Celesonic US-20x20

USB3.0 Audio MIDI Interface with Mic Pre/Mixer

TASCAM’ Celesonic US-20x20 packs 20 channels of analog and digital I/O into a single rackspace with great sounding preamps and USB 3.0/2.0 connectivity. Eight Ultra-HDDA microphone preamps provide 56dB of gain and high headroom to make microphones sound their best. Up to ten channels of digital I/O are included on ADAT and S/PDIF connectors, with word clock also provided for use with external clocks like TASCAM’s CG-1000. MIDI I/O allows use with controllers and synthesizers, and sample rates up to 192kHz/24-bit are supported.

This model has been discontinued in North, Central and South America.
Please check the availability with your local distributors in other areas.

New Update: Settings Panel for Windows

TASCAM USB Audio Interfaces Driver (Settings Panel) software for Windows has been updated to Version 4.00, enabling to build music production environments with ultra-low latency that maximizes the processing power of the computers in use. In this new version, the driver’s stability has been greatly enhanced, the audio buffer size is now selectable up from 4 samples instead of older versions with the default buffer size of 64 samples, and overall usability has been improved.

* Version 4.00 functions are limited to Windows only.

Learn more

The TASCAM Celesonic US-20x20 is the first USB 3.0 interface to use class-compliant drivers for future-proof use with computers and tablets. A built-in DSP mixer includes parametric EQ and compression on every channel and a stereo reverb send for great-sounding monitor mixes. The DSP mixer can also be used as a live mixer or submixer with computer control. The US-20x20 has three operation modes – audio interface, digital mixer, and 8-channel digital mic preamp –for maximum flexibility.

Ultra-HDDA mic preamps deliver high headroom for dynamic tracks

Popularized in TASCAM's HS-P82 professional broadcast and film recorders, Ultra HDDA preamps have the performance to handle condenser, dynamic, and ribbon microphones. These versatile preamps also feature line-level inputs for keyboards and other equipment.

Sleek Industrial Design Inspires Creativity

We have applied the engineering expertise from years of making audio interfaces to create products that are both pioneering and practical. The slightly angled Bio-cell side panels provide users with excellent ergonomics and stimulate creativity. An adapter that supports rack-mounting is also included.

DSP mixer with 4-band EQ and compression on each input channel

Utilizing an Analog Devices BlackFin processor, the US-20x20 offers an advanced digital mixer. Every input has 4-band EQ, compressor, and low-cut filter. A stereo reverb processor is provided for dynamic headhone monitoring. The DSP mixer can store up to (10) snapshots as scenes - making it easy to recall mixer settings.

Three selectable modes included: interface/mic preamp/mixer

New functions added to Version 4.00
* Version 4.00 functions are limited to Windows only.

Audio buffer size selectable up from 4 samples

With conventional TASCAM drivers, the audio buffer size could only be set originally up from 64 samples. This has been enhanced to support a selection up from 4 samples, enabling users to build music production environments with ultra-low latency that maximizes the processing power of the computers in use. Users can now choose from a wide range of parameters, from a minimum of 4 samples up to a maximum of 2048 samples, depending on the computer's processing power and music production application.

Software window size optimization enabled by HiDPI support

The newly implemented HiDPI (high-dot per inch) function automatically optimizes the size of the Settings Panel window to an appropriate size according to the user's display. No more small appearing of the Settings Panel in a high-resolution display.

Ultra-HDDA mic preamps provide high headroom for dynamic tracks

TASCAM's Ultra-HDDA mic preamps provide up to 57dB of gain with the highest headroom in their class. Meaning your tracks won't be distorted before they even hit your computer, resulting in sweeter mids and deep soundstaging.
Popularized in TASCAM's HS-P82 professional broadcast and film recorders, Ultra HDDA preamps have the performance to handle condenser, dynamic, and ribbon microphones. These versatile preamps also feature line-level inputs for keyboards and other equipment.

Eight Ultra-HDDA Mic Preamps with 20dB of headroom

Ultra-HDDA (High Definition Discrete Architecture) mic preamps, an original TASCAM design, use discrete construction for superior audio quality. TASCAM has achieved an EIN rating of –125dBu (EIN is a value measurement of the absence of noise). The preamps have over 20dB of headroom, well above competing interfaces. This headroom is especially helpful on high SPL sources like drums and guitars.

With other ratings that include a signal-to-noise ratio of 104dB, we have achieved an extremely high level of audio performance. The key electronic components were selected through extensive listening tests.

Direct Inputs for Guitar and Bass

Two instrument-level inputs are provided for direct input of guitar or bass. Make the most of guitar effect plug-ins, such as the TH2 effect that is included with Cakewalk SONAR.

[Note] Guitar effect plug-ins and DAW software are sold separately.

High-grade Components Selected Through Careful Listening Tests

The TASCAM US Series interfaces have been engineered using the finest components available. Critical electronics such as the Audio4pro ADDA Converter by AKM Corporation enable the interface to boast a 104dB S/N ratio. TASCAM continues the legacy of creating products with professional high-end audio performance.

* Audio4pro is a brand name of AD converter by Asahi Kasei Microdevices Corporation - utilized in audio mixers and sound reinforcement equipment.

20 Inputs and 20 Outputs To Handle the Biggest Sessions

With 8 XLR/TRS inputs, 2 TRS inputs, multi-channel digital inputs via S/PDIF coaxial, and optical digital connectors, the US-20x20 provides a total of twenty simultaneous inputs when operating at 44.1kHz or 48kHz. Twenty simultaneous outputs are also transmitted from your DAW at 44.1kHz or 48kHz utilizing the 10 TRS line outputs, S/PDIF coaxial and optical digital outputs. The ADAT optical input/output support SMUX2 and SMUX4 - required for high sampling rates. Using two US-20x20 and the optical digital connections, it is possible to configure a 16-microphone recording system.

[Note] When operating at 88.2kHz or 96kHz, up to 16 inputs and 16 outputs are possible.
[Note] When operating at 176.4kHz or 192kHz, up to 12 inputs and 12 outputs are possible.

8 XLR/TRS inputs and 2 TRS inputs

The 8 XLR/TRS mic inputs have switchable +48V phantom power in banks of 4, making it possible to use 8 condenser mics at the same time. The 2 balanced line inputs on the rear of the unit are switchable between –10dBV and +4dBu. The user is able to interface an instrument of any level – balanced or unbalanced.

Word input/output enables connection with an external clock generator

With word clock BNC connection, synchronization with word clock BNC connection, with an external digital device is possible. A highly precise generator – such as one from the TASCAM CG Series – is recommended for complex system setups.

S/PDIF coaxial input/output

The product is equipped with S/PDIF coaxial input and output connectors for connection to effects processors, digital synths, or an external AD/DA converter. For a high-quality monitoring environment, the TASCAM DA-3000 Master Recorder / ADDA converter is recommended.

3 switchable modes - Interface, Mic Preamp and Mixer

The versatile Celesonic US-20x20 is an Interface for multitrack recording using a personal computer and DAW, a standalone mic preamp, or a mixer for live performances or mixing keyboards.

Mic Preamp Mode enabling use as a mic pre with analog & digital output

Mic Preamp Mode enables the use of the product as a standalone mic pre. In this mode, the XLR/TRS signal from the from panel flows through the Ultra-HDDA mic preamp, and is output through the TRS jack and the digital output on the rear panel. This is perfect for use into a mixer for live performances. It is not necessary to connect the interface to a personal computer via USB.

[Note] In Mic Preamp Mode, the sampling rate of the digital output is set to 44.1kHz. To change the sampling rate, a digital connection from a word clock master device must be established to the digital input connector.
[Note] When operating at 88.2kHz, 96kHz, 176.4kHz or 192kHz, the number of channels available from the optical digital connector is limited. At 88.2kHz and 96kHz, the output is limited to 4 channels - only the signals of IN1 through IN4 are available. At 176.4kHz and 192kHz, the output is limited to 2 channels - only the signals of IN1 and IN2 are available. And you can use only Optical or Coaxial. (All analog TRS output channels are available - IN1 through IN8)

Mixer mode enabling use for PA/SR and use as a keyboard mixer

Utilizing a 32-bit processing DSP mixer, the product can be used as a 6-bus mixer for PA/SR. In mixer mode, the US-20x20 provides an output patch bay and reverb effect. In mixer mode, the product is connected to a computer and the mixer is controlled from the computer. When two US-20x20 are connected, the result is a 16-channel digital mixer useful for live performances. In digital mixer mode, the motion of solo button provides "pre-fader-listen (PFL)".

[Note] When operating at 88.2kHz, 96kHz, 176.4kHz, or 192kHz, the numbers of inputs to and outputs from the optical digital connectors are limited.

Interface Mode for recording with a DAW

In Audio Interface Mode, the US-20x20 is used as a general audio interface connected to a personal computer, and used for recording with a DAW. The DSP mixer is enabled, and adjustment of dynamics such as balance, EQ, compression is possible during recording. In digital mixer mode, the motion of solo button provides "solo-in-place (SIP)".

[Note] When using the WDM driver, the number of output channels from an application is limited to less than 8 channels.

Advanced DSP mixer with EQ and compression on each channel

An obstacle with computer-based recording is latency (delayed audio signals). New USB 3.0 driver software has been developed to eliminate latency issues and driver set-up problems.
In addition, the built-in mixer provides near-zero latency monitoring while recording. It utilizes the high-performance Dual Core BlackFin DSP making it possible to offer 4-band EQ and compression on each channel. A stereo reverb is also provided for great-sounding headphone mixes.

[Note] When operating at 176.4kHz or 192kHz, the effects (EQ, compression, phase, and reverb) of the DSP mixer cannot be used.
[Note] USB3.0 connection requires Windows 10 or OS X 10.11.2 (or later).

High resolution recording up to 192Hz/24-bit

Record up to 192kHz/24-bit - which far exceeds CD quality (44.1kHz/16-bit). The product supports not only the increasing 96kHz/24-bit recordings but also recordings at higher sampling rates, so it can be used for a long time in the future.

USB 3.0 computer connection, a leading transmission standard

USB 3.0 is used in the US-20x20 for 24 channels transmission at 192kHz/24-bit. This is not possible with USB 2.0.

USB	OS
USB3.0/USB2.0	Windows 10
USB2.0	Windows 8, Windows 7, OS X Yosemite(10.10), OS X Mavericks(10.9), OS X Mountain Lion(10.8)

Advanced DSP mixer with 4-band equalizer and compressor on each channel

Utilizing an Analog Devices BlackFin processor, the US-20x20 offers an advanced digital mixer. Every input has 4-band EQ, compressor, and low-cut filter. The DSP mixer can store up to 10 snapshots as scenes – making it easy to recall mixer settings.

[Note] When operating at 176.4kHz or 192kHz, the effects (EQ, compression, phase, and reverb) of the DSP mixer cannot be used.

Reverb effect to enhance performance and recorded tracks.

The DSP mixer features reverb that can be used to enhance vocal and instrument recordings. The effect can be added to the monitored audio to enhance the performance while recording.

[Note] When operating at 176.4kHz or 192kHz, the effects (EQ, compression, phase, and reverb) of the DSP mixer cannot be used.

Driver software can be installed without connecting the interface

The Windows driver software can be installed without connecting the interface. The installation can be completed by simply following the on-screen instructions. On a Mac, the interfaces can be used without installing a driver, but it is recommend that the Setting Panel software be installed so useful settings can be made.

Sleek industrial design that inspires creativity

The versatile Celesonic US-20x20 is an Interface for multitrack recording using a personal computer and DAW, a standalone mic preamp, or a mixer for live performances or mixing keyboards.
We have applied the engineering expertise from years of making audio interfaces to create products that are both pioneering and practical. With their distinctive styling, these interfaces fit perfectly on the desktops of musicians and stimulate creativity.

Tascam’s new US series satisfies the needs of musicians from an aesthetic as well as ergonomic perspective. With its unique honeycomb structure on the side panels, the main body has a sense of weight, while also maintaining a delicacy that matches the user’s needs. Honeycomb structures are a feature of modern architecture, but are also a vital resource whose exceptional technical structure we can use in design. As this structure is found in nature, it has a stability and flexibility which comes with being an organic form.
-Axel Hartmann@ designbox

designbox (Official Website) : A German audio design company founded by Axel Hartmann and Stephan Leitl in 1995 which has worked on several design projects for famous music industry products such as synthesizers, effect pedals and amp simulators.

Angled design provides excellent usability on a desktop

The angled design of the US-20x20 makes desktop viewing and operation much easier than a flat box on a table. No more stretching the neck or twisting the wrist to operate an interface.

Separate volume controls for headphones and line output

The interfaces are designed with separate headphone and line output volume controls so even when both powered monitors and headphones are connected, the user can set an optimum level for each during operation.

Built to tough robust full metal body

The durable metal jacket is employed for heavy duty use.

Dual 70mW + 70mW Headphone Outputs

The high-output 70mW + 70mW (into 32Ω) headphone amplifiers makes headphone monitoring easy, during loud sessions. This assures you enough monitoring volume even while recording in the same room of a rehearsal studio.

Rackmount Adapters and hex keys are included

The US-20x20 is supplied with the biocell side panels, but TASCAM also includes rack ears and a hex wrench - making it easy to remove the side panels and rackmount the interface if desired.

Class-compliant Drivers Support iPads and other Tablets

You will not need another audio interface if you decide you want to make music using an iPad or other iOS device. The performance of these interfaces has been tested with major DAWs – you can continue to use them even if you change DAW software. Since these units include MIDI inputs and outputs, they can also be used as MIDI interfaces.

Connect with an iPad or another iOS device

Use a genuine Apple Lightning-USB camera adapter to connect the unit to an iPad or other iOS device.

[Note] A genuine Apple Lightning-USB camera adapter is not included with this product.
[Note] When connected, the US-20x20 will not provide power to the iOS device.

Tested with Sonar, Pro Tools, Cubase, Live, Studio One, and GarageBand, Logic Pro

TASCAM has tested the interface operation with popular DAWs.

MIDI input and output enable connection with keyboards and other MIDI devices

MIDI input and output connectors allow connection with keyboards and other sound sources that employ MIDI connectors. The interfaces can also be used for synchronized operation of multitrack recorders and other external recording equipment.

Features at a Glance

Ultra-HDDA (High Definition Discrete Architecture) mic preamps with −125dBu EIN
Eight Ultra-HDDA micpres with XLR/TRS and connector, two TRS inputs
3 mode switching of Interface/Mic preamp/Mixer
Up to 192kHz/24-bit recording
Support for Windows and Mac
USB 3.0/2.0 computer connection (USB3.0 requires Windows 10)
Connect with iPads and other iOS devices
+48V phantom power for all inputs
High-impedance inputs available
Input level specifications boast a range of 56 dB for using dynamic mics
Tough metal casing for durability
Angled design provides excellent usability on a desktop
Two standard TRS headphones output jack with 70mW + 70mW output power
Separate controls for line and headphones output volumes
MIDI input and output
Low-latency monitoring via on-board DSP mixer
DSP mixer with 4-band EQ and compression on each input channel(Can be used in Interface/Mixer mode)
On-board Reverb effect ideal for monitoring on interface mode or PA/SR on mixer mode
Patch bay allows outputs to be assigned freely(Can be used in Interface/Mixer mode)
Scenes can store DSP mixer settings (up to 10+1 scenes can be stored and named）
Ten TRS analog outputs
S/PDIF coaxial digital input/output connectors
TOS LINK optical digital multichannel input/output connectors (supporting SMUX2 and SMUX4)
BNC word clock input/output connectors
USB class compliant 2.0 support
Confirmed operation with major DAW software (SONAR, Pro Tools, Cubase, Live, Studio One, GarageBand, Logic Pro）
RoHS certified
Rack-mount adapter included
Dedicated AC adapter included
USB2.0 cable and USB3.0 cable included

Information regarding Windows 11 Version 23H2 compatibility

Learn More

[Updated] Information about macOS Sonoma Update

Learn More

Spec description

	US-16x08	US-20x20
Sampling frequency	44.1k/48k/88.2k/96k Hz	44.1k/48k/88.2k/96k/176.4k/192k Hz
Quantization bit rate	16/24bit
Analog audio inputs (Front)
MIC IN (BALANCED)	IN 1-8
Connector	XLR-3-31(1:GND, 2:HOT, 3:COLD)
Input impedance	2.4k ohms
Nominal input level
GAIN:MAX	-68dBu (0.0003Vrms)
GAIN:MIN	-12dBu (0.195Vrms)
Maximum input level	+8dBu (1.947Vrms)
Gain	56dB
INST IN (UNBALANCED)	IN 9-10	IN 1-2
Connector	6.3mm(1/4") TS-jack(T:HOT, S:GND) (When set to "INST" at LINE/INST switch)
Input impedance	1M ohms or more
Nominal input level
GAIN:MAX	-57dBV (0.0014Vrms)	-68dBV (0.0004Vrms)
GAIN:MIN	-12dBV (0.251Vrms)
Maximum input level	+8dBV (0.2512Vrms)
Gain	45dB	56dB
LINE IN (BALANCED)	IN 9-10 (When set to "LINE" at LINE/INST switch)	IN 3-8
Connector	6.3mm(1/4") TRS-jack(T:HOT, R:COLD, S:GND)
Input impedance	10k ohms
Nominal input level
GAIN:MAX	-41dBu (0.0069Vrms)
GAIN:MIN	+4dBu (1.228Vrms)
Maximum input level	+24dBu (12.282Vrms)
Gain	45dB	56dB
Analog audio inputs (Rear)
LINE IN (UNBALANCED)	IN 11-16	IN 9-10
Connector	6.3mm(1/4") TS-jack(T:HOT, S:GND) (When set to "-10dBV" at LEVEL switch)
Input impedance	10k ohms or more
Nominal input level	-10dBV (0.3162Vrms)
Maximum input level	+10dBV (3.162Vrms)
LINE IN (BALANCED)	IN 11-16	IN 9-10
Connector	6.3mm(1/4") TRS-jack(T:HOT, R:COLD, S:GND) (When set to "+4dBu" at LEVEL switch)
Input impedance	10k ohms
Nominal input level	+4dBu (1.228Vrms)
Maximum input level	+24dBu (12.1282Vrms)
Digital audio inputs
COAXIAL
Connector	-	RCA pin jack
Format	-	IEC60958-3(S/PDIF)
Input impedance	-	75 ohm
Input level	-	0.5Vp-p / 75 ohm
OPTICAL (S/MUX)
Connector	-	OPTICAL (JEITA RC-5720C)
Format	-	Multi-channel optical format (S/MUX4 is available in 88.2k/96k/176.4k/192k Hz)
Analog audio outputs
LINE OUT (BALANCED)	OUT 1-8	OUT 1-10
Connector	6.3mm(1/4") TRS-jack(T:HOT, R:COLD, S:GND)
Output impedance	100ohms
Nominal output level	+4dBu (1.228Vrms)
Maximum output level	+24dBu (12.277Vrms)
Digital audio outputs
COAXIAL
Connector	-	RCA pin jack
Format	-	IEC60958-3(S/PDIF) / IEC60958-4(AES/EBU)
Input impedance	-	75 ohm
Input level	-	0.5Vp-p / 75 ohm
OPTICAL (S/MUX)
Connector	-	OPTICAL (JEITA RC-5720C)
Format	-	Multi-channel optical format (S/MUX4 is available in 88.2k/96k/176.4k/192k Hz)
MIDI IN / OUT
Connector	Din 5-pin
Format	Standard MIDI format
WORD IN
Connector	-	BNC Permissible frequency deviation at the time of external synchronization
Input voltage	-	2.0Vpp to 5.0Vpp
Input impedance	-	75 ohm +/-10%
Input level	-	+/-100ppm
WORD OUT
Connector	-	BNC with OUT/THRU select switch
Output voltage	-	2.0Vpp (75ohm loaded)
Output impedance	-	75 ohm +/-10%
Sampling frequency	-	44.1k/48k/88.2k/96k/176.4k/192k Hz
USB
Connector	USB B type 4-pin	USB3.0/2.0 B type
Format	USB2.0 HIGH SPEED mass storage class	USB3.0 SuperSpeed (5Gbps)/USB2.0 HIGH SPEED (480Mbps)
PHONES
Connector	6.3mm(1/4") stereo phone jack
Maximum output level	70mW+70mW or more (THD+N 0.1% or less, 32ohms loaded)
Power	Dedicated AC adapter (GPE248-120200-Z, included)
Power consumption	12W	20W
Dimensions	52(W) ×2.32(H) ×8.62(D) inch 445(W) ×59(H) ×219(D) mm	52(W) ×2.32(H) ×8.7(D) inch 445(W) ×59(H) ×222(D) mm
Weight	2.8kg / 6.11lb	2.7kg / 5.95lb
Operating temperature	5 to 35˚C
Accessories	Rack mount adapter, USB cable, User's manual, warranty card, dedicated AC adapter (GPE248-120200-Z)	Rack mount adapter, USB2.0 cable, USB3.0 cable, User’s manual, warranty card, dedicated AC adapter

Audio performance

Frequency response
LINE OUT(BALANCED)
44.1k/48k Hz	20Hz to 20kHz, +/-0.3dB(JEITA)
88.2k/96k Hz	20Hz to 40kHz, +/-0.3dB(JEITA)
176.4k/192k Hz	-	20H to 80kHz、+/-0.5dB(JEITA)
THD	0.008% or less	0.005% or less
S/N ratio	100dB or more	104dB or more
Crosstalk	100dB or more

Computer system requirements

Windows

Compatible computers	Windows-compatible computer with a USB 2.0 port	Windows-compatible computer with a USB 2.0 or USB3.0 port
CPU type/speed	Dual core/2 GHz or faster
Memory	2GB or more
DRIVER	ASIO2.0, WDM(MME), MIDI	USB Audio Class 2.0, ASIO2.0, WDM(MME), MIDI Note: When using WDM driver, number of output channels from an application has limitation less than 8 channels.
Screen resolution	1280 x 800 Dot or more

Mac

Compatible computers	Apple Mac computer with a USB 2.0 port	Apple Mac computer with a USB 2.0 or USB3.0 port
CPU type/speed	Dual core/2 GHz or faster
Memory	2GB or more
DRIVER	Core Audio, Core MIDI
Screen resolution	1280 x 800 Dot or more

Supported OS'

Windows

Windows 11 2023 Update (Version 23H2) New , Windows 10 2022 Update (Version 22H2) , Windows 11 2022 Update (Version 22H2) , Windows 11 (Version 21H2) , Windows 10 (November 2021 Update) , Windows 10 (May 2021 Update) , Windows 10 (October 2020 Update) , Windows 10 (May 2020 Update) , Windows 8.1 , Windows 8 , Windows 7

Mac

macOS Sonoma New , macOS Ventura , macOS Monterey , macOS Big Sur , macOS Catalina , macOS Mojave , macOS High Sierra (10.13) , macOS Sierra‎ (10.12) , OS X El Capitan (10.11) , OS X Yosemite (10.10) , OS X Mavericks (10.9) , OS X Mountain Lion (10.8)

iOS

iPadOS 17 New , iOS 17 New , iOS 16 , iPadOS 16 , iOS 15 , iPadOS 15 , iPadOS 14 , iOS 14 , iPadOS 13 , iOS 13 , iOS 12 , iOS 11 , iOS 10 , iOS 8

Information

Latest version info
Settings Panel for Windows	V4.00
Settings Panel for Mac	V2.10
Firmware	V2.00

Settings Panel V4.00 for Windows

Buffer Size can now be set from 4 samples.
Scaling to a suitable size now occurs with 4K and other high resolution displays.
Operation stability has been improved.

Notices About Products

11-14-2023 Information regarding Windows 11 Version 23H2 compatibility

10-24-2023 [Updated] Information about macOS Sonoma Update

10-02-2023 [Updated] Information about iOS 17, iPadOS 17 Update

Spec

Outline (DXF)	07-29-2016	2.1 MB

Manuals

Reference Manual V2.10	12-07-2016	6.2 MB
Owner's Manual	07-29-2016	15.4 MB
Reference Manual	07-29-2016	6.2 MB

Documents

Release Note	02-19-2020	5.0 KB
Software/Firmware Update procedures	11-08-2016	1023.6 KB

Firmware

Firmware V2.00 for Windows	11-08-2016	15.1 MB
Firmware V2.00 for Mac	11-08-2016	12.8 MB

Software

V4.00 Settings Panel for Windows (Includes driver)	02-19-2020	18.3 MB
V2.10 Settings Panel for Mac	12-07-2016	14.9 MB

Images

High resolution images	07-18-2019	14.2 MB

FAQs

My interface keeps switching itself off, is it broken?

Make sure that the "Auto Power Save" switch on the rear panel is set to off. It is set to on by default (for CE complience.)

Occasionally, my software says that the US-20x20 is no longer connected. How do I fix this?

Download and install firmware version 1.01 or later for your device from the downloads page.

How do I get the US-20x20 to function at 192kHz sampling rate?

To enable the US-20x20's 192kHz mode:

Open the Audio/MIDI Setup app inside your Applications/Utilities folder.
Select the US-20x20 in the list on the left side of the window.
Make sure that the Input tab is selected. Click on the menu that says "20ch-24bit Integer" and change it to "12ch-24bit Integer"
Select the "Output" tab and repeat the above step.
Open your DAW software. You should have 192kHz as an option.

Note that the limitation of 12-channels at 192kHz is because the ADAT Optical format is limited in that way. It functions as 8-channel in 48kHz, 4-channel at 96kHz, or 2-channel at 192kHz.

I'm using OSX Mountain Lion (10.8) and the mixer panel is not working correctly, how do I fix this?

This is fixed in settings panel version 1.01 or later. It's a free update on the downloads page.

I want to use external clocking on the US-20x20 in mic preamp mode, how do I set this up?

You need to connect the US-20x20 to a computer to set clocking, sample rate, and other settings – even in mic preamp mode. Open the US-20x20 Settings Panel application to change this.

I plugged in my interface using the USB3 cable and I don't hear any audio?

As of this writing, USB 3 only works on the Windows 10 OS. TASCAM is using a class-complient driver, which means that we have no control over bug fixes in the OS. Apple is working on this issue and is hoping to fix it in an upcoming update to OSX 10.11 El Capitan. Please note that there is no reduced feature set when working in USB 2 mode, including channel count and latency.

When playing files that are of different sampling frequencies from a computer or iOS device, the audio may not start playing, the beginning of the sound may be cut off, or noise/crashing may occur.

Your device's playback application/software, and playback file frequencies (sampling frequency) may not be matching. Set the frequencies of the playback file and each configuration to be the same, or unify the frequencies of the playback file.

When the computer or iOS device etc. goes into sleep mode, the interface USB LED may blink or turn off and not opertate properly when the external device recovers from sleep mode.

Depending on the usage environment, reboot the interface by turning the power off/on again, or disconnect and reconnect the USB cable.