BASTIL Instruments TROMSO Instructions

Tromsø is a combination of 3 basic utility modules: VCO,
TROMSØ
Comparator and Sample & Hold. Internal normalisation
allows you to instantly use it as voltage controllable
VCO+comparator+S&H
analog downsampler (or sample rate reducer, if you like).
The s ample rate is set by VCO Rate and a sort of "dry/wet"
mix effect which is achieved by adjusting the Threshold
when in the Track & Hold mode.
VCO
This architecture was inspired by a machine called
) Distortotron, made in 1994 – arguably the first analog
downsampler and bit distortion of its kind. That machine
LFO
came from a collaboration between Norwegian musician
Mental Overdrive based in Tromsø and the inventor group
)
Psybe (Svein Berge and Henrik Sundt). It was created from
a need to bring back oldschool sampler aliasing and lo-fi
effects and it heavily influenced the sound of the album
T&H
Plugged, which is the landmark of the so called Tromsø
)
sound.
S&H The VCO of the Tromsø module can track one volt per octave
when the Attenuator on the FM input is fully open, which
makes it possible to have the downsampling effect track
V/OCT the pitch of a played note. All 3 utility modules of Tromsø
)
)
can also be used independently. Internal normalisations are
Ø
disconnected when using the input jacks.
)
V
C
O
)
instruction
FM TRIANGLE
)
C )
M
P
RTR
THR IN
Triangle core VCO with Triangle output of +/- 5V
amplitude.
)
)
GATE OUT
)
The rate of the VCO is set by the VCO RATE knob and
the Range of the VCO is set by the switch. In VCO Range
the frequency goes from 2Hz to 45kHz and in LFO Range
IN OUT
from 50s to 50Hz. With strong negative voltages at the
FM input, the rate of the VCO can go even lower.
)
The control voltage for the pitch of the VCO is the sum
of the position of the VCO RATE knob and the voltage on
the FM Input going thru the Attenuator Knob. When the
Attenuator knob is fully CW, the FM input tracks 1V/Oct
over more than 5 octaves and has an input impedance
of 100k ohms.
)
The comparator section has 3 connectors and a Threshold
knob. A Comparator is a device which takes two voltages,
compares them and outputs a HIGH gate, if one of
the voltages is greater than the other. In the case of
Tromsø, if the voltage at the CMPRTR IN is greater than
the THRESHOLD voltage, it outputs a HIGH gate. The
THRESHOLD voltage is the sum of the position of the
Threshold Knob (range of +-6 volts) and the voltage on
the CMPRTR THR input. The Triangle output of the VCO
is normalised to the CMPRTR IN, which means that the
CMPRTR OUT creates a standard pulse waveform from
the VCO (with amplitude approx. +/-5 volts).
)
The indication LED is driven by the CMPRTR OUT signal.
)
Sample and Hold (S&H) is an analog voltage storage
device. It looks at voltage at the S&H INput at a given
time (rising gate on the S&H GATE input ) and
remembers that voltage and keeps it at the S&H OUTput.
This simple device is hugely useful for a great amount of
unique techniques of modular synthesis, especially when
combined with other modules
)
The S&H circuit has two modes, selectable with
a switch. S&H mode was described above. The Track
and Hold (T&H) mode is a variation of the S&H circuit.
The difference is that while there is a HIGH GATE, it lets
the INput signal through to the Output (it tracks the
signal) and at the falling GATE, it remembers the last
voltage at the input and holds that voltage until there is
another HIGH gate. See the diagram to wrap your head
around it!
Signal Input
Gate Input
Signal Output
Sample and Hold
Signal Output
Track and Hold
)
Normalisations within Tromsø allow it to be simply used
as Voltage Controllable Downsampler, but once you plug
cables into the normalised inputs you can use the VCO,
Comparator and S&H sections independently. The Triangle
output of the VCO is normalised into the Comparator
input and the Comparator output is normalized to the
S&H Gate input. This is indicated by the arrows on the
front panel.