuator knob. A voltage applied
here will further change the pulse width in respect to the PWM knob position.
ALM-003 - ‘SID GUTS’
8