Avid Mbox Pro, Mbox, Mbox Mini Audio Interface Technology Guide

Third-Generation Mbox
Technology Guide
Table of Contents
Design Philosophy Behind the Third-Generation Mbox Family......................................................3
The Elements of a Great Audio Interface.......................................................................................3
Converters..................................................................................................................................3
Preamps......................................................................................................................................3
Clocking......................................................................................................................................3
Emissions Compliance................................................................................................................3
The Keys to the Mbox Sound.........................................................................................................4
Listening Tests............................................................................................................................4
Premium Components and Efficient Layout................................................................................4
World-Class Clocking and Jitter-Elimination Technology............................................................4
Industrial and Electrical Design...................................................................................................4
Power..........................................................................................................................................4
Hardware Build...........................................................................................................................4
Expertise.....................................................................................................................................5
Signal Path, Internal Layout, and Routing......................................................................................6
Mbox Pro Signal Path.................................................................................................................7
Mbox Signal Path........................................................................................................................7
Mbox Mini Signal Path................................................................................................................7
Additional Resources.....................................................................................................................8
Appendix........................................................................................................................................9
Mbox Family Specification Comparison......................................................................................9
Mbox Pro Input Frequency Response..................................................................................... 10
Mbox Pro Output Frequency Response................................................................................... 10
Mbox Pro Input THD.................................................................................................................11
Mbox Pro Output THD..............................................................................................................11
Mbox Input Frequency Response............................................................................................ 12
Mbox Output Frequency Response......................................................................................... 12
Mbox Input THD....................................................................................................................... 13
Mbox Output THD.................................................................................................................... 13
Mbox Mini Input Frequency Response.................................................................................... 14
Mbox Mini Output Frequency Response.................................................................................. 14
Mbox Mini Input THD............................................................................................................... 15
Mbox Mini Output THD............................................................................................................ 15
Design Philosophy Behind the Third-Generation Mbox Family
In designing the new Avid® Mbox® family of audio interfaces, our industry-leading engineering team set out
to create best-in-class products that would surpass their previous efforts in this category—as well as those
of other manufacturers. To meet this goal, we leveraged technology from our top-of-the-line Pro Tools|HD
recording systems, and also drew from our extensive experience developing mobile recording solutions.
In addition, we conducted numerous customer surveys and interviews, and incorporated a broad array of
user requests into the new Mbox series—from higher audio quality and enhanced integration with Pro Tools®
software, to a rock‑solid new chassis and ergonomic front-panel design. Finally, we carefully optimized each
member of the Mbox family for its specific function—from serious desktop production to mobile field work.
The Elements of a Great Audio Interface
It’s important to understand the reasons why some interfaces sound better than others, even when recording
at equal sample rates and bit depths. Much of the answer lies in the quality of the components.
Converters
Even if the performers, instruments, rooms, and microphones are excellent, a recording can suffer if the
interface uses poor-quality converters to convert between the analog and digital domains. Low-quality
converters create noise and distortion, which degrade the quality of the recording. Excellent converters
deliver pure, powerful sound, even when the final playback medium is only 16 bits.
Preamps
It’s important to use preamps that deliver high gain without introducing unwanted noise and hiss from
their internal circuitry. This provides clean, natural-sounding audio regardless of how much gain is
required. The signal-to-noise ratio* (expressed in negative values) is an important gauge of the quality
of an interface’s converters and preamps; lower (more negative) numbers indicate better performance.
Clocking
Audio interfaces must clock their converters at regular intervals in order to capture sound accurately.
A poorly designed clock can breed jitter, causing the interface to sample audio irregularly. The irregularity
results in audio distortion. An excellent clock has minimal jitter, ensuring that the digital audio converters
stay rigidly time-locked and minimize related distortion.
Emissions Compliance
An excellent audio interface will be designed and manufactured to ensure that electronic emissions
comply with the emission limits set by national and international standards agencies. It will also comply
with the requirements to continue to properly operate with specified levels of emissions from nearby
electrical and electronic equipment.
It’s not enough to just use premium-quality components—it’s absolutely critical to arrange and connect them
with the utmost precision and expertise. This requires a deep level of experience and specialized training.
*Beware when comparing signal-to-noise specs from different manufacturers. Some companies only measure the noise
introduced by the preamps and ignore the complete signal path; others state the theoretical specs of the converters and not
the actual measured specs. This results in a signal-to-noise ratio that is misleading. Avid publishes only “real-world” specs,
so users will know how the interface will truly perform before making a purchase.
3
The Keys to the Mbox Sound
Listening Tests
Before commencing work, our design team engaged in a series of listening tests. We sampled Avid
interfaces as well as products from other manufacturers, then worked to develop the clearest, most
transparent-sounding interfaces possible. With each subsequent revision of the electronics, our team
reconvened for another set of exhaustive listening tests to ensure exceptional performance.
Premium Components and Efficient Layout
Our engineers started by selecting the best possible components. They sourced the finest D-A and A-D
converters, as well as crystal-clear preamps for pure, pristine sound from start to finish. Then they worked
to ensure the shortest possible path between components, resulting in superior audio quality. (See signal
path diagrams in “Signal Path, Internal Layout, and Routing” section.)
World-Class Clocking and Jitter-Elimination Technology
The Mbox Pro interface features critically acclaimed JetPLL technology to provide extremely stable
synchronization and eliminate jitter that can degrade audio quality. The Mbox and Mbox Mini interfaces
also feature high-quality clocks to provide accurate, low-jitter audio sampling and exceptionally low
resulting distortion.
Industrial and Electrical Design
Our engineering team worked hand in hand with our industrial designers to pair an aesthetically pleasing
and ergonomic exterior with optimized internal electronics and connections. We carefully considered the
position of every element. For example, we placed the preamp jacks on the same side of the interface as
the gain pots and controls in order to ensure the shortest possible internal path—rather than routing them
amongst other components that could introduce noise and interference. We fine-tuned every detail, down
to the routing of every copper trace on the printed circuit boards. We spent months balancing the external
design with the internal, in order to deliver an intuitive user experience as well as pristine sound.
Power
Since the Mbox Pro interface is intended for project studio use, it features an extremely efficient,
low-noise power supply. In contrast, the Mbox and Mbox Mini each feature state-of-the-art bus power
architecture in order to deliver high performance during mobile use, as well as in the studio.
Our engineering team paid exceptional attention to detail when considering the power requirements
for each Mbox interface. All microphones draw different levels of power, so we started by sampling a
wide variety of popular mics to understand the range of power needs. Then we designed the interfaces
to provide adequate phantom power for all possible mics, with a slight bit of headroom. We carefully
selected every single power‑drawing component in the interfaces, continually minding the overall power
budget. Then we pored over the schematics to analyze hot spots, and cut back wherever possible to
ensure power efficiency—without ever compromising performance.
Hardware Build
In direct response to customer feedback, the third-generation Mbox interfaces are housed in
professional‑grade, rugged, metal chassis designed to withstand the rigors of heavy-duty mobile and
studio use. All structural components are made of metal; a solid metal extrusion encases a secondary
inner metal chassis, which ensures the precise alignment of all internal components. In addition, the
metal enclosure—along with proper circuit design, filtering, and layout—provides immunity to emissions
from nearby electronics equipment, keeping the sound quality pristine. A molded plastic faceplate and
soft-touch knobs enhance the aesthetic and tactile appeal.
4
Expertise
Our engineering team relied on their personal experience as musicians and audiophiles to ensure that
the Mbox interfaces would yield pleasing, musical results in even the most demanding circumstances.
For example, if pushed to the point of distortion when capturing heavy vocals, the distortion sounds
musical rather than harsh. These audible performance characteristics further separate Mbox from
products by other manufacturers.
Like our engineering team, our testing department is full of working musicians, audio engineers, and
audiophiles. These power-users rigorously tested the interfaces to make sure that they would perform
optimally in a vast array of real-word scenarios—with a wide variety of computers, operating systems,
microphones, and other gear. After standing up to their discerning ears and uncompromising scrutiny,
we knew the Mbox interfaces would meet the sonic expectations of even the most demanding users.
5
Signal Path, Internal Layout, and Routing
In addition to selecting premium components and creating the shortest possible signal path between them,
our engineers worked to optimize each model’s signal chain for its intended use, as detailed below.
Mbox Pro Signal Path
The Mbox Pro audio interface features 8 x 8 simultaneous channels of I/O. There are four microphone
inputs with 48V phantom power (two XLR/DI combo, two XLR), plus four 1/4” TRS line inputs. The DSP and
software‑based mixer lie at the heart of the Mbox Pro interface, facilitating a huge variety of routing options.
The mixer also provides access to a variety of hardware-based low-latency effects.
6
Microphone Input
The signal goes from the XLR input into a premium-quality preamp with a pad, which provides over
74 dB of gain range (including the 20 dB pad). From there, the signal goes to a high-pass filter, which is
controlled by software via a high-quality relay. Then the signal passes to an insert jack on the back of the
interface, so the user can send to external devices, and the return will come in through the same insert.
Line Input
The Mbox Pro interface is specifically optimized for desktop recording scenarios, where a user is likely to
leave the line inputs plugged in at all times. A Front/Rear switch enables the user to choose between the
preamp signals or line inputs on the back of the interface. The signal from the line input does not pass
through the preamp; instead it connects directly to the converter, ensuring that the sound is not colored
in any way. The line input features a +4/-10 switch so a user can switch between professional- and
consumer-level signals.
Then, users have the option of passing the signal to the soft-clip limiter, which features the same
technology as our top-of-the-line Pro Tools|HD 192 I/O audio interface, enabling users to track
extremely hot signals without overloading the inputs and clipping. Finally, the signal feeds directly to
the premium-quality A/D converter, which delivers world‑class performance.
Instrument Input
The instrument input follows the same path as the microphone input, and thereby benefits from the same
wide gain range and control via the gain knob. The instrument input is optimized to cover a wide range
of signal strengths and output levels (passive and active guitars, etc.). The dynamic range and distortion
specs are dramatically improved compared to the previous generation.
Mbox Signal Path
7
The Mbox interface provides 4 x 4 simultaneous channels of I/O—two XLR mic/line combo inputs
with 48V phantom power, and two 1/4” DI inputs on the front panel for easy access. The Mbox signal
path is designed to offer optimum flexibility for mobile scenarios and field use. The line inputs pass
through the preamps, so users can plug in a variety of sources and just tweak the gain as needed.
The high-quality preamp does not color the signal, and the placement of the mic and line inputs on the
same circuit ensures that no additional noise is introduced. As a result, the Mbox delivers clear, pristine
sound. The mixer also provides access to a variety of hardware-based low-latency effects.
Mbox Mini Signal Path
With 2 x 2 simultaneous channels of I/O, the Mbox Mini interface is designed to be a high-quality,
personal, portable interface. It’s built for simplicity, and optimized to deliver clean, clear performance.
Its twin preamps accept a combination of mic, instrument, and line inputs, and provide exceptional
quality like those found on the Mbox Pro and Mbox interfaces.
Additional Resources
From the powerhouse Mbox Pro to the ultra-compact Mbox Mini, the new family of Mbox interfaces delivers
unparalleled sound quality and flexibility for today’s recording enthusiasts. For more information about each
model, visit www.avid.com/MboxFamily.
8
Appendix
As with all Avid product specifications, the published Mbox specs reflect actual performance measurements.
Mbox Family Specification Comparison
Line Inputs (Balanced)
Freq Response, 20 Hz - 20 kHz
Dynamic Range (A-wt)
SNR (A-wt)
THD+N, 1 k, -1 dBFS
Crosstalk at 1 k
Mbox Pro
Mbox
Mbox Mini
+/-0.1 dB
110 dB
-110 dB
-100 dB
-120 dB
+/-0.1 dB
106 dB
-106 dB
-94 dB
-116 dB
+4.2 dBu
+0 dBu
10 k (20 k)
10 k (20 k)
Min Gain, No Pad
+/-0.1 dB
110 dB
-110 dB
-100 dB
-128 dB
-120 dB
+0.5 dBu
+20.5 dBu
1.8 k (3.6 k)
54 dB
(74 dB with Pad) -20 dB
Min Gain, No Pad
+/-0.1 dB
110 dB
-110 dB
-100 dB
-128 dB
-120 dB
+4.2 dBu
+24.2 dBu
2.2 k (4.4 k)
54 dB
(74 dB with Pad) -20 dB
Min Gain, No Pad
+/-0.1 dB
106 dB
-106 dB
-94 dB
-128 dB
-116 dB
+0 dBu
+20 dBu
2.2 k (4.4 k)
54 dB
(74 dB with Pad)
-20 dB
Min Gain, No Pad
+/-0.1 dB
109 dB
-109 dB
-98 dB
-120 dB
+16 dBV
1 Mohm
54 dB
(74 dB with Pad)
-20 dB
Min Gain, No Pad
+/-0.1 dB
109 dB
-109 dB
-98 dB
-120 dB
+16 dBV
1 Mohm
54 dB
(74 dB with Pad)
-20 dB
Min Gain, No Pad
+/-0.1 dB
105 dB
-105 dB
-94 dB
-110 dB
+16 dBV
1 Mohm
54 dB
(74 dB with Pad)
-20 dB
Aux Inputs (Unbalanced)
Freq Response, 20 Hz - 20 kHz
Dynamic Range (A-wt)
SNR (A-wt)
THD+N, 1 k, -1 dBFS
Crosstalk at 1 k
Maximum Input Level
Input Impedance
+/-0.1 dB
105 dB
-105 dB
-98 dB
-120 dB
+2 dBV
10 k
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
Line Outputs (Balanced)
Freq Response, 20 Hz - 20 kHz
Dynamic Range (A-wt)
SNR (A-wt)
THD+N, 1 k, -1 dBFS
Crosstalk at 1 k
Maximum Output Level
Max Level
+/-0.1 dB
109 dB
-109 dB
-102 dB
-120 dB
+14 dBu
Max Level
+/-0.1 dB
109 dB
-109 dB
-102 dB
-110 dB
+10.2 dBu
Max Level
+/-0.1 dB
109 dB
-109 dB
-93 dB
-110 dB
+10.2 dBu
Headphone Outputs
Freq Response, 20 Hz - 20 kHz
Power into Ohms
Max Level, 32 R
+/-0.2 dB
60 mW into 32 R
Max Level, 32 R
+/-1.0 dB
20 mW into 32 R
Max Level, 32 R
+/-0.2 dB
20 mW into 32 R
+/-0.1 dB
112 dB
-112 dB
-100 dB
-120 dB
+14
dBu
/ +6 dBV
Maximum Input Level
(switched)
Input Impedance
10 k (20 k)
Mic Inputs (Balanced)
Freq Response, 20 Hz - 20 kHz
Dynamic Range (A-wt)
SNR (A-wt)
THD+N, 1 k, -1 dBFS
EIN Unwtd, 54 dB gain, 150 R
Crosstalk at 1 k
Max Input Level (No Pad)
Max Input Level (With Pad)
Input Impedance
Gain Range
Pad in dB
Inst Inputs (Unbalanced)
Freq Response, 20 Hz - 20 kHz
Dynamic Range (A-wt)
SNR (A-wt)
THD+N, 1 k , -1 dBFS
Crosstalk at 1 k
Max Input Level
Input Impedance
Gain Range
Pad in dB
9
1
2
Red
Solid
3
DSP Anlr.Level B
Left
Line Outputs, -10dBu @1kHz
Output Freq Resp.at27
Frequency Response and Total Harmonic Distortion (THD)
Mbox Pro Input Frequency Response
AVID
Mbox Pro
+1
+0.8
+0.6
+0.4
+0.2
d
B
r
+0
1
-0.2
-0.4
-0.6
-0.8
-1
20
20k
50
100
200
500
1k
2k
5k
10k
20k
1k
2k
5k
10k
20k
Hz
Sweep
Trace
Color
Line Style
Thick
Data
Axis
1
1
1
2
Blue
Red
Solid
Solid
3
3
DSP Anlr.Level A
DSP Anlr.Level B
Left
Left
Mbox Pro Output Frequency Response
AVID
Comment
Mbox Pro
Mic Inputs, Min Gain
Input Freq Resp.at27
-9
-9.2
-9.4
-9.6
-9.8
d
B
u
-10
-10.2
-10.4
-10.6
-10.8
20k
-11
20
50
100
200
500
Hz
Sweep
Trace
Color
Line Style
Thick
Data
Axis
1
1
1
2
Blue
Red
Solid
Solid
3
3
DSP Anlr.Level A
DSP Anlr.Level B
Left
Left
Line Outputs, -10dBu @1kHz
Comment
10
Output Freq Resp.at27
1
2
Red
Solid
3
Fft.Ch.2 Ampl
Left
1
THD (-1dBFS signal) FFT, Line Outputs
L
Output THD FFT.at27
Mbox Pro Input THD
AVID
AVID
Mbox Pro
+0
+1
-10
+0.8
-20
-30
+0.6
-40
+0.4
-50
-60
+0.2
-70
d
B
F
S
-80
d
B
r
-90
1
+0
-0.2
-100
-110
-0.4
-120
-0.6
-130
-140
-0.8
-150
-160
20
50
100
200
500
1k
2k
5k
10k
-1
20
20k
Hz
Sweep
Trace
Color
Line Style
Thick
Data
Axis
1
1
1
2
Blue
Red
Solid
Solid
3
3
Fft.Ch.1 Ampl
Fft.Ch.2 Ampl
Left
Left
Mbox Pro Output THD
AVID
Comment
S
1
1
AVID
Mbox Pro
THD (-1dBFS signal) FFT, Mic Inputs, Min Gain
M
THD FFT.at27
-9
+10
+0
-9.2
-10
-9.4
-20
-30
-9.6
-40
-9.8
-50
d
B
u
-60
d
B
u
-70
-80
-10
-10.2
-90
-10.4
-100
-110
-10.6
-120
-10.8
-130
-140
20
50
100
200
500
1k
2k
5k
10k
20k
-11
20
Hz
Sweep
Trace
Color
Line Style
Thick
Data
Axis
1
1
1
2
Blue
Red
Solid
Solid
3
3
Fft.Ch.1 Ampl
Fft.Ch.2 Ampl
Left
Left
THD (-1dBFS signal) FFT, Line Outputs
Comment
S
1
1
11
Output THD FFT.at27
L
1
2
Red
Solid
3
Fft.Ch.2 Ampl
1
Left
L
THD (-1dBFS signal) FFT, Line Outputs
Output THD FFT.at27
Mbox Input Frequency Response
AVID
Mbox
AVID
+0
+1
-10
+0.8
-20
-30
+0.6
-40
+0.4
-50
-60
+0.2
d
B
r
d
B
F
S
+0
1
-0.2
-70
-80
-90
-100
-110
-0.4
-120
-0.6
-130
-140
-0.8
-150
-1
20
50
100
200
500
1k
2k
5k
10k
20k
-160
20
Hz
Sweep
Trace
Color
Line Style
Thick
Data
Axis
1
1
1
2
Blue
Red
Solid
Solid
3
3
DSP Anlr.Level A
DSP Anlr.Level B
Left
Left
Mbox Output Frequency Response
AVID
Comment
S
1
1
Mbox
Mic Inputs, Min Gain
T
Input Freq Resp.at27
-9
-9.2
-9.4
-9.6
-9.8
d
B
u
-10
-10.2
-10.4
-10.6
-10.8
20k
-11
20
50
100
200
500
1k
Hz
Sweep
Trace
Color
Line Style
Thick
Data
Axis
1
1
1
2
Blue
Red
Solid
Solid
3
3
DSP Anlr.Level A
DSP Anlr.Level B
Left
Left
Line Outputs, -10dBu @1kHz
Comment
12
Output Freq Resp.at27
2k
5k
10k
20k
1
2
Red
Solid
3
DSP Anlr.Level B
Left
Line Outputs, -10dBu @1kHz
Output Freq Resp.at27
Mbox Input THD
AVID
Mbox
+0
-10
-20
-30
-40
-50
-60
-70
d
B
F
S
-80
-90
-100
-110
-120
-130
-140
-150
-160
20
20k
50
100
200
500
1k
2k
5k
10k
20k
Hz
Sweep
Trace
Color
Line Style
Thick
Data
Axis
1
1
1
2
Blue
Red
Solid
Solid
3
3
Fft.Ch.1 Ampl
Fft.Ch.2 Ampl
Left
Left
Mbox Output THD
AVID
Comment
AVID
Mbox
THD (-1dBFS signal) FFT, Mic Inputs, Min Gain
THD FFT.at27
-9
+10
+0
-9.2
-10
-9.4
-20
-30
-9.6
-40
-9.8
-50
d
B
u
-60
d
B
u
-70
-80
-10
-10.2
-90
-10.4
-100
-110
-10.6
-120
-10.8
-130
-140
20
50
100
200
500
1k
Hz
Sweep
Trace
Color
Line Style
Thick
Data
Axis
1
1
1
2
Blue
Red
Solid
Solid
3
3
Fft.Ch.1 Ampl
Fft.Ch.2 Ampl
Left
Left
THD (-1dBFS signal) FFT, Line Outputs
Comment
13
Output THD FFT.at27
2k
5k
10k
20k
-11
2
1
2
Red
Solid
3
Fft.Ch.2 Ampl
Left
1
THD (-1dBFS signal) FFT, Line Outputs
L
Output THD FFT.at27
Mbox Mini Input Frequency Response
AVID
Mbox Mini
AVID
+1
+0
-10
+0.8
-20
-30
+0.6
-40
+0.4
-50
-60
+0.2
d
B
r
d
B
F
S
+0
1
-0.2
-70
-80
-90
-100
-110
-0.4
-120
-0.6
-130
-140
-0.8
-150
-1
20
50
100
200
500
1k
2k
5k
10k
20k
-160
20
Hz
Sweep
Trace
Color
Line Style
Thick
Data
Axis
1
1
1
2
Blue
Red
Solid
Solid
3
3
DSP Anlr.Level A
DSP Anlr.Level B
Left
Left
Mbox Mini Output Frequency Response
AVID
Comment
S
1
1
Mbox Mini
Line Inputs, Min Gain
T
Input Freq Resp.at27
-9
-9.2
-9.4
-9.6
-9.8
d
B
u
-10
-10.2
-10.4
-10.6
-10.8
20k
-11
20
50
100
200
500
1k
Hz
Sweep
Trace
Color
Line Style
Thick
Data
Axis
1
1
1
2
Blue
Red
Solid
Solid
3
3
DSP Anlr.Level A
DSP Anlr.Level B
Left
Left
Line Outputs, -10dBu @1kHz
Comment
14
Output Freq Resp.at27
2k
5k
10k
20k
1
2
Red
Solid
3
DSP Anlr.Level B
Left
Line Outputs, -10dBu @1kHz
Output Freq Resp.at27
Mbox Mini Input THD
AVID
Mbox Mini
+0
-10
-20
-30
-40
-50
-60
-70
d
B
F
S
-80
-90
-100
-110
-120
-130
-140
-150
-160
20
20k
50
100
200
500
1k
2k
5k
10k
20k
Hz
Sweep
Trace
Color
Line Style
Thick
Data
Axis
1
1
1
2
Blue
Red
Solid
Solid
3
3
Fft.Ch.1 Ampl
Fft.Ch.2 Ampl
Left
Left
Mbox Mini Output THD
AVID
Comment
AVID
Mbox Mini
THD (-1dBFS signal) FFT, Line Inputs, Min Gain
THD FFT.at27
-9
+10
+0
-9.2
-10
-9.4
-20
-30
-9.6
-40
-9.8
-50
d
B
u
-60
d
B
u
-70
-80
-10
-10.2
-90
-10.4
-100
-110
-10.6
-120
-10.8
-130
-140
20
50
100
200
500
1k
2k
5k
10k
20k
-11
20
Hz
Sweep
Trace
Color
Line Style
Thick
Data
Axis
Comment
© 2011 Avid Technology, Inc.
Product
features, specifications,
system
requirements,
1 All rights
1 reserved.
Blue
Solid
3
Fft.Ch.1
Ampl
Left and availability are subject to change without notice. Avid, the Avid logo, Mbox, Pro Tools, and Pro Tools|HD
are trademarks or registered trademarks of Avid Technology, Inc. or its subsidiaries in the United States and/or other countries. All other trademarks contained herein are the property of their respective owners.
1
2
Red
Solid
THD (-1dBFS signal) FFT, Line Outputs
3
Fft.Ch.2 Ampl
Left
15
Output THD FFT.at27
S
1
1
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