User manual

18
Accent Sweep Switch and Resonance
Here is a tabular description of the two functions of this three-position toggle switch.
Accent
Sweep
Switch
Accent
Sweep
circuit
enabled
Resonance High means the
filter will self resonate at
mid & high frequencies
when the Resonance pot is
past about 2 o’clock.
Use it for:
2 Yes Normal Acidee sounds with the
Resonance pot fully clockwise.
1 Yes High Whistly filter sweep sounds.
0 No High Self resonant filter with no
sweep on accented notes.
Overdrive, Filter Resonance and Audio Filter FM
Audio Filter FM has the most effect when the filter is most resonant. Audio signals for
Filter FM come from the Filter FM pot and from the tip of what used to be the
Headphone jack. The resonance of the filter is quenched when the filter is driven by a
heavy input signal – the filter hits its limits at the high and low extremes of the waveform
and cannot resonate at these limits. The filter can be driven hard with the Overdrive pot
and/or an external signal plugged into the Mix In socket.
On the other hand, since the internal Filter FM pot is driven by the output of the VCA,
and this VCA output signal is likely to be much higher with the Overdrive pot turned
clockwise, extreme internal Filter FM will occur, at the same time as the filter is being
overdriven by the 66.6 times normal level of oscillator signal. Seriously loud and
complex sounds!
Furthermore, if you carefully use a mono or stereo plug in what used to be the headphone
socket you can achieve even higher levels of Filter FM. Whether or not the tip of the plug
connects to anything (such as a mixer or reverb input) and assuming it is not driven by
some external signal, then you can use the tip of this plug to connect the “ring” of this
socket (Audio Out from the Filter, before the VCA/Muffler) straight to the “tip” of the
socket: Filter FM In. There is a position just a few millimetres short of full insertion
which connects the two parts of the socket together. This is different from the Filter FM
pot system in several ways. Firstly, there is no control over the level of this type of Filter
FM. (Use a proper stereo plug and lead, with external pot, mixer, gain control, etc. if you
want to control it.) Secondly, the level is potentially more intense than with the Filter FM
pot. Thirdly, this is continual FM, not dependent on “notes” via the VCA being turned
on. Finally, the polarity relationship between Filter audio output voltage and its control
voltage is the opposite of that of the Filter FM pot, so depending on the gain of the VCA,
the two may cancel to some extent, or more likely greatly complexify the final audible
result.
Rather than try to analyse and understand, its better to simply try this!
Turning up the Overdrive towards maximum, and then with Filter FM turned up high, it
is possible to have sounds which, depending on other things, descend into a spluttering