Nord Modular G2 handleiding
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10. Technical reference: Voice allocation and polyphony NORD MODULAR G2 V1.4x
Page 138
E
XPERIMENT
!
You can always try to Patch the three different types of signals to wherever you want. You may run into
situations where the result of a connection will not be what you expected, but that is part of the charm
of any modular system. A blue control signal output can be very useful for modulating a yellow logic
signal input, and an audio signal output can certainly produce interesting results connected to a control
signal input or a logic signal input. The colors are only there to help you identify the various signal types,
not to restrict you in any experiments.
VOICE ALLOCATION AND POLYPHONY
The G2 system uses
DSP
-chips to generate the sound. These chips are computer chips specialized in
doing the type of calculations used in sound synthesis.
DSP
-chips work like computer processor chips in
a way that they can do only one calculation instruction at a time, like a multiplication instruction (e.g. used
for the down scaling function of a knob) or an addition instruction (e.g. used for mixing two signals).
Basically all modules and cable connections in each voice appear internally as a piece of
DSP
programming
code that needs to be executed to actually generate sound. This piece of code is a string of
DSP
instructions that are executed one after another. For every output sample of the G2, and there are 96
thousand samples a second, the piece of code for each voice needs to be executed completely. The more
modules there are and the more complex each module, the more instructions will be needed and the
longer it will take to execute the piece of code. There is a limit to the total amount of instructions that
can be executed in the available time. The amount of instructions within the piece of code for one voice
determines the available polyphony, or how much time is left for execution of code for more voices.
When the piece of code is short it can be executed many times within the time frame of one output
sample, so there can be many voices. But if the piece of code is very long there might not be the time to
execute it for a lot of voices, so polyphony will drop to what just fits fully in the available time. The G2
has four
DSP
-chips or eight chips with the expansion board fitted and in the G2X model. The
DSP
-chips
work in parallel, meaning that if one voice takes all the resources of one
DSP
the polyphony would be
four voices, or eight voices with an expansion board. Note that a single voice cannot exceed the code
that fits in one
DSP
-chip. The FX Area can also use up to one
DSP
, and if this is the case the minimum
polyphony is three voices plus effects or seven voices plus effects in an expanded or G2X model. The
Patch Load indication shows the percentage of available calculation time claimed by one voice. In
practice the average polysynth voice can be modelled within 25% to 33%, and a ‘luxury’ polysynth model
with more than two oscillators within 50%. When a voice uses 100% you can be sure that only a single
key could give a truely massive sound, but at a price of limited polyphony. These 25%, 33% and 50% are
‘magic numbers’ when it comes to setting the amount of polyphony, as these are the percentages where
the system will suddenly drop voice count. E.g. when in a patch the Patch Load percentage is increased
from 33% to 34% the polyphony will drop from 12 to 8 voices on an unexpanded system (3 times 34%
does just not fit fully into 100% any more).
The Memory display indicates the memory which is used directly by a
DSP
-chip. The
DSP
-chip can access
two types of memory, internal memory in the
DSP
-chip itself and 256 kWord of 24-bit
RAM
memory. The
internal memory is used to store the output values of each module in a patch. The
DSP
-chip has room to
store over a hundred module output values and this also sets a limit on polyphony. E.g. when a patch
uses about 40 outputs on its modules the internal
DSP
memory load is just under 33% and this would
allow 12 voices or 24 voices on an expanded system or on the G2X model. Even if the Patch Load is e.g.
24% the used memory of 33% would set the polyphony limit in this example. To get an idea of the
possible polyphony, always look at which display shows the highest value, the Patch Load or the Memory
display. The one with the highest value will set the limit. When the Memory percentage exceeds the Patch
Load percentage and you need to save just one percent of memory to be able to increase voice count, try
to use modules with less outputs. E.g. try to use an ADSR module instead of an ADR module, as the
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Productinformatie
| Merk | Nord |
| Model | Modular G2 |
| Categorie | Niet gecategoriseerd |
| Taal | Nederlands |
| Grootte | 60689 MB |
