Grimm UC1 User manual

Please read this manual before operating the
unit.
Mixing and mastering requires a point of reference.
A modern workow demands for a tailored setup.
UC1: the swiss army knife of high quality monitoring.
Please read this manual before operating the unit.

Manual UC1 © Grimm Audio
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Table of Contents
1. Introduction 3
2. Important Safety Instructions 5
3. Installing 7
4. Signal Connections 9
5. Operation 14
6. Menus 26
7. Specications 33
8. Grimm Audio Limited Warranty 34
Table of Contents

Manual UC1 © Grimm Audio 3
1. Introduction
The UC1 “Universal Converter” combines an 18 I/O
channel USB interface with a versatile monitor
controller. It oers broad functionality for mixing and
mastering at very high audio quality level, in a compact
box. Please read this manual before using the UC1 to
understand its operation and make optimal use of its
versatility.
Applications
The number of application examples for the UC1 is
endless. Its main intended use however is to function as
the center piece of a modern mixing or mastering setup
in a professional audio studio. Let’s have a look at how
to use the various inputs and outputs in this context.
The back USB is connected to your DAW computer. A
main monitor loudspeaker can be connected to one of
three options: the digital RJ45 Grimm LS1 / PMC 1
connector, an analog XLR pair, or the digital AES3 XLR
output. In the menu you select to which output your
main monitor is connected. A secondary smaller
loudspeaker system can be connected to a dedicated
XLR output pair that runs in parallel to the headphone
output on the front that oers a third monitor option.
Several monitor tools such as mono, side and stereo
swap are available.
Next to the monitor paths, the UC1 oers a stereo
analog and a stereo digital eect loop. Through these,
outboard gear can be used in your DAW project. Audio
levels can be monitored on a special meter display with
high res peak meters.
Furthermore the UC1 oers inputs that can be used for
recording into your DAW or just for monitoring. These
are a second stereo digital input on the back, a stereo
analog jack input on the front and a second USB input
on the front, called ‘i-put’. The stereo jack input has high
input impedance, so it is equally well suited for
1. Introduction
1The UC1 needs to reboot in PMC mode to send the right
instructions to your digital PMC loudspeaker. Please read
chapter 4 Signal Connections, under “On the back” for
instructions about how to boot the UC1 in PMC mode.

Manual UC1 © Grimm Audio
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recording a stereo MP3 player as DI instrument
recording.
The UC1 oers a ‘Foldback’ function on a few inputs,
which means it can oer latency free monitoring of
these inputs on headphones, mixed with the selected
main audio source (for instance from the back USB). A
polarity switch makes sure your headphones are in
phase with your acoustic sound in case you’re using a
microphone.
Most people will use the UC1 as a USB interface. It is
however also possible to use the UC1 as a standalone
converter and monitor controller, without computer
connection. In this case the clock settings need to be
changed in the UC1 menu. When using the UC1 with the
back USB connector, the computer OS controls all clock
options and the clock menu of the UC1 is greyed out.
Last but not least the UC1 oers a BNC word clock input
and output to synchronize the UC1 with other
converters in your setup. The clock quality equals that
of Grimm Audio’s CC1 and CC2 master clocks.
1. Introduction

Manual UC1 © Grimm Audio 5
2. Important Safety Instructions
Grimm Audio gaat er van uit dat u deze Engelstalige tekst
volledig begrijpt. Als u hier moeite mee heeft dient u contact
op te nemen met Grimm Audio. Op verzoek sturen wij u een
vertaling toe.
Grimm Audio nimmt an, dass Sie diesen Englischen Text
völlig verstehen. Wenn notwendig, nehmen Sie bitte Kontakt
auf mit Grimm Audio. Auf Wünsch wird Ihnen eine
Übersetzung zugeschickt.
Grimm Audio suppose que le lecteur comprend
parfaitement le texte en Anglais ci-dessous. En cas de doute
s.v.p. contacter Grimm Audio. Si necessaire, on pourra vous
envoyer une traduction.
Grimm Audio da por supuesto que el texto en versión
Inglesa no ofrece ninguna duda de interpretación y se
entiende integramente. Si este no fuese su caso rogamos
contacte con Grimm Audio quien, a petición, se encargaría
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Please follow these precautions when using
this product:
1. Read these instructions.
2. Keep these instructions.
3. Heed all warnings.
4. Follow all instructions.
5. Dangerous voltage is inside this apparatus. Opening
is only allowed by qualied service personnel.
6. Do not defeat the safety purpose of the polarized or
grounding-type plug. A polarized plug has two
blades with one wider than the other. A grounding-
type plug has two blades and a third grounding
prong. The wide blade or the third prong are
provided for your safety. When the provided plug
does not t into your outlet, consult an electrician
for replacement of the obsolete outlet.
2. Important Safety Instructions

Manual UC1 © Grimm Audio
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7. Protect the power cord from being walked on or
pinched, particularly at plugs, convenience
receptacles, and the point where they exit from the
apparatus.
8. Unplug this apparatus during lightning storms or
when unused for long periods of time.
9. Do not use this apparatus near water.
10. Do not use this apparatus outside.
11. Do not expose the apparatus to dripping or
splashing. Do not place objects lled with liquids
(ower vases, drink cans, coee cups, etc) on the
apparatus.
12. Clean only with a dry, soft, non-uy cloth. Do not
spray any liquid cleaner onto the cabinet, as this
may lead to dangerous shocks. Do not spray any
liquid cleaner onto the faceplate, as this may
damage the wooden front panel.
13. Install in accordance with the manufacturer’s
instructions.
14. Do not install near any heat sources such as
radiators, heat registers, stoves, or other apparatus
(including ampliers) that produce heat. Avoid
exposure to direct sunlight.
15. Use only attachments or accessories specied by
the manufacturer.
16. Use only with a cart, stand, bracket, or table
designed for use with professional audio or music
equipment. In any installation, make sure that
injury or damage will not result from cables pulling
on the apparatus and its mounting. If a cart is used,
use precaution when moving the cart/apparatus
combination to avoid injury from tip-over.
17. This apparatus typically runs warm when operated.
Install in a normal ventilated area. If the product will
be used in a rack, make certain there is sucient air
movement within the rack. Preferably oer some
2. Important Safety Instructions

Manual UC1 © Grimm Audio 7
empty rack space above the unit and do not place it
on top of hot equipment.
18. Refer all servicing to qualied service personnel.
Servicing is required when the apparatus has been
damaged in any way, such as when the power-
supply cord or plug is damaged, liquid has been
spilled or objects have fallen into the apparatus, the
apparatus has been exposed to rain or moisture,
does not operate normally, or has been dropped.
19. WARNING: To reduce the risk of re or electric
shock, do not expose this apparatus to rain or
moisture.
3. Installing
Unpacking and Inspection
Your UC1 was carefully packed at the factory and the
packaging it came in was designed to protect it from the
trials and tribulations of shipping. Keep the box and all
packing materials, so that in the unlikely event that you
need to return the UC1 for servicing, you can do so
safely.
AC Power Hookup
The UC1 has a ‘full mains’ switch mode power supply
that works with all choices of mains voltage world wide.
This SMPS is developed by Grimm Audio and oers the
highest possible sound quality. For your safety and for
optimal sound quality, always use a power outlet with
proper safety earth.
The UC1 is shipped with a mains cable. Grimm Audio
cannot be held responsible for problems caused by
using the UC1 with improper AC wiring.
3. Installing

Manual UC1 © Grimm Audio
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3. Installing
The UC1 does not have a power switch on the front
panel, it needs to be powered down with the mains
switch at the back. A convenient way to power down the
unit is to use a power strip equipped with a switch, or a
power sequencer.
The high sound quality DC coupling of the UC1’s analog
outputs may result in a popping sound when turning o
the unit while the downstream monitor system is still
turned on. We recommend to use a manual or
automatic power up and power down sequence as
follows: rst turn the UC1 on and then the monitors.
And at the end of your working day, rst turn o the
monitors and then the UC1.
Mounting the UC1
Since high quality audio electronics draw above average
current, the UC1 runs warm. Note that the bottom plate
is used as a heat sink, there is no active cooling. Please
allow for sucient air movement around the unit.
The UC1 does not produce strong RF elds nor is
susceptible to them. You can position it near other
digital gear such as computers and disk recorders
without worry. In general it is a good idea to keep some
distance between monitors (LCD and CRT) and audio
cables because of risk of induced low level noise due to
stray magnetic elds.
Grimm Audio products have a real wooden face plate
that provides a beautiful and vivid appearance. The UC1
front panel is made of Padauk. The panel is nished
with an environmentally friendly oil. To maintain the
outstanding looks, one is advised to take some
precautions:
• Use a dry woolen cloth to clean the wood.
• Do not place the UC1 in very dry environments.
• Do not use chemical or alcohol based cleaner on
the wood.
• Avoid exposure to direct sun light, since the padauk
wood is susceptible to discolor in UV light.

Manual UC1 © Grimm Audio 9
4. Signal Connections
Remote
control
(future use)
Digital
inputs Main USB Word clock I/O 2nd speaker outputs Analog (loop) outputs Analog main outputs Analog (loop) inputs
Digital
outputs
Control
buttons Main dial
Hi-Z stereo jack
input and gain 2nd (stereo) USB input
4. Signal Connections
08-0.002.xxx
Mains power
connection
Phones output
and gain

Manual UC1 © Grimm Audio
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On the back
The USB connector on the back oers a USB Audio Class
2 compliant interface. It is natively supported by Mac
OS, Linux and Windows 10. For Windows 7 and Windows
8 we oer a driver that can be downloaded from the
downloads section of the UC1 page of our website
grimmaudio.com. Note that it is recommended to install
this driver on Windows 10 too.
The UC1 can also be operated without USB, as a high
quality multi-input DAC. In that case the clock source
needs to be selected in the UC1 menu in stead of the
computer OS. Please refer to the menu chapter,
paragraph ‘F2’, for instructions.
All analog inputs and outputs on the back of the UC1
are XLR’s. Our design aim was to avoid sub-D
connectors since they are not of the same quality as
XLR’s. The nominal output voltage of all analog
connections is +4 dBu. This is aligned to -14 dBFS, hence
the clip level is at +18 dBu. These are common levels in
mastering studios. The analog inputs on the back can
optionally be switched to a clip level of +24 dBu so one
can drive vintage outboard gear to the max without
clipping the UC1 input that receives their signal. Of
course the 1:1 relation between output and input level
of the UC1 is then lost.
The digital inputs and outputs are in AES3 format.
Leftmost is the “LS1 control out’ cat5 connector. This is
not ethernet but a proprietary combination of AES3 and
midi control data. We share this type of connector with
our friends of PMC. If you own a digital PMC
loudspeaker such as the TwoTwo, IB2S or QB1 series,
the UC1 can be setup to send the right control data and
control its volume and mute function. To do this, please
follow these instructions:
Boot the UC1 as PMC loudspeaker controller
Directly after turning on the UC1 a progress bar startup
display can be seen on the UC1 screen. While this bar is
visible, rst press the top button, hold it and then press the
bottom button. Release when the bar is gone. Your UC1 is
now in ‘PMC mode’. In case you like to return to ‘Grimm LS1’
4. Signal Connections

Manual UC1 © Grimm Audio 11
mode, reset the unit to factory default by only pressing the
top button during startup.
The word clock in- and outputs are 75 Ohm terminated.
The UC1 clock circuitry is of similar reference quality as
that of our CC1 and CC2 master clocks.
If you use more than one audio interface with your
computer, we recommend to make the UC1 master and
slave the extra devices via word clock. Make sure all
interfaces are properly synchronized, otherwise glitches
occur. To use multiple interfaces in Macintosh
computers you need to make an “Aggregate Device” in
the ‘Audio Midi Setup’ app, which combines the inputs
and outputs of all devices. For more information read
https://support.apple.com/en-us/HT202000. In Windows
systems it is more complicated. ASIO does not support
aggregated devices unfortunately. The workaround is to
use the ASIO4ALL driver that can combine USB Audio
Class 2 devices such as the UC1 and present them as
one ASIO device. For more information visit https://
www.asio4all.org.
The UC1 can slave to word clock, Digital in 1 and Digital
in 2. This enables you to monitor and record digital
sources that cannot be slaved to the UC1 word clock
output such as CD players or digital guitar modellers.
Mark that S/PDIF sources can be connected via an
S/PDIF to AES adapter cable (that can be found in the
Grimm Audio webshop).
The PLL that synchronizes the UC1’s internal clock to the
external clock is of a very special kind. It achieves lock
very fast and then gradually increases its jitter
suppression down to very low jitter frequencies,
eectively only following very slow drift of the source
clock. This proprietary ‘Hybrid PLL’ technology oers the
best of both worlds: instant lock so there is no gap when
switching sample rates, and high jitter suppression as
well. Standard PLL’s will either lock fast or oer high
jitter suppression.
The UC1 has two digital stereo inputs. Please note that
your DAW can only record data from these sources if
they are synchronous with the UC1 clock. To achieve
this, you can slave the UC1 system to digital input 1 or 2,
4. Signal Connections

Manual UC1 © Grimm Audio
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but not to both at the same time. If you like to record
from both inputs simultaneously, please make sure that
all devices that are not used as clock source are
synchronized by means of the UC1 word clock or AES
outputs.
The remote control 3.5 mm jack socket on the far right
is for future use and not yet enabled.
On the front
A unique feature of the UC1 is its front USB input, the ‘i-
put’. It is intended to connect a secondary stereo USB
source such as a laptop or smart device to the UC1 and
your DAW. Smart devices are often connected wireless
to a computer. The advantage in using the i-put with a
smart device is that in contrast with wireless
connections all sample rates and bit depths are
supported and data is transferred bit transparent. It
may also oer you a more reliable connection.
To use the USB front i-put, please note these two
important instructions:
1. The UC1 sample rate cannot be controlled from the
front USB. As a result the UC1 can only play audio from
the front USB input if the playback sample rate of the
device is the same as the current UC1 sample rate. In
case the device playback sample rate does not match
the UC1 sample rate, the i-put meters in the main and
secondary displays are red lined and the sound is
muted.
2. If you like to connect an Apple smart device such as
an iPhone or iPad, a special conversion cable called
“Lightning to USB3 camera adapter cable” or “USB-C to
USB adapter cable” (depending on your device) is
needed. These cables carry a chip that enables audio
playback to USB from iOS devices. Some cables also
provide a means to power the iDevice externally.
For the rest, the front USB behaves like that on the back:
on Mac OS, Linux, Windows 10, iOS and Android you do
not need a driver.
The front analog input is a stereo unbalanced 6.3mm
jack with a gain control next to it. It can be used for
4. Signal Connections

Manual UC1 © Grimm Audio 13
instance when someone brings in an analog MP3 player
with a reference track. This input has a high input
impedance of 1 MOhm so it doubles as an instrument
input to for instance dub a guitar or bass line in your
mix. The monitor system of the UC1 can be set to
audition this single channel input mono on both
channels.
Leftmost on the front is a 6.3mm headphone output
with gain control. The acoustic sensitivity of headphones
on the market varies by as much as 30 dB. Consumer
ear buds are more or less standardised on a sensitivity
of approximately -14 dBu for 100 dBA. Some
professional 600 Ohm headphones however may need
as much as 15 dBu to reach 100 dBA. The UC1 is
targeted at the professional audio market and therefore
oers enough gain to drive these headphones.
Please be aware that with sensitive headphones the
UC1 can produce sound pressure levels that can cause
immediate and serious hearing damage! Grimm Audio
does not take any liability to hearing loss when using
the UC1. Please act responsibly and protect yourself!
Figure 1 shows a typical application example of the UC1.
The DAW runs on the Computer on the left, but audio
can also be played from the Laptop to the second USB
‘i-put’. A Bass guitar is connected directly to the front
jack, a Guitar via a Digital Emulator to a digital input on
the back. The Emulator is synchronised via word clock,
which also improves its sound quality. There’s an Analog
and Digital eects loop. Monitoring can be done on Main
and 2nd speakers and Headphones.
Computer
Laptop
Digital Emulator
Bass
(clock)
Guitar
Analog FX Digital FX 2nd speakers
Main speakers
Headphones
4. Signal Connections
Figure 1 UC1 application example.

Manual UC1 © Grimm Audio
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5. Operation
The UC1 functions are controlled with the main dial on
the right in combination with the two small push
buttons next to it. But before we look at that in more
detail, let’s rst walk through the internal routing of the
device.
Routing
Figure 2 shows the routing diagram of the UC1. All 10
inputs are routed to their respective USB channels
transparently without any form of processing. Similarly
all 8 USB channels from the DAW ow unaltered to the
outputs on the UC1 - except for the 2 USB channels that
are associated with the main output. Mark that one can
still audition the USB sources for that pair, but only via
the monitor path that’s described in the next paragraph.
We recommend to assign these USB channels to the
master channels of your mixing desk.
The yellow blocks in gure 2 show the monitor path of
the UC1. All 18 I/O channels can be routed to this
monitor path. They can be auditioned in their original
stereo form, or in mono (L+R), side (L-R) or in swapped
channel order form. They then receive digital volume
control & mute (both channels or L or R mute).
‘Hidden functions’ of the UC1
• Press the main dial briey to mute the main
speakers and turn on the headphone output. Press
briey again to return to the main speakers.
• Press-hold the main dial until the indicated source
starts blinking. Then turn to change the monitored
source. Release to select. Alternatively, release the
dial when the blinking starts. Then turn to change
source. Press briey to select.
• Press-hold the top control button to enter the
metering display. Press-hold again to exit.
• Press-hold the bottom control button to exit or
enter Foldback mode, when enabled via the menu.
• Check chapter 4 Signal Connections, “On the back”
for instructions about how to set the cat5 output
to PMC digital monitor control or reset the UC1 to
factory default settings.
5. Operation

Manual UC1 © Grimm Audio 15
Routing
Stereo / mono
Mix
Volume, mute
and polarity
USB (back) In
Special (mono/
side/swap)
Volume and mute
Phones & 2nd out
Main out
Out LS 1/2, Ana
1/2, Dig 1/2
(when not Main)
Out Ana 3/4
Inputs
USB (back) Out
Foldback
USB 1-8
Monitor
USB 1-6
USB 7/8
10 channels
5. Operation
Figure 2 UC1 internal routing.

Manual UC1 © Grimm Audio
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In a parallel path two other channels can be selected for
‘foldback’ and mixed with the selected main source. This
is most helpful when recording a live instrument or
vocals and the latency through the computer OS
hampers your performance. The foldback can only be
heard on the phones and 2nd speaker output, to avoid
possible high SPL feedback. For foldback, the back
analog (1&2), front analog (3&4) and back digital (1&2)
inputs are available, both in stereo and mono.
The foldback mix is static. To change the balance, please
use the faders of your DAW to align the reference
channel levels with that of the recording channels. After
the mixer block, the monitor gain and mute of the
headphones and 2nd speaker output are controlled,
plus the polarity of the phones.
In case the UC1 is used without computer connected to
the back USB, some physical in- and outputs have a
xed routing. Analog in 1&2 is routed to digital out 1&2
and digital in 3&4 is routed to analog out 3&4. The main
out and monitor path selections remain functional for
all inputs.
Buttons and display
Most functions of the UC1 are adjusted via the main dial
and the two control buttons on its left side. Additionally
there are knobs for the phones output gain and the jack
input gain.
The main dial can be turned and pushed. In normal
operation, turning changes the gain of all monitor paths
(main, 2nd and phones) and pushing mutes the
speakers while engaging the headphones output on the
front. When press-holding the main dial, the current
monitor source (indicated top left of the display) starts
5. Operation
Main screen, USB 1/2 selected

Manual UC1 © Grimm Audio 17
blinking. Keep pressing the main dial while turning it to
change the monitor source. All inputs and outputs can
be selected. Their name is shown in the display and
their channels are highlighted in the meter. When
releasing the dial the indicated source stays selected.
Alternatively, release the dial when the blinking starts.
Then turn to select a source and press to conrm.
The large number in the display indicates the current
monitor gain level in dB’s. The monitor outputs oer 8
dB of clean gain above ‘0’ on the display. In other words:
a full scale signal will only reach full scale on a monitor
output if the monitor gain is set to +8 dB. This may
seem odd, but the idea is that the ‘0’ indication of the
display is your reference playback level to which you
always return after a louder of softer playback. This is
common practice in mastering. The ‘0’ level is usually
aligned with an SPL of 79dBC when playing a SMPTE
reference noise signal on a single channel. The Grimm
LS1 is factory aligned to that, you may adust the gain of
your 3rd party amplier to achieve the same result - or
to select another acoustic SPL that suits you as
reference playback level. In case you feel the need to
adjust the ‘0’ level of the UC1, you can change it in menu
P2 (see chapter 6. Menus).
Note that the monitor gain can be set to display values
up to +18, which means that there is 10 dB of positive
gain available in the UC1 to audition very soft noises.
Note that any signal above -10 dBFS will in that case clip
– please use this extra gain with caution!
The volume control is in 0.5 dB steps above -17 dB and
1 dB below it. If you have a Grimm Audio LS1 or PMC
digitally controlled loudspeaker connected to the
proprietary cat 5 output on the back, the volume control
Main screen, Digital 1/2 selected, in phones mode
5. Operation

Manual UC1 © Grimm Audio
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takes place in the DSP of the loudspeaker. In all other
cases the volume control is in the DSP of the UC1. At
volume setting ‘+8’ the data to the digital output and
build-in DACs is put through transparently. At other
levels the digital gain control is properly dithered at 24
bits. Optionally, volume control of the main out can be
disabled in the menu. In that case the indicated monitor
gain only applies to the 2nd out and phones.
The knob to the right of the phones jack can be used to
align the headphones’ acoustic level with that of your
main monitor system. The idea is to switch between
speakers and phones (removing your headphones when
listening to the speakers) and adjust this control until
speakers and phones sound equally loud to you. From
then on just use the main dial for changing your
monitor gain and leave the phones control at its
calibrated level.
In the bottom left corner of the display the clock status
of the UC1 is indicated. When the UC1 is connected to a
computer via the USB connector on the back, these
settings are controlled from the computer Operating
System.
When the back USB is not connected to a computer, the
clock source can be set manually. Please refer to the
menu chapter for instructions. If the UC1 is set to slave
to an external source (BNC Word Clock, AES Digital 1 or
2), and it is not locked, the clock status turns red and
blinks.
The current function of the two small buttons is
indicated by the text on the display next to them. In the
main screen the bottom button gives access to the ‘soft
Metering screen, inputs & outputs view
5. Operation

Manual UC1 © Grimm Audio 19
key’ function, like switching to the ‘2nd out’. The top
button brings you into the menu. Since the rst menu
page oers access to various monitor tools, this button
may be used quite regularly. More details can be found
in the menu chapter.
Meters
In the main screen a simple three stage meter indicates
the current levels for all inputs and outputs and the
current monitor output. The stages are: -1 dBFS to show
you’re close to clipping; -14 dBFS which is the nominal
level of the UC1; -60 dBFS to show presence of signal.
In some cases the ‘ana 1|2’ input meters show signal
when no input signal is present. This is caused by DC
oset drift from the UC1 AD converters (a common
problem in most AD converter chips). Grimm Audio has
disabled the build-in high pass lters of the chip since
they aect the sound quality. Please remove this oset
in your DAW after recording, preferably with a tool that
subtracts the static average, instead of a high pass lter.
By press-holding the top ‘menu’ button, the display
changes from the main screen to the metering screen
with higher resolution meters. Another press-hold
brings you back to the main screen. In the metering
Metering screen, inputs view Metering screen, outputs view
5. Operation

Manual UC1 © Grimm Audio
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screen the two control buttons have a dierent
function: the top button enables cycling through the
three metering screens: inputs & outputs / inputs /
outputs (the latter two oer a larger view with more
detail, like channel names). The bottom button resets
the peak hold.
The meters are fast responding sample peak meters,
intended for quick evaluation of incoming and outgoing
levels. The nominal level is at -14 dBFS, which is +4 dBu
on the analog XLR’s. The rightmost meters in the “inputs
& outputs” and “outputs” screens shows the current
level and name of the monitor output. In the metering
screens the current monitor gain setting and destination
are indicated at the top in the middle. The monitor
source and clock status are indicated just like in the
main screen.
USB settings in the computer OS
The UC1 can be used with Macintosh, Windows and
Linux operating systems. It also works seemlessly with
iOS and Android devices, though these will usually only
be used with the second (stereo only) USB connector on
the front (the ‘i-put’).
Macintosh
Mac OS oers native support of UC1’s USB interface via
Core Audio, no driver is needed. All settings are
accessible via the Apple ‘Audio Midi Setup’ app. The UC1
‘Input’ page can be see on the right. All channels have
the names of the linked connectors on the UC1 back
Mac OS Audio Midi setup UC1 inputs page.
5. Operation