Source audio Gemini Chorus User Manual
Gemini Chorus User’s Guide
Welcome
Thank you for purchasing the Gemini Chorus. This powerful stereo effects pedal features a collection
of meticulously crafted chorus sounds ranging from classic dual-voice sounds to lush quad-voice
ensembles. With a simple control set, the Gemini can work in a wide variety of musical settings, and
the powerful MIDI and Neuro control options under the hood provide access to a vast array of
additional tonal possibilities.
The Gemini is housed in a durable, lightweight aluminum housing, packing rack mount power and
flexibility into a compact, easy-to-use stompbox.
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The USB and Neuro ports transform the Gemini from a simple chorus pedal into a powerful multieffects unit. Using the free Neuro App (iOS and Android), a wide range of additional control
parameters and effect types (phaser, flanger, resonator) are accessible. When used together with the
Neuro Hub, the Gemini is fully MIDI-controllable and 128 multi-pedal presets, or “scenes,” can be
saved for instant recall on the stage or in the studio. The Gemini can also connect directly to a
passive expression pedal or the Hot Hand for expressive control of any parameter.
The Quick Start guide will help you with the basics. For more in-depth information about the Gemini
Chorus, move on to the following sections, starting with Connections.
Enjoy!
- The Source Audio Team
Overview
Diverse Chorus Sounds – Choose from traditional chorus tones such as Dual, Classic, and Quad, or
delve deeper into unique sounds cooked up in the Source Audio lab.
Flexible Stereo Routing – The Gemini is equally at home in a mono rig or a stereo rig. A variety of
routing modes such as True Stereo, Mono, Mono-to-Stereo, Sum-to-Mono and External Loop allow
the Gemini to harness the true power of stereo signal chains.
Compact Design – The durable, anodized aluminum housing has a slim profile, a small footprint, and
sturdy hardware that will withstand the rigors of the road.
Universal BypassTM – True bypass or buffered bypass? The choice is yours. The Gemini features high-
quality signal relays for true bypass and transparent buffers for analog bypass.
Preset Saving – Save your favorite sound by pressing and holding the footswitch. No need to
remember knob positions in the middle of a show.
Neuro Technology – The Neuro App opens up new possibilities for the Gemini, including completely
new effect types, additional control parameters, and access to the Neuro Community, including free
presets from artists and other users. The Neuro Hub can store up to 128 presets for the Gemini,
easily recalled with a MIDI controller. You can also download any effects for the Lunar Phaser or
Mercury Flanger and use them on the Gemini Chorus.
Deep Control Set – Beyond the four knobs on the face of the Gemini are many additional parameters.
The Neuro App provides access to the inner workings of the chorus effect for advanced users who
want to create a unique signature sound.
Parametric EQ and Low Cut – A 4-band parametric EQ is included in the Gemini, allowing for fine
tonal control, and a low cut filter tightens up the low end.
MIDI Control – All of the Gemini’s parameters can be accessed and controlled using MIDI via the
Neuro Hub or USB. Class compliant USB-MIDI allows the Gemini to work as a plug-and-play device
with recording software running on Mac and Windows, and the MIDI Learn feature makes control
mapping simple. The Gemini can also sync to your DAW or other MIDI devices using MIDI clock.
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Quick Start
Power
To power the unit, connect the included 9V DC power supply to the jack labeled DC 9V on the back
panel.
Warning: Using a non-Source Audio supply, especially an unregulated supply, could damage the unit.
Please be very cautious when using 3rd-party power supplies.
Guitar/Audio Connections
Using standard ¼” mono cables, connect your guitar, bass, or other instrument to the INPUT 1 jack
and your amp (or the next audio device in the signal chain) to the OUTPUT 1 jack.
When the power and audio connections have been made, the Gemini is ready to play.
Brief Knob, Footswitch, and Button Descriptions
Depth Knob: Controls the depth of the Low Frequency Oscillator (LFO), which determines the
strength or prominence of the chorus effect.
Speed Knob: Controls the frequency of the LFO, which determines the speed of the chorus effect.
Mix Knob: Sets the relative levels on the dry (clean input) signal and the wet effects signal, allowing
you to dial in just the right amount of chorus.
Tone Knob: Controls the tonal balance of the output, making either the treble or bass more
prominent.
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Effect Switch: Selects between the three basic chorus effect types – Dual, Classic, and Quad.
Footswitch: Enables or bypasses the chorus effect. The large LED will be lit green when the chorus
effect is engaged.
Contents
Welcome .................................................................................................................................................. 1
Overview .................................................................................................................................................. 2
Quick Start ............................................................................................................................................... 3
Connections ............................................................................................................................................. 5
Basic Chorus Operation ........................................................................................................................... 9
Effect Types ............................................................................................................................................ 11
Controls .................................................................................................................................................. 12
Preset Storage and Recall ...................................................................................................................... 14
Universal Bypass TM ................................................................................................................................ 14
Stereo Routing ....................................................................................................................................... 15
Parametric EQ ........................................................................................................................................ 16
External Control ..................................................................................................................................... 17
Neuro App .............................................................................................................................................. 20
Specifications ......................................................................................................................................... 30
Troubleshooting ..................................................................................................................................... 31
Frequently Asked Questions .................................................................................................................. 32
Rubber Feet ........................................................................................................................................... 34
Waste Disposal Notes ............................................................................................................................ 34
Warranty ................................................................................................................................................ 35
Version History ...................................................................................................................................... 36
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Connections
Input Side Connections
Input 1
This is the primary input for guitar, bass, or other instruments. It can also accept line-level inputs.
Connect it to your instrument or other audio source using a mono (TS) ¼” cable.
Input 2
Input 2 can act either as an audio input or as the data connection for the Neuro App, or both at the
same time.
Input 2 as an Audio Input
The tip contact on Input 2 acts as a secondary input for guitar, bass, or other instruments. It is only
active when the Gemini is configured with a signal routing that uses stereo inputs. Connect it to your
instrument (or the previous effect in the signal chain) using a mono (TS) ¼” cable. By default, the
Gemini will auto-detect the routing mode. Other routing options are available using the Neuro App.
For more information about stereo routing, refer to the Stereo Routing section.
Input 2 as a Neuro App Data Input
The ring contact on Input 2 acts as a data connection for the Neuro App. Connect it to your mobile
device using a stereo (TRS) ¼” cable. It can also accept daisy-chained Neuro data from another
Neuro-compatible pedal in the chain, provided that a TRS cable is used. The audio signal (if
applicable) will be on the tip contact of the plug, and the Neuro App data will be on the ring contact.
Input 2 only accepts data from the Neuro App. Data from the Neuro Hub comes from the Control
Input port.
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Output Side Connections
Output 1
This is the primary output. Connect it to your amplifier, recording interface, or the next device in
your effects signal chain using a mono (TS) ¼” cable.
Output 2
Output 2 can act either as an audio output or as the daisy-chain data connection for the Neuro App,
or both.
Output 2 as an Audio Output
The tip contact on Output 2 acts as the secondary audio output. It carries an audio signal when the
Gemini is configured with a signal routing that uses stereo outputs. Connect it to your amplifier,
recording interface, or the next device in your effects signal chain using a mono (TS) ¼” cable.
Output 2 as a Neuro App Data Daisy-Chain Output
The ring contact on Output 2 acts as a data connection for the Neuro App, passing data from the
Gemini to the next Source Audio effect in your signal chain. You can daisy-chain the Neuro App data
regardless of whether Output 2 is configured to output audio or not. Connect Output 2 to the next
device’s Neuro App Data input (usually Input 2) using a stereo (TRS) ¼” cable. The audio signal (if
applicable) will be on the tip contact of the plug, and the Neuro App data will be on the ring contact.
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Guitar In
Neuro In
Out to Amp
Neuro
Daisy-Chain
Guitar In
Neuro In
Out to Amp (Left)
Audio (Right)
and
Neuro Daisy-Chain
Out to Amp (Right)
Audio (Left)
Example Neuro Daisy-Chain Connections
Mono Audio Path with Neuro Daisy-Chain
In the case of a purely mono audio signal path, the Neuro data can be input to the first effect directly
from the mobile device and then carried on to the second effect via TRS cable.
Mono-To-Stereo Audio Path with Neuro Daisy-Chain
In the case of a signal path that splits a mono input to stereo outputs, the Neuro data can be input to
the first effect directly from the mobile device and then carried on to the second effect via TRS cable.
The audio signal is carried on the same cable.
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Power and Control Connections
DC 9V (Power)
Connect to the included 9 Volt DC power supply. The power supply must be regulated at 9 Volts
(direct current), able to source at least 180 mA (milliamps) of current, and the plug should have a tipnegative, sleeve-positive polarity (the center tip is ground and the sleeve is power).
USB
Connect to your computer (Mac or Windows) to the Gemini’s USB port (denoted by the icon)
using a standard mini USB cable. The Gemini is a class compliant USB device, meaning that it should
be recognized by Mac and Windows computers automatically. For more information about the
Gemini’s USB capabilities, refer to the USB section of the User’s Guide.
Control Input
The 3.5 mm Control Input port connects to external control devices such as the Dual Expression
Pedal, Reflex Universal Expression Pedal, Neuro Hub, and Hot Hand Motion Controller. For more
information, refer to the Expression Pedal Input, Hot Hand Input, and Neuro Hub sections of the
User’s Guide.
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DELAY TIME
TIME
Basic Chorus Operation
When multiple musicians perform the same music in unison, their performances will always differ in
small ways – each individual musician’s timing, pitch, and intensity will not exactly match the other
musicians, creating an overall sound that can be subjectively fuller or deeper than that of a single
musician. This result is commonly called chorusing.
The chorus effect attempts to recreate the sounds of multiple musicians playing in unison with only a
single instrument as an input. For example, a chorused guitar should, ideally, take one guitar and
make it sound like several guitars playing the same thing at the same time.
This effect is accomplished by creating copies of the input signal that differ slightly in timing, pitch,
amplitude, and (when in stereo mode) location in the stereo field.
As far as audio effects go, the chorus effect is very old. As early as the 1940s, analog delay circuits
with very short delay times were used in the Hammond organ to create a primitive chorus sound.
The Gemini uses multi-tap digital delay lines with modulated timing, amplitude modulation, panning,
and a few other tricks and techniques to create its wide array of chorus sounds.
The amount of delay in the chorus effect needs to be changed over time to create a convincing
representation of multiple voices. In order to do this, a low frequency oscillator (also known as an
LFO) is used to control the delay time, as well as several other parameters. This is illustrated by the
following graph:
The blue line in the graph is known as the LFO. It changes the amount of delay over time.
The frequency (a.k.a. “rate” or “speed”) of the LFO can be increased to get a more rapid change in
the delay time, as shown in this graph:
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DELAY TIME
TIME
DELAY TIME
TIME
OUTPUT GAIN
TIME
The depth of the LFO can also be changed to make the chorus effect more or less prominent, as
shown in this graph:
Finally, the shape of the LFO can be changed to give the chorus effect a different character.
Sine wave:
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OUTPUT GAIN
TIME
Square wave:
By default, the Gemini uses a sine wave for its LFO, but other wave shapes can be selected using the
Neuro App.
Effect Types
The Gemini includes three basic effect types, with more effects available in the Neuro mobile app.
Classic
The Classic Chorus effect combines the original dry input signal with a single modulating clone signal,
creating the simple sound of two voices in unison. It is very similar to the classic flanger effect except
that the delay time is relatively long in a chorus effect and relatively short in a flanger effect.
Dual
The Dual Chorus effect is a dual-voiced chorus that produces a more animated chorus effect than the
single-voiced Classic Chorus.
Quad
The Quad Chorus effect combines the dry input signal with four additional voices that modulate in
different ways, creating a deep and lavish chorus sound that was in heavy use in the late 80s.
Additional Effect Types
Additional effect types can be loaded into the Gemini using the Neuro App on your mobile device
(iOS and Android).
The Gemini Chorus is compatible with Source Audio’s Phaser and Flanger effects, so it is possible to
load chorus, phaser, and flanger effects on the Gemini at the same time.
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