2/8/2021
Norand Mono Manual
localhost:3000/manual
9/23
Filter block
Mono’s lter is a resonant lter with low-pass, high-pass and band-pass
output. Like the oscillator, it is a unique design : discrete integrator cells
arranged in a three cell 18dB slope state-variable lter. It features a stable
self oscillation at maximum resonance and it is precisely tuned like the
oscillators. When driven hard, it saturates the input signal asymmetrically ·
only the negative voltage is clipped ·.
The [CUTOFF] parameter sets the frequency, from C-1 to C10. Although
you won't necessarily hear it because it is smoothed, the lter knob is
quantized to semitones (just the knob, not the modulations). This is a
controversial feature, but this is the only way to make the lter resonance
perfectly tuned with the oscillator.
The [RESONANCE] parameter goes from a very attenuated cuto point to
self-resonant, with lots of nice things in the middle. The resonance peak is
quite shallow, which allows the user to “scan” the harmonic content of the
input when swept.
The [COLOR] parameters continuously fade from band-pass, to low-pass,
to high-pass output. On these types of continous outputs, you’ll usually
nd band-pass in the middle, but I nd that quite boring, so there’s that.
There are some very interesting timbres in between each output. For
example, put the knob halfway between low-pass and high-pass, and you
get a resonant all-pass lter !
The [FOLLOW] key toggles keyboard follow : when enabled, cuto
frequency is linked to the current note pitch.
Finally the [ENV AMOUNT] parameter adjusts how much of the main
envelope contour is applied to the cuto frequency parameter. It’s bipolar :
no e ect in the center position, positive envelope in the clockwise
direction, and negative envelope in the counter-clockwise direction.
FM (Frequency Modulation) is a very deep subject with whole
books written about it, I’ll do my best to explain it shortly. Let’s
start with what FM is : the output of one oscillator · the
modulator · is used to control the frequency of another
oscillator · the carrier ·. This will in turn enrich the harmonic
content of the carrier, by e ectively “spliting” each of it’s base
harmonic. There are two main type of FM : exponential and
linear. Unlike exponential FM, linear FM can reach zero hertz,
which basically stops the oscillators, which is not very pleasing
in term of musicality. Thru-zero FM alleviate this problem by
introducing “negative” frequency. When the oscilator reaches
zero hertz, it will reverse it’s cycle and start oscillating
backward, and when it crosses zero hertz, it will reverse again
back to “positive” frequencies. Note that I put negative and
positive in quote, in the real world there is no such thing as
negative frequency.
