Joranalogue audio design Filter 8 User Manual
FILTER 8
OSCILLATOR
MULTIMODE FILTER/8-PHASE
INTRODUCTION
Representing the cutting edge in modular analogue voltage controlled filter (VCF) design, Filter 8 offers more possibilities and higher fidelity in 12 HP than ever before.
Starting from the classic OTA-style 4-pole
cascaded lowpass (LP) topology, Filter 8 features
separate LP outputs, each with their own
character. Additional filter responses are
achieved by pole mixing: 1-pole highpass, a
special band boost and notch response, phase
shifter and 4-pole bandpass. All outputs are
available simultaneously.
Key to Filter 8's performance is the innovative
resonant feedback circuit. By increasing the
resonance, all outputs will resonate at the filter
frequency, without any low frequency response
loss. At higher resonance levels, self-oscillation is
achieved, turning the module into an excellent
8-phase sine wave voltage controlled oscillator
(VCO) with temperature and switchable gain
compensation, low distortion, constant
amplitude and accurate frequency tracking over
at least 5 octaves. At sub-audio frequencies,
Filter 8 can function as an 8-output voltage
controlled slew modifier or 8-phase low
frequency oscillator (LFO).
CONTENTS
In the Filter 8 box, you’ll find:
Product card, stating serial number and
production batch.
16-to-16-pin Eurorack power cable.
Mounting hardware: two black M3 x 6 mm
hex screws, two black nylon washers and a
hex key.
The Filter 8 module itself, in a protective
cotton bag.
If any of these items are missing, please contact
your dealer or support@joranalogue.com.
Simultaneous exponential and linear frequency
modulation is possible, for classic FM tones or
chaotic modulation. A hold feature is also
provided, 'freezing' the output voltages manually
or under gate control. This is useful for halting
modulations, or as a sync-like effect at audio
frequencies. The dedicated ‘ping’ input allows
you to easily create crisp percussive sounds with
different timbres.
While rooted in the legacy of classic synthesisers,
Filter 8 provides a new approach to musical
signal generators and modifiers: instead of
simply a VCF, VCO, slew modifier or VCLFO, a
single analogue module can now be any of those,
and anything in between.
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FILTER 8
OSCILLATOR
CONTROLS & CONNECTIONS
1 FREQUENCY RANGE SWITCH
This switch determines over which frequency
range Filter 8 will operate: low frequency (slew
modifier/VCLFO) or audio frequency (VCF/VCO).
2 COARSE AND FINE FREQUENCY KNOBS
The filter/oscillator frequency is determined by
these knobs. In standard audio mode, with the
fine knob centred, the coarse knob has a range
of 22 Hz to 22 kHz. The fine knob’s range is 5 % of
the coarse knob (6 semitones in audio mode).
In low frequency mode, the total range is
2.8 mHz (a period of 6 minutes) to 180 Hz, with
1 Hz when both knobs are centred.
MULTIMODE FILTER/8-PHASE
3 RESONANCE KNOB
The resonance knob controls a feedback path
from the filter output back to the input, causing
the filter frequency to be emphasised. Filter 8’s
design includes an innovative resonance circuit:
by increasing this parameter, all outputs will start
to resonate at the filter frequency, without any
low frequency response loss.
At higher feedback levels, self-oscillation will be
achieved, turning the module into an excellent
8-phase sine wave VC(LF)O.
4 VOLT PER OCTAVE FM INPUT
This input is used to modulate the frequency in
an exponential fashion, with a standard 1 volt per
octave response. This enables accurate audio
pitch in filter or oscillator mode. In the low range,
the sensitivity is increased to approximately 0.66
volt per octave.
5 EXPONENTIAL FM INPUT AND KNOB
This second exponential FM input includes a
polariser knob to set the modulation depth, with
0 in the centre, +1 volt per octave maximum and
−1 volt per octave minimum in audio mode. In
low mode, the sensitivity is increased to
approximately 0.66 volt per octave.
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FILTER 8
OSCILLATOR
6 LINEAR FM INPUT, KNOB AND AC SWITCH
In addition to standard exponential FM,
simultaneous linear frequency modulation is
possible as well. This form of FM is well-known for
being more ‘tonal’ in VCO mode, limiting the
perceived shift in fundamental pitch as the FM
depth is increased.
This FM input also features a polarised depth
knob. The sensitivity ranges to approximately
±7 % frequency deviation per volt.
Enable the AC switch to AC-couple the LFM
input. This rejects any DC offset or very low
frequency content that may be present in the
modulation signal, preventing a fundamental
pitch shift from appearing during audio rate
modulation.
7 RESONANCE MODULATION INPUT AND
KNOB
The resonance amount can be modulated
through this input, with +5 V corresponding to
maximum resonance. The modulation knob
range is bipolar, just like the FM inputs.
MULTIMODE FILTER/8-PHASE
9 SIGNAL INPUTS
Connect the signal(s) to be filtered here. These
identical inputs are mixed together, which can
simplify certain patches as it often removes the
need for a separate mixer module.
Filter 8 can clip and distort with certain input
signals, especially if they are high-level, rich in
harmonics and resonance is added. This is
because all outputs are unity gain (when
compensation is disabled), and removing
harmonics can actually result in a signal’s
amplitude rising. This distortion can be used as a
deliberate sonic effect. If you prefer to avoid it
however, simply lower the amplitude(s) of the
input signal(s).
To use Filter 8 purely as an oscillator, simply set
the resonance to maximum and leave the input
sockets unpatched.
8 GAIN COMPENSATION SWITCH
By default, each output is at unity gain with
respect to the signal inputs. This is very useful
when processing audio or CV. However, when
Filter 8 is used in oscillator mode, all outputs
resonate at different amplitudes. For this reason,
the outputs are equipped with gain
compensation stages, enabled using this toggle
switch. With the compensation turned on, all
output signals will have the same amplitude.
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