Weston Precision Audio 2V2 User manual

© 2022 Weston Precision Audio
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2V2
Dual Analog Oscillator
Eurorack Module
User Manual
Weston Precision Audio
Designed In Portland, Oregon
Revision 01 - July 20, 2022

DESCRIPTION
2V2 is a dual voltage controlled
oscillator (VCO) module in Eurorack
format. This VCO is available as a pre-
built unit as well as a Through-hole DIY
panel and PCB set. This document is the
user manual for the pre-assembled unit.
However, the functions described,
except for the trimmer locations, are the
same for the DIY version and the
prebuilt version.
2V2 contains 2 analog triangle-core
VCO units. Each VCO core on 2V2 is
functionally identical, with the exception
that VCO B contains a small bit of extra
circuitry that allow it to be sync’d (both
“hard” and “soft”) to VCO A.
Additionally, each VCO may be
switched to LFO (low frequency
oscillator) operation.
Both VCOs can be modulated externally
in a standard exponential manner, as
well as “through zero” linearly. There
are also 2 VCAs on board for shaping
FM modulation with an external
envelope or signal!
2V2 has been engineered using
temperature-compensated VCA modules
so that it is extremely stable under
ambient temperature changes. Each
VCO is capable of good VCO tracking
over 7 octaves or more. Each VCO
contains the “standard” host of outputs
(triangle, sine, pulse, saw), as well as
sub-octave square outputs.
SPECS
Module Size: 16HP
VCO Output (All outputs ~1kOhm
Impedance): Triangle, Square, Sub-
Octave Square, Sawtooth and Sine.
Inputs (All inputs >=100kOhm
Impedance): Volts/octave, FM,
Envelope In.
All individual wave outputs: 10 Volts
peak-to-peak nominally.
Power input: +12V & -12V via standard
10 pin Eurorack connector.
Power consumption (+12V / -12V):
Typ: 115mA / 85mA
Max: 125mA / 95mA
MAXIMUM LIMITS
Supply Voltage: +13.5V / -13.5V
Any inputs: Supply limits.
© 2022 Weston Precision Audio
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MAIN CONTROLS & I/O
Each VCO is functionally identical and
contains the same inputs and outputs.
Thus, one can simply draw and
imaginary vertical line down the center
of the module. Everything on the left
side is the same as the right.
Tuning:
These are standard tuning pots, the
upper one being a very coarse
adjustment, and the other being a fine
(about 27:1 ratio) adjustment.
1 V/Oct Input:
This is a standard 1 Volt per Octave
input for pitch control of the VCO.
LFO Button:
This is a toggling-type button, which
when depressed will cause the amber
LED next to it to light, and that VCO’s
core will oscillate about 0.015 of the
frequency as in normal mode and thus
become an LFO (Low Frequency
Oscillator)
FM Input:
This is the input for Frequency
Modulation signals (FM). The switch
immediately to the right (or left for the
right-hand VCO) selects whether the
modulation will be exponential in
response, or through-zero linear.
FM Amount Potentiometer:
The pot to the right of the FM input
shown above (or to the left for the right-
hand VCO) attenuates the amount of
signal sent to modulate the VCO.
Env In Input:
A signal inputted here will modulate the
*amount* of signal sent to modulate the
VCO. The overall amount of modulation
is still governed by the FM amount pot.
The input could be an envelope or any
other signal, but it must be unipolar (0
to 5V for 0% to 100% modulation).
Larger voltages can be inputted to “Env
In”, but the FM-shaping VCA cuts off at
100%, which is about a 5V input to “Env
In”
© 2022 Weston Precision Audio
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PW Potentiometer:
This pot adjusts the nominal pulse width
of the Pulse output of each VCO core
from 0 to 100%, with the center (high
noon) position being 50% or a square
wave.
WAVE OUTPUTS
Each VCO core has 5 outputs. From top
to bottom, left to right:
Sine:
An approximate sine wave formed by
feeding the triangle output to an
overdriven matched differential pair
circuit.
Triangle:
The triangle wave from the VCO core.
Sawtooth:
Sawtooth wave converted from VCO
core’s triangle and square outputs.
Pulse:
A standard pulse output from feeding a
PW + PWM signal and the triangle to a
comparator.
Sub-Octave Square (1/2f):
A square wave of 1/2 the frequency of
all the other wave outputs.
SYNCING AND MODULATION
Using the 3-position sync switch, the
right-hand VCO core can be synced to
the left-hand VCO core. In the center
position, sync is disabled. In the upper
position, the right VCO is “soft-synced”
© 2022 Weston Precision Audio
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to the left, meaning the triangle reverses
on each positive zero-crossing of the left
VCO. In the lower position, the right
VCO is “hard-synced” to the left,
meaning that the capacitor is discharged
to zero on each positive zero-crossing of
the left VCO. The following scope shots
show the difference. The blue wave is
VCO A (left VCO) and the red wave is
VCO B (right VCO):
Hard Sync
Soft Sync
As described on page 3, each VCO has
a modulation switch which can be
switched to exponential or through-zero
linear (TZFM) type of frequency
modulation. The following scope shots
show the difference. The modulating
wave (red) has been patched to the FM
input of the carrier wave (blue). Due to
its balanced nature, the fundamental
observed frequency of the carrier wave
stays relatively constant when using
TZFM. This is not true with exponential
FM.
Through-Zero Linear FM
Exponential FM
© 2022 Weston Precision Audio
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MAINTANENCE
2V2, like most modular synth equipment
will not need any particular periodic
maintenance. However, some people
may want to adjust the trimmer pots on
the module, such as perfecting the V/oct
response for your particular case, MIDI
converter, etc.. The following trimmer
pots are located on the rear PCB of 2V2
and are labeled on the top side of the
board with their function:
On the top edge of the rear PCB:
-V/oct trimmer VCO A (VOA)
-High Frequency compensation trimmer
VCO A (HFA)
-V/oct trimmer VCO B (VOB)
-High Frequency compensation trimmer
VCO B (HFB)
On the bottom edge of the rear PCB:
-Sine shape trimmer VCO A (SINA)
-Sine shape trimmer VCO B (SINB)
CONCLUSIONS
As with any piece of modular synth
equipment, it is best to just play with it
by itself and with other modules. Find
what you like and most importunely,
have fun making music!!
© 2022 Weston Precision Audio
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-12V Node

REVISION HISTORY
01: Initial release.
© 2022 Weston Precision Audio
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