4ms Company Listen Four Quarters User manual

Listen Four Quarters
4ms Company
User Manual 1.0 – Dec 31, 2018
The Listen Four Quarters is a four channel stereo mixer with 1/4” (6.35mm) TRS balanced outputs and
1/8” (3.5mm) headphones output. Two mono channels with Pan knobs and two stereo channels with dual inputs
provide optimal compatibility with both stereo and mono signals. The Listen Four Quarters can be daisy-chained
to other Listen modules to create a larger mixer with sub-mix outputs. Listen Four Quarters features include:
• Four input channels (two with stereo inputs, two with mono inputs and a Pan knob)
•Headphone and main 1/4” outputs, each with separate Level knob
• Balanced TRS outputs, switchable to stereo
• Line level output driver with zero impedance, capable of driving long cables
• Low noise, cross-talk, and bleed-through
• Anti-pop feature that silences pops and thumps when the power is turned on
•Headers in back allow for connecting to other Listen Four or Listen Four Quarters modules to create a
mixer with 8, 12, 16, or more channels and multiple sub-mix outputs
• Connects via headers to WAV Recorder module for recording final mix without using patch cables
• Signal lights for each channel and output mix
LISTEN
FOUR QUARTERS
Level 1
Pan 1
Pan 2
Level 2
Level 3
Level 4
Main
L R
L R
Balanced
Stereo
TRS

Table of Contents
Setting up your Listen Four Quarters
1. Power off your Eurorack system.
2. Connect the free end of the included power cable to a 16-pin Eurorack power header
on your power supply distribution system. The red stripe should match the white line
or -12V marking on the power distribution board. The other end of the power cable is
a 10-pin connector which should already be connected to the Listen Four Quarters
with the red stripe on the power cable orientated towards the bottom of the module.
Note: The Listen Four Quarters is reverse-polarity protected, but incorrectly
connecting any module can damage any other on the power bus.
3. Using the included screws, securely attach the Listen Four Quarters to the rails of
your case.
4. Power on your Eurorack system.
Setting up your Listen Four Quarters!2"....................................................................
Inputs!3".....................................................................................................................
Main Outputs!3".........................................................................................................
Stereo TRS/Balanced Switch!4"................................................................................
Headphones Output!4"..............................................................................................
INS Header!5"............................................................................................................
OUTS Header!5".........................................................................................................
Daisy-chaining!5".......................................................................................................
Anti-pop circuitry!7"...................................................................................................
Electrical and Mechanical Specifications!7..............................................................
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Inputs
The Listen Four Quarters has four input channels on the front. A fifth stereo channel can be
accessed through a header on the back.
Level Knobs
All four channels have a Level knob. This knob sets the volume which will appear on the
outputs. The Listen Four Quarters is very quiet, so turning the knob all the way down will
completely mute the channel (over -100dB of attenuation, typically).
Channel Signal Lights
All four channels have a signal light which gets brighter as the signal gets louder. The color of
the light indicates the stereo content: blue displays the signal on the left channel, and green
displays the signal on the right channel. The signal light shows the signal post-fader (after the
Level knob). These lights are useful for determining which channels are active at any given
moment. However, they should not be used as precision indicators. For example, the green
lights will appear dimmer than the blue lights at low audio levels and brighter than the blue
lights at louder levels.
Channels 1 and 2: Panning
Channels 1 and 2 each have one input jack and a Pan knob. These channels accept a mono
signal. Turning the Pan knob to the left or right will place the signal in the stereo field by
fading it between the left and right outputs. The Pan knob has a small detent in the center
position so you can find the center by feel.
The panning curve has been carefully designed to achieve the perception of a sound source
being a consistent distance from the listener as it pans around.
Channels 3 and 4: Stereo inputs
Channels 3 and 4 each have left and right input jacks. Patching a stereo signal into these
jacks will accurately maintain the stereo image as the signal is mixed into the outputs. If you
patch a mono signal into the left jack and nothing into the right jack, the mono signal will
appear on both left and right outputs.
Channel 5: INS header
See INS header section below
Main Outputs
Main Level Knob
The Main Level knob controls the volume of the main left and right output jacks. When knob
is turned fully to the left, the outputs are muted. Turning the knob the to right increases the
volume.
Left and Right Output Jacks
The main outputs of the module are the left and right output jacks. The signal level on these
jacks is controlled by the Main Level knob and designed to drive line-level equipment. These
jacks have a zero-impedance balanced line driver circuit capable of driving long cables. The
jacks are TRS 1/4” (6.35mm) and will output a balanced signal. Using a mono cable with
either jack will disable the balanced circuitry and a mono signal will be output. The switch
must be set to Balanced if mono cables are used, or else the right channel will be muted (see
Stereo TRS/Balanced Switch section below).
The signal will never clip because the Listen Four Quarters inputs modular-level signals
and outputs line-level signals. Thus the overall gain is less than one.
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Level 1
Level 1
Pan 1
1
Main
L R
Always flip the switch to Balanced when using mono
(TR) cables, or else the right channel will be muted.

Output Signal Lights
The two lights near the output jacks indicate the
signal level present on the main output jacks. The left
light turns a brighter blue as the left channel output
gets louder. The right light turns a brighter green as
the right channel output gets louder.
Stereo TRS/Balanced Switch
This switch selects the type of output on the main 1/4” jacks.
When the switch is flipped down to Balanced, the jacks will output a balanced signal suitable
for a TRS cable. The left and right jacks will output the left and right channels of the mix,
respectively. On the TRS cable, the signals are as follows:
Tip = + Signal, Ring = – Signal, Shield = Ground.
If a mono cable is used instead of a TRS cable, the circuitry will automatically convert to
unbalanced mode and the amplitude will be compensated so the overall volume remains the
same. If possible, use balanced signals and TRS cables, as they reduce noise substantially.
When the switch is flipped up to Stereo TRS, the left jack changes functionality in such a way
that both the left and right channels of the mix will be output on the left jack. On a TRS cable
in the left jack, the signals are as follows:
Tip = Left channel, Ring = Right channel, Shield = Ground.
If a mono cable is patched into the left jack while the switch is flipped to Stereo TRS, the
right channel will be grounded and muted. This means the right jack will no longer output
properly. Therefore, flip the switch to Balanced if you are using mono cables.
Besides this potential grounding of the right signal via a mono cable in the left jack, no
change to the right jack happens when the switch is flipped to either position: the right jack
always outputs a balanced signal.
Headphones Output
Headphones Jack
The headphones jack is a stereo 1/8” jack (3.5mm) designed for outputting to headphones.
Any headphones can be used, though 8 to 32 ohms is recommended. The jack can also be
used as an additional output to connect to an external device that requires a TRS stereo
signal. However, use the main outputs if possible because the frequency response and noise
specifications of the headphones output are not as good as the main output jacks, and this
output does not have the anti-pop circuitry.
Headphones Level Knob
This knob sets the headphones volume. It’s independent of the Main Level knob.
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Type of 1/4” Cable
Switch Setting
Jacks to Use
Balanced (TRS)
Both jacks
Mono
Both jacks
Stereo L/R (TRS)
Left jack only!
(L/R stereo signal)
!Balanced
!Stereo TRS
!Balanced
Balanced
Stereo
TRS
Note:!The signal lights only indicate
relative dynamics. Pulsing
lights often indicate beats or
throbbing sounds. It’s normal
that the blue lights are
brighter than the green lights
at softer volumes.

INS Header
A three-pin header labeled INS on the back of the Listen Four Quarters allows you to
connect another module as an auxiliary stereo input. Whatever signal is fed into the header
will appear on the outputs without any attenuation. The INS header has pins for the left
channel (bottom pin), right channel (top pin), and ground (center pin). The input impedance is
47k.
A typical use would be to daisy-chain multiple Listen modules to create a mixer with eight or
more channels. To do this, the OUTS header on one module is connected to the INS header
on the other module. See the Daisy-chaining section for details.
OUTS Header
A three-pin header labeled OUTS on the back of the module allows you to send the main
output mix to another module with a compatible header. The pin order and pin dimensions of
this header are the same as the INS header (see previous section). The output impedance is
1k. It will not damage the circuitry if the pins are shorted to ground.
The Main Level knob controls the level on the OUTS header. The main outputs and
headphones outputs are unaffected by the use of the OUTS header.
Daisy-chaining
Multiple Listen modules can be connected to form
a large mixer. For example, connecting two Listen
Four modules creates an eight channel stereo
mixer: the four inputs of the first Listen Four are
added to the four inputs of the second Listen Four
(see photo on the left).
You can daisy-chain as many modules as you
want. Connecting a Listen Four Quarters after
the two Listen Fours in the example above will
create a 12 channel mixer with 1/4” balanced
outputs, and two sub-mix outputs.
You can also connect a WAV Recorder module to
the end of a chain of Listen modules, allowing you
to record the main outputs without using patch
cables.
How to Daisy-chain
To daisy-chain two modules, use a 3-pin cable to connect the OUTS header of one module to the INS header of
another. You can continue to connect more modules in the same way, OUTS to INS.
A suitable connecting cable can be purchased from 4ms Company or many of our dealers. You also can find or
create your own cable. The cable must fit a single row of three pins with a pin spacing of 0.1” (2.54mm). The pins
are 0.2” tall (5mm), which is the same spacing, size and length as the pins on standard Eurorack power headers.
Make sure the same color wire is on top on both sides of the connecting cable. If one side is reversed, the left and
right channels will be reversed (though no damage or malfunction will occur).
Main Mixes and Sub-mixes
The Main Level knob controls the level that’s passed to the next Listen module via the OUTS header. By
patching related signals into the same Listen module, you can create sub-mixes with a single knob for level
control.
For example, see the photo above. Two Listen Four modules are connected such that one module’s OUTS
header connects to the other module’s INS header. Let’s say you patch some polyrhythmic drum sounds into the
first Listen Four, and patch some processed field recordings into the second Listen Four. The output jacks on
the second Listen Four will be a mix of everything (the drums and field recordings), and the Main Level knob will
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control the overall level. The output jacks on the first Listen Four will be a sub-mix of just the drums, and its Main
Level knob will control just the level of the drums in both the sub-mix and the overall mix.
Connecting to the WAV Recorder
The WAV Recorder just has an INS header, and so it can only be connected at the end of a daisy-chain. This is
useful for making a recording of the main mix. Since the WAV Recorder can accept line or modular level signals,
the Listen Four’s switch can be set to either Line or Mod. The Input Gain knob on the WAV Recorder can be
adjusted to the maximum recording level without clipping. Adjusting this knob will not effect the output level of the
Listen modules.
In the photo above, two Listen Fours and a WAV Recorder are daisy-chained by connecting the OUTS to INS
headers. This creates an eight channel mixer with a stereo recording of the main mix.
The photo on the right shows a
twelve channel mixer with stereo
recording of the main mix.
Patching into any of the twelve
channels will pass the signal to
the 1/4” outputs, as well as the
WAV Recorder. No cables
need to be patched between
modules. Each Listen module’s
Main Level knob controls the
sub-mix level of its four channels
plus the module to the left of it.
The sub-mix can be taken simply
by patching into the Left and
Right output jacks on the Listen
Four modules. The headphone
jack on these modules can also
be used to cue or monitor the
sub-mix.
"
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Twelve channel mixer with two four-channel sub-mixes, 1/4” balanced stereo
outputs and stereo recording directly from the main mix. Each sub-mix has a
headphone jack with independent level for cueing.

Anti-pop circuitry
The Listen Four Quarters has a special feature that prevents the main outputs from popping or thumping when
the power is turned on. This avoids a common problem that happens when the power is accidentally turned off
and back on again while connected to a PA or powered speaker system, or the power is turned on after the
speakers are turned on. When using most mixers, the result is a loud pop that can damage the speakers (and
frighten anyone nearby!). The Listen Four Quarters automatically mutes the outputs during power-on, thus
avoiding any pops.
Electrical and Mechanical Specifications
• 12HP Eurorack format module
• 1.13” (28.7mm) maximum depth (includes power cable)
• 10-pin Eurorack power header
•Power consumption
•Maximum values without using headphones jack:!
Main outputs shorted to ground, headphones jack not used, maximum signal levels on all channels
•+12V: 107mA
•-12V: 101mA
•Maximum values in worst-case conditions:!
All outputs including headphone jack shorted to ground, maximum signal levels on all channels
•+12V: 290mA
•-12V: 101mA
• Main outputs
•Output type: balanced zero-impedance, compensated for electrolytic capacitor distortion
•Frequency Response: +/-0.2dB max deviation, 10Hz - 20kHz
•Maximum output level: 17.1V peak-to-peak (+17.8dBu)
•Maximum gain of channels 1 and 2: -4.4dB (hard-panned), -9.1dB (center-panned)
•Maximum gain of channels 3 and 4, and INS header: -7.5dB
•Channel bleed-through (Main Level attenuation):
Test conditions: Test signal input into each channel with Level knob at 100%. Frequencies from
20Hz to 20kHz tested. Result given as a ratio of the signal measured on main output jacks with
Main Level knob at 0%, to the signal measured with Main Level knob at 100%. Worst-case results
for any channel and frequency reported.
•Output jack tip: <-110dB
•Channel bleed-through (channel attenuation):
Test conditions: Test signal input into each channel with Level knob at 0% and Main Level knob at
100%. Frequencies from 20Hz to 20kHz tested. Result given as a ratio of the signal measured on
main output jacks with channel Level knob at 0%, to the signal measured with channel Level knob
at 100%. Worst-case results for any channel and frequency reported.
•Output jack tip: -106dB
•Channel cross-talk:
Test conditions: Test signal input into each channel. Level knob at 0%, and other channel Level
knobs at 100%. Main Level knob at 100%. Frequencies from 20Hz to 20kHz tested. Measured
signal subtracted from signal with all Level knobs at 0%, and result given in dB as a ratio to output
signal with test channels’ Level knob at 100%. Worst-case results for any channel and frequency
reported.
•Output jack tip: <-110dB
•Headphones jack
•Frequency response: -0.2dB at 20Hz; 0dB at 100Hz to 20kHz (driving 32Ωheadphones)
•Maximum voltage (peak-to-peak): 5Vpp
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