CG Products Noise VCA User manual

Modular
Noise VCA
Noise Generator with state variable VCF and VCA
1. Introduction
An all-in-one noise 'voice'. A white noise generator followed by a state-variable VCF (switchable
high-, band-, or lowpass characteristic) with adj stable resonance (Q) and a VCA makes this versatile
mod le ideal for most standard noise applications. The integrated filter provides a wide range of rich
and colo rf l noise so nds. The VCF has a 2nd inp t, allowing one to combine external a dio with the noise, or to replace the
VCF's noise inp t completely with an external so rce.
The VCA mode can be switched between exponential or linear characteristic, with a m ting option when the switch is in its middle
position; the 'Offset' knob allows one to shift the VCA's start point by adding a negative or positive voltage to the VCA's CV inp t.
2. Features
–Noise generator with integrated state-variable VCF and VCA
–3 direct o tp ts:
◦White Noise
◦S b F (Random CV)
◦VCF O t (Colo red)
–Switchable VCF characteristic:
◦Highpass
◦Bandpass
◦Lowpass
–Adj stable filter resonance (Q)
–Switchable 2nd VCF signal inp t:
◦White noise only
◦White noise & external signal combined
◦External signal only
–VCA with switchable CV mode:
◦Linear CV
◦0 (m te)
◦Exponential CV
–Available in banana or 3,5mm minijack version
–E rorack mod le
–Width: 10 HP
–Dimensions: 128,5 mm x 50,5 mm
–Depth: ≈40mm
–S pply voltage: ±12V
–Power cons mption: ≈42mA (positive rail)
Front view Left side view Right side view Banana version Drawing
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Modular
3. Functions
VCF C toff Freq ency The filter's c toff freq ency is adj stable
from ≈ 30 Hz to 15000 Hz (ca 9 ½ octaves). If req ired, the
complete range can be shifted with trimmer
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on the o ter PCB
(Please read chapter 4. Adjustment ).
White Noise O tp t Direct o tp t. The amplit de is ≈ 8-10 Vpp.
The o tp t level (and th s of the following stages) is adj stable with
trimmer
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. (Please read chapter 4. Adjustment ).
S b F (Random) O tp t Direct O tp t. This o tp t provides a
s ba dio random CV for mod lation. The amplit de is ≈8-10Vpp.
VCF O tp t Direct o tp t for the VCF. Depending on the position of
switch (VCF in), either filtered noise, a filtered external a dio
signal – inp t on socket 'ext. VCF In' - or a combination of both is
available. The filter characteristic can be chosen with the switch 'VCF
Mode' and variied with the knob Q (Resonance)
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; its freq ency
is set with the 'VCF C toff Freq ency' knob and can be
mod lated by an external CV signal applied to the 'VCF CVin' socket
(mod lation depth and polarity adj stable by knob 'VCF CVin'
and switch ) or to the 'VCF 1V/Oct.in' socket .
VCF CV In Inp t level control knob for the VCF mod lation voltage applied to the 'VCF CVin' socket
. Polarity can be changed with switch 'CV Inversion' . With the knob in f lly ccw position,
mod lation depth is 0; by t rning it CW, the mod lation depth will increase.
Q (Resonance) By t rning this knob clockwise the filter resonance increases, p to self-oscillation.
VCF CV Inp t Inversion Switch With the switch in pper position, the polarity of the inp t applied
on socket 'VCF CVin' remains the same; with the switch in lower position, the mod lation CV
gets inverted. From Noise VCA Revision 2, this switch in combination with the knob 'VCF CV in'
is replacing the polarizing potentiometer 'VCF CVin' of former versions, allowing a more precise
control of the CV inp t level and in accordance with the control elements of other CG Prod ct's
mod les.
VCF Mode Switch Selects the VCF's operation mode:
•Switch in pper position: Highpass filter (12dB)
•Switch in middle position: Bandpass filter (6dB)
•Switch in lower position: Lowpass filter (12dB)
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Modular
VCF In VCF a dio inp t selector. With this switch in pper position 'Noise', white noise is the inp t
for the filter. With the switch in middle position 'Noise+ext.' , a combination of white noise and the
external a dio signal applied on the 'ext. VCF In' socket feeds the filter's inp t. With the switch
in lower position 'ext.', only the external a dio signal is being processed by the VCF.
VCF CV Inp t VCF c toff freq ency mod lation inp t. Mod lation depth can be adj sted by knob
'VCF CVin' ; its polarity is invertable with switch .
VCF 1V/Octave CV Inp t The 1V/oct. tracking can be adj sted precisely by trimmer
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and
trimmer
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(HF-trim) on the o ter PCB (Please read chapter 4. Adjustment )
Ext. VCF In 2nd external signal inp t for the VCF. This inp t allows an external a dio signal to be
fed into the VCF. This signal may replace the internal noise so rce or can be combined with it;
depending on the position of switch 'VCF In' .
Note: This socket has no extra knob for adj sting its level. D e to the wide range of possible inp t
signals and filter settings it may happen that the filtered signal is distorted (with high Q setting and
an inp t freq ency which is nearby the VCF's c toff freq ency) or is too low.
VCA CV in Inp t level control knob for the CV so rce applied on 'VCA CVin' controlling the
VCA's amplification (for its inp t signal selectable by switch 'VCA In' ) . In center position (denter
locked) the level is 0 and there is no CV mod lation of the VCA. By t rning the knob clockwise, the
CV will mod late the selected inp t signal. By t rning this knob co nterclockwise, the inverted CV
mod lates the VCA's inp t signal ('polarizer').
Offset VCA offset control. With this polarizing control knob either a positive or negative voltage can
be added to the VCA's CV inp t. In center position (denter locked), the offset voltage is 0. By
t rning the knob CW, a positive voltage with range p to +5V will be added, by t rning the knob
CCW, a negative voltage p to -5V is addable. By t rning this knob CW, the p re, nmod lated
VCA's inp t signal (selectable by switch 'VCF In' ) will be provided on the VCA's o tp t 'VCA O t'
- with variable amplification. In combination with an applied CV on 'VCA CVIn' , a negative
offset voltage added (t rning the knob CCW) may be sed to shift the VCA's operation point – so
that only from a certain amo nt of positive inp t CV begins to open the VCA (Example see chapter
6. Patches Example 4).
VCA In Signal inp t selector for the VCA. The position of this switch determines which signal is
being processed by the VCA.
•Switch in pper position: White noise
•Switch in middle position: S b F (Random)
•Switch in lower position: VCF O tp t
VCA CVin Control voltage inp t for the VCA. The amo nt and polarity is adj stable with knob 'VCA
CVin' .
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Modular
VCA Mode With this switch the VCA's operation mode can be selected between linear CV or
exponential CV processing and 0 (m te):
•Switch in pper position: Linear
•Switch in middle position: 0 (m ting)
•Switch in lower position: Exponential
VCA O t O tp t socket for the VCA. The position of switch 'VCA In' decides, which inp t signal
is being processed; controllers 'VCA CVin' (for socket 'VCA CVin' ), 'Offset' and switch 'VCA
Mode'
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are responsible for the CV processing.
Audio routing
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Modular
4. Adjustment & Settings
1. General Adjustments
1. White Noise Level
The internal white noise so rce's level is set with
trimmer
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. By defa lt, it is adj sted for an o tp t
amplit de of ≈10Vpp on o tp t 'White' .
Note: When changing the setting of this trimmer, also
the noise o tp t levels of 'S b F' , 'VCF O t' and
'VCA O t'
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will be affected.
2. VCA O tp t Level
The VCA's o tp t level on socket 'VCA O t' can be
adj sted by trimmer
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. By defa lt, this val e is set
so the level of the o tp t is almost the same as the
level of the direct o tp ts , or - with the VCA
offset knob f lly t rned p clockwise (eq ivalent
wo ld be a CV of +5V applied on 'VCA CVin' and
knob 'VCA CVin' f lly t rned p cw).
3. Freq ency range
With trimmer
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the entire freq ency range of
potentiometer 'VCF C toff freq ency' can be
shifted. By defa lt, the trimmer is adj sted for a
lowest VCF c toff freq ency of ≈ 15Hz.
2. VCA Adjustments
The Noise VCA is already caref lly adj sted. No f rther calibrations sho ld be needed. In case of e.g.
nintentional adj stment, here a description of the req ired trimmers and adj stments (o ter PCB):
1.Linear (common) 0-point
This trimmer
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(on inner pcb) determines the VCA's CV 0-point. With switch 'VCA Mode'
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in pper
position ('lin.'); switch 'VCA In' in pper position ('White'), the 'Offset' knob in middle position
(center locked) and no CV applied, the VCA's o tp t (socket 'VCA O t' ) signal sho ld be as q iet as
possible with no white noise signal passing thro gh, b t the 'Offset' knob sho ld still react sensitively
when t rned CW.
2. Exponential 0-point
Adj st the exponential converter's 0-point with trimmer
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. With the 'VCA Mode' switch
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in lower
position ('exp'); the 'VCA In' switch in the pper position ('White'), the 'Offset' knob in the middle
position (center locked) and no CV applied, the VCA's o tp t signal on 'VCA O t' ) sho ld be as q iet
5

Modular
as possible with no white noise signal passing thro gh (compare to when switch 'VCA Mode'
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in
middle position ('0'), b t the 'Offset' knob sho ld still react sensitively when t rned CW and the white
noise signal sho ld increase slightly on the VCA's o tp t).
3. Exponential Gain
The trimmer
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adj sts the exponential converter's amplification. With 'Offset' knob t rned f lly cw,
the o tp t vol me of the VCA sho ld be the same both in 'lin.'and 'exp.' mode (compare by toggling
switch 'VCA Mode'
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). With this trimmer yo can adj st the VCA's vol me in 'exp.' mode.
4. CV Feedtro gh on VCA O tp t
With trimmer
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the feedtro gh of the mod lation CV applied on 'VCA CVin' can be set to its
minim m.
3. VCF Adj stments
The Noise VCA is already caref lly adj sted. No f rther calibrations sho ld be needed. In case of e.g.
nintentional adj stment, here is a description of the req ired adj stment proced re:
1. Connect the o tp t 'VCF O t' to an amplifier. With switch 'VCF In' in lower position
('ext.' ) / no external signal applied on and 'Q' knob
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f lly t rned clockwise, the filter will
become self-oscillating.
2. T rn trimmer
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ccw p to its end – the freq ency sho ld getting lower and lower ntil it
remains. Then t rn the trimmer ca 3 ro ndings clockwise.
3. Connect both a calibrated VCO and the Noise VCA's 'VCF O t' to yo r mixer or so ndsystem,
listening sim ltaneo s to both freq encies, and bring them in t ne on a middle-range note.
4. Apply a CV so rce, e.g. a keyboard, to both device's 1V/oct. inp t (Noise VCA: Socket );
bring the oscillations in t ne again.
5. Play or generate 2 alternating notes ( with a distance of 3-4 octaves); e.g. 200 Hz and 1000
Hz and calibrate trimmer
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ntil the tracking is best; if necessary, bring the gro nd-notes of
both oscillators in pitch again.
6. If necessary, slightly readj st trimmer
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(HF-trim).
4. Bus CV
J mper "JP1" in "off" position (PCB ): The B s CV is
not connected.
J mper "JP1" in "on" position (PCB side): The B s
CV is controlling the VCF's c toff freq ency.
6

Modular
.Patches
Simple patches (with other CG Prod cts' mod les)
Patch Description A dio Link
1. Peak & Hold is controlling the Noise VCA
In this standard patch the Peak&Hold's
'Release' o tp t controls the VCA with a
dynamic envelope shape, while the
Peak&Hold's 'P+H' o tp t is mod lating the
VCF's c toff freq ency.
Peak&Hold inp t:
Dr m machine
http://www.cg-
prod cts.de/A dio/NoiseVCA_P
-H528.mp3
2. 2 So nds combined
In this example the XR22 VCO FT's
sq arewave o tp t is applied to 'ext VCF In';
the Peak&Hold is mod lating the Noise
VCA's VCF c toff freq ency and the VCA.
Peak&Hold inp t:
Dr m machine
http://www.cg-
prod cts.de/A dio/NoiseVCA_X
R22_PH-530.mp3
3. VCF triggered with imp lses
Short imp lse signals can be sed to trigger
the VCF, generating 'ping' like so nds. Here
the Peak&Hold's imp lse o tp t is sed to
trigger the VCF; its 'P+H' o tp t is
mod lating the filter's c toff freq ency.
Peak&Hold inp t:
Dr m machine
http://www.cg-
prod cts.de/A dio/NoiseVCA_V
CFtriggered-535.mp3
4. VCF & VCA working independently
When sing the VCA with white noise (or
S b F) as signal so rce, the VCF can be sed
completely independent to process another
signal; or the VCA can generate dynamic
accents to the 1st (VCF) a dio o tp t - by
shifting the VCA's offset level. Here the
VCF's a dio inp t is the imp lse-triggered
Delay 1022.
Peak&Hold inp t:
Dr m machine
http://www.cg-
prod cts.de/A dio/NoiseVCA_
Delay1022_PH-0539.mp3
5. Sb F mod lating CVs
The 'S b F' o tp t can be sed to mod late
the VCF c toff freq ency and/or the VCA -
random so nds s ch as 'th nder' or
'crackling' can be generated.
http://www.cg-
prod cts.de/A dio/NoiseVCA_S
bF-542.mp3
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Modular
6. Contact & Support
Christian Günther
Forster Str. 50
10999 Berlin
info@cg-prod cts.de
www.cg-prod cts.de
Phone: ++49 30 61286299
Mobile ++49 178 7699267
Prod ct webpage: http://www.cg-prod cts.de/mod le/noisevca/
This is Revision 2.0
Doc mentation for Rev.1 (with another control element arrangement on the panel, no C toff-F CV
inversion switch and different trimmers on the o ter pcb) please see here:
http://www.cg-prod cts.de/Noise-VCA_doc mentation-Rev.1.pdf
Doc mentation for Rev.0.9 (With some different trimmers on the o ter PCB) please see here:
http://www.cg-prod cts.de/Noise-VCA_doc mentation-Rev0.9.pdf
© Christian Günther 2019
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