Audiospektri PGV Manual - Page 2

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The abbreviation PGV stands for Parametric Guitar Vocoder denoting the difference from a traditional vocoder
that merely modulates the guitar signal based on the vocal spectrum. The PGV instead does an analysis of the
guitar signal, and measures the pitch and amplitude of all the individual strings. Based on that data, the PGV
does independent synthesis for all the found six string signals, based solely on the vocal spectrum, and
allowing controlled modification of the analyzed parameters. This opens up possibilities for such special effects
as described in this manual. In addition, the PGV also is a versatile guitar interface for any Eurorack system
even without the vocal input, because it also includes "pilot" oscillators for each string, i.e. it outputs modulated
sinewaves in the string pitch notes.They can be fed to other Eurorack modules for further processing.
There are four 3.5mm jack I/O connections in the module: the guitar in and out are mono TS jacks, while the
pedal and microphone jacks are three contact TRS jacks. We have found that using the electric guitar's neck
pickup (humbucker in our case) produces the best results.
Use only such an expression pedal that has the potentiometer slider output at the tip of the TRS plug (e.g. in
the M-Audio pedal, switch in the "M-Audio" position).
A dynamic vocal microphone input jack has the hot signals at the tip and ring contacts, and grounded sleeve.
For a more common XLR microphone connector you need to use a proper XLR to TRS adapter.
From the rack connector, only the +15V source is used, the current requirement is 150mA.
The 3-way "pedal effect select" switch is used to select which of the special effects is being controlled
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by the expression pedal. For the three control alternatives, there are also three potentiometers in the
upper row of controls, "vibrato", "VCF", and "spectrum shift". When the switch is used to select one
of the three alternatives, it disables the corresponding knob for the same function in the case of "VCF",
and "spectrum shift", e.g. if one selects the "VCF", the effect is controlled by the pedal, and the
"VCF" potentiometer has no effect, and correspondingly for the "spectrum shift" position. On the
other hand, the "vibrato" knob is only functional when the 3-way switch is in the "vibrato" position.
The functions of the various controls are described later in detail.
The "spectrum hold" -toggle switch allows the freezing of a momentary spectrum (any vowel) from the
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vocal microphone, when flipped to the "on" position. The user also needs to adjust the "noise gate /
pilot gain" knob up from the counter clockwise location to determine the threshold level, above which
the spectrum freeze can be triggered. For the noise gate, the lower half of the knob range is used.
The transpose -1 octave switch drops the measured guitar pitch down one octave, when in the "on"
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position.
The large volume potentiometer controls the analog output amplifier; the maximum level will be about
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7V pp, AC connected, ready to feed other Eurorack modules from the single-ended output jack.
The "noise gate / pilot gain" -knob has three functions:
1. For the vocal microphone signal, the background noise can be suppressed below the level set by the
knob. It works from the counter clockwise to the middle position.
2.
It determines the capture threshold level for the "spectrum hold" -function as described above.
3.
From the center location to full clockwise position, the knob controls the "pilot" signal volume. The pilot
signal is an additional synthetic output signal that is generated corresponding to the note pitch
frequencies of the guitar strings. See later sections on how it can be utilized.
The "mic gain" knob controls the volume of the vocal microphone signal, together with the guitar signal
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amplitudes, and the signal compressor logic, see the later section on how it works.
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The connections
The controls