Wheatstone AM-55 User manual

Digital auDio Processor
AM - 55
600 Industrial Drive, New Bern, North Carolina 28562 (tel [phone] / fax [phone] )
Technical
Manual

Technical
Manual
Wheatstone Corporation
September 2015
Digital auDio Processor
AM - 55

600 Industrial Drive
New Bern, North Carolina 28562
tel [phone] / fax [phone]
Wheatstone Digital Augio Processor Technical Manual
©2015 Wheatstone Corporation
AM-55 /Sep 2015
Ultra-HigH resolUtion Processing
ORSIS

IntroductIon - 1
AM-55 / Sep 2015
The History of Wheatstone Audio Processors
Introduced in 2005, the Vorsis product line evolved from Wheatstone’s return to
its original roots in audio processing. Having designed and integrated analog and
then, later, complex digital audio processing into our radio and television consoles
and control surfaces, Wheatstone was perfectly poised to address the challenges of
combining very high audio quality with competitive on air loudness.
Wheatstone audio processors are built to the same exacting standards as all
Wheatstone products. Research and development, manufacturing, testing, and quality
control for the line of audio processors are all accomplished within Wheatstone’s large
state‑of‑the‑art facility located in New Bern, North Carolina. Keeping everything
under one roof allows Wheatstone to have control over every facet of production
and ensures that our costumers receive products of the highest possible quality and
reliability. Staying true to “Made in the USA,” Wheatstone does not utilize offshore
manufacturing.
A dozen experts with deep experience in Digital Signal Processing, broadcast
audio and other engineering disciplines comprise our design team. Led by audio
processing expert and broadcast engineering veteran Jeff Keith, the team combines
their talents to design and build audio processors that achieve the highest standards
of on‑air sound quality.
In its short history Wheatstone Processing has already invented many new and
unique audio processing algorithms – algorithms that push audio processor performance
to new and higher levels. Wheatstone was the rst to develop an intelligent, “program
density aware” AGC (2007 - Sweet Spot Technology, or SST). We were also the rst
to employ the science of human psychoacoustics in the design of a multiband limiter
(2005, our acclaimed 31‑band limiter). In addition, our well‑regarded Bass Manage‑
ment systems solve the bass intermodulation problems that plague other brands of
audio processors when pushed for competitive loudness.
Each Wheatstone Processing product comes with its ownWindows®software‑based
intuitive Graphical User Interface for control of the processor. Carefully tuned factory
presets ensure that our audio processors can be placed into use quickly and easily in
any size market with a minimum of effort.
ORSIS
Ultra-HigH resolUtion Processing

page Contents – 1
AM-55 / Sep 2015
CONTENTS
AM‑55 Technical Manual
Chapter 1 ‑ General Information
Table of Contents
Introduction....................................................................................1‑2
AM‑55 Feature Overview...............................................................1‑3
Rack Mounting...............................................................................1‑3
AM-55 Installation Tips...............................................................................................1-4
Grounding...............................................................................................................1-4
Surge Protection.....................................................................................................1-4
UPS/Power Conditioning........................................................................................1-4
Analog Audio Input Connections ............................................................................1-4
Analog Audio Output Connections .........................................................................1-5
Digital Audio Connections ......................................................................................1-5
Where to Install the AM-55.........................................................................................1-6
Ratings Encoders ...................................................................................................1-6
Insert Point (Future Feature) ..................................................................................1-6
AC Power Considerations ............................................................1‑6
Rear Panel Connections ...............................................................1‑7
Audio Inputs................................................................................................................1-7
Analog In .................................................................................................................1-7
AES In .....................................................................................................................1-8
AM Audio Outputs ......................................................................................................1-8
TX Out .....................................................................................................................1-8
AES Out...................................................................................................................1-8
Headphone Monitoring ...............................................................................................1-8
Network Connection ...................................................................................................1-8
Ethernet RJ-45 ........................................................................................................1-9
Typical Straight-Through Cable...............................................................................1-9
Typical Crossover Cable .........................................................................................1-9
General Purpose Interface (GPIO)............................................................................1-10
GPIO RJ-45............................................................................................................1-11
Processing Presets....................................................................................................1-11
AM-55 Input/Output Connections Drawing................................................................1-13
Meters.............................................................................................2‑2
Input Level Meters......................................................................................................2-2
AGC Meters................................................................................................................2-2
Limiter Meters.............................................................................................................2-3
Output Meters.............................................................................................................2-3
OLED Display.................................................................................2‑3
Headphone.................................................................................................................2-5
Source Selection .....................................................................................................2-5
Headphone Volume.................................................................................................2-5
Chapter 2 ‑ AM‑55 Front Panel

page Contents – 2
AM-55 / Sep 2015
CONTENTS
Presets .......................................................................................................................2-5
Input............................................................................................................................2-5
Input Source ............................................................................................................2-5
Input Gain Adjustment.............................................................................................2-6
Pre-Emphasis.............................................................................................................2-6
Sound .........................................................................................................................2-6
Texture ....................................................................................................................2-6
EQ ...........................................................................................................................2-7
Save ........................................................................................................................2-7
A Note About The Front Panel Sound Adjustments ................................................2-7
Output.........................................................................................................................2-8
Network ......................................................................................................................2-9
Changing The Network Settings .............................................................................2-9
Leading Zeroes........................................................................................................2-9
Default IP Address...................................................................................................2-9
Vesions.......................................................................................................................2-9
Access.......................................................................................................................2-10
Getting Started...............................................................................3‑4
Connecting With the GUI ..............................................................3‑5
Configuring the GUI ......................................................................3‑5
Connecting Directly Without a LAN ............................................................................3-5
The AM-55 and Internet Security Concerns ...............................................................3-6
About DHCP and the AM-55 ......................................................................................3-6
The AM-55 Network Protocols and Ports Used..........................................................3-6
Using the AM‑55 GUI.....................................................................3‑7
Dynamic Displays Region...........................................................................................3-8
Frequency-Domain Graph.......................................................................................3-8
Managing the Blue Dots - Tutorial...........................................................................3-8
Control Area Region..................................................................................................3-10
Input Menu..............................................................................................................3-11
Input Source .......................................................................................................3-11
Input Signal Presence ........................................................................................3-11
Automatic Input Failover.....................................................................................3-12
Input Level Control .............................................................................................3-12
Input Polarity.......................................................................................................3-12
Phase Rotator.....................................................................................................3-12
HPF - High Pass Filter........................................................................................3-13
Metering..............................................................................................................3-13
Equalizer Menu.......................................................................................................3-14
Manipulating Equalization Curves via Mouse ....................................................3-15
EQ Enable ..........................................................................................................3-15
Multiband AGC-Leveller Menu ...............................................................................3-16
A Word About Outboard Processors and Rreeveettbb.......................................3-16
iAGC Controls.....................................................................................................3-18
Gate Threshold...............................................................................................3-18
iAGC Attack....................................................................................................3-18
iAGC Release.................................................................................................3-18
RTZ Enable ....................................................................................................3-18
Chapter 3 ‑ AM‑55 PC GUI

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AM-55 / Sep 2015
CONTENTS
RTZ Down ......................................................................................................3-18
RTZ Up...........................................................................................................3-18
Multiband Leveller Controls................................................................................3-18
AGC Drive ......................................................................................................3-18
Gate Delay......................................................................................................3-18
Leveller Gate Mode ........................................................................................3-19
Leveller Gate Threshold .................................................................................3-19
Crossover Frequencies ..................................................................................3-19
Band Coupling and Key Band ........................................................................3-19
Multiband Leveller Dynamic Displays Menu.......................................................3-20
Threshold........................................................................................................3-22
Leveller Attack................................................................................................3-22
Leveller Release.............................................................................................3-22
Density............................................................................................................3-22
Compressor Attack.........................................................................................3-22
Compressor Release......................................................................................3-23
Ratio ...............................................................................................................3-23
AGC Mix .........................................................................................................3-23
MB Limiter Menu ....................................................................................................3-24
Limiters and Clipper Controls .............................................................................3-24
Enable Limiters...............................................................................................3-24
Multiband Limiter Drive...................................................................................3-24
Limiter Knee ...................................................................................................3-25
Bass Clipper Threshold ..................................................................................3-25
Enable ............................................................................................................3-25
Bass Style 2....................................................................................................3-25
Filter Shape ....................................................................................................3-25
Boost ..............................................................................................................3-26
Main Clipper Drive..........................................................................................3-26
Pre-Emphasis.................................................................................................3-26
AM Diversity Delay .........................................................................................3-26
Limiters and Clipper Dynamic Displays Menu ....................................................3-27
Attack..............................................................................................................3-27
Release ..........................................................................................................3-27
Final Clipper And Output Menu ..............................................................................3-28
Test Oscillator.....................................................................................................3-28
Positive Peak Threshold.....................................................................................3-28
Output Bandwidth...............................................................................................3-29
Digital Output......................................................................................................3-29
TX Outputs .........................................................................................................3-29
Polarity Invert......................................................................................................3-29
LF Tilt EQ ..........................................................................................................3-30
Adjusting The LF Tilt EQ ...............................................................................3-30
HF Correction ....................................................................................................3-31
System Menu..........................................................................................................3-33
Input/Output Settings Change With Preset.........................................................3-33
Send Metering Data Over TCP/IP ......................................................................3-33
System Status ....................................................................................................3-34
Security...............................................................................................................3-34
Remote Login .................................................................................................3-34
Front Panel.....................................................................................................3-34
GUI Access.....................................................................................................3-35
GUI Lock.........................................................................................................3-35

page Contents – 4
AM-55 / Sep 2015
CONTENTS
Side Bar Region ........................................................................................................3-36
Preset List...............................................................................................................3-36
Preset Library .........................................................................................................3-36
Locking Presets..................................................................................................3-36
How to View Preset Changes.............................................................................3-37
Save Preset............................................................................................................3-37
Config. Devices ......................................................................................................3-38
Headphone Source.................................................................................................3-38
Headphone Control ................................................................................................3-38
Title Bar Region.........................................................................................................3-39
Status .....................................................................................................................3-39
Device.....................................................................................................................3-39
Current Preset ........................................................................................................3-39
Notes on Online and Offline Working .....................................................................3-40
Accessing Menu Options...........................................................................................3-41
File Menu Items......................................................................................................3-41
Hardware Menu Items ............................................................................................3-41
AM-55 Hardware Update....................................................................................3-41
Preset Menu Items .................................................................................................3-43
General Specifications..................................................................A‑3
Interpreting Common Audio Processing Terms.........................A‑8
Background ................................................................................................................A-8
Audio Terms and Wheatstone Processing .................................................................A-9
Thump/Rumble/Bottom............................................................................................A-9
Punch/Boom/Tubby/Warm .....................................................................................A-10
Mud.........................................................................................................................A-10
Honk .......................................................................................................................A-10
Whack.....................................................................................................................A-10
Fuzzy/Tinny ............................................................................................................A-11
Sibilance.................................................................................................................A-11
Treble/Bright/Open .................................................................................................A-11
Finally .....................................................................................................................A-12
WheatNet‑IP Configuration..........................................................A‑14
Adding AM-55 to The WheatNet-IP System..............................................................A-14
Appendix B
Appendix C
Appendices
Appendix A

page 1 – 1
FM-55 / Aug 2014
GENERAL INFORMATION
General Information
Introduction....................................................................................1-2
AM-55 Feature Overview...............................................................1-3
Rack Mounting...............................................................................1-3
AM-55 Installation Tips...............................................................................................1-4
Grounding...............................................................................................................1-4
Surge Protection.....................................................................................................1-4
UPS/Power Conditioning .......................................................................................1-4
Analog Audio Input Connections............................................................................1-4
Analog Audio Output Connections.........................................................................1-5
Digital Audio Connections......................................................................................1-5
Where to Install the AM-55.........................................................................................1-6
Ratings Encoders ...................................................................................................1-6
Insert Point (Future Feature) ...................................................................................1-6
AC Power Considerations ............................................................1-6
Rear Panel Connections ...............................................................1-7
Audio Inputs ...............................................................................................................1-7
Analog In .................................................................................................................1-7
AES In......................................................................................................................1-8
AM Audio Outputs......................................................................................................1-8
TX Out .....................................................................................................................1-8
AES Out...................................................................................................................1-8
Headphone Monitoring...............................................................................................1-8
Network Connection ..................................................................................................1-8
Ethernet RJ-45 ........................................................................................................1-9
Typical Straight-Through Cable...............................................................................1-9
Typical Crossover Cable..........................................................................................1-9
General Purpose Interface (GPIO).............................................................................1-10
GPIO RJ-45 ............................................................................................................1-11
Processing Presets....................................................................................................1-11
AM-55 Input/Output Connections Drawing...............................................................1-13
Chapter Contents

page 1 – 2
FM-55 / Aug 2014
GENERAL INFORMATION
General Information
Introduction
Welcome to the Wheatstone AM-55 Digital Audio Processor. The AM-55 has been
carefully designed to deliver a clean and easy to listen to sound on the dial along with
very competitive loudness when that is the goal. The AM-55 expands on technologies
previously invented by Wheatstone, incorporates several new ones, and delivers that
“sought after” sound no matter what the market size. Like other Wheatstone processors,
the AM-55 has been carefully designed to not have a xed sound of its own – the end
user can use the AM-55’s vast pallet of tools to create any desired on-air sound.
TheAM-55’s processing algorithms have been carefully evaluated though many hours
of critical listening with a very wide range of program material. The AM-55’s processing
algorithms deliver amazingly clean, clear, and if desired, loud, on-air sound. Music sounds
like it was meant to sound. Voices are rich and full and without unnatural coloration or
distortion. Transitions between widely varying program elements are deftly handled, and
if desired, with no trace of “processing” during spectral balance and density corrections.
Remote control of theAM-55 is via a Windows-based Graphical User Interface (GUI)
software and can be accomplished via 100BaseT wired Ethernet. Up to four simultaneous
remote control sessions are possible. General Purpose Input/Output is provided on an
RJ-45 to interface to station systems.
The AM-55 utilizes an internal base sampling rate of 192 kHz. Higher sample rates
are used where it is benecial to do so, such as within the AM-55 clipper. A 24-bit, 144dB
internal dynamic range signal path allows audio to be processed with extreme precision.
The front panel OLED screen permits convenient control of system and basic processing
setup parameters and sound controls.
Those wishing for remote or PC control over all parameters will appreciate our
full-control GUI.This GUI is available free of charge and comes on a CD thataccompanies
this product or can be downloaded at http://wheatstone-processing.com.
Wheatstone products are designed and manufactured in our Corporate Headquarters
in New Bern, North Carolina, USA. This large, state-of-the-art facility affords complete
control over product quality during every step of the design and manufacturing process.
In order to maintain the high product quality that Wheatstone has been known for, no
offshore manufacturing is utilized.
The following pages will help you get theAM-55 up and running as quickly as possible
without having to know a lot of techie stuff.
If during installation or setup you nd that you need assistance or advice, please feel
free to contact our technical support folks at [phone] or email us at: techsupport@
wheatstone.com.

page 1 – 3
FM-55 / Aug 2014
GENERAL INFORMATION
AM-55 Feature Overview
The AM-55 Audio Processor has been designed to process audio for conventional
analog AM.
Input audio can be analog or digital, with options on the digital input via WheatNet-IP
or standard AES-3 connection. And input failover between the digital or analog inputs is
available.
Processing blocks include a phase rotator and high pass lter, a four band equalizer,
ve band iAGC processor and a ve band limiter.
The nal stage of the signal path utilizes a new clipper technology unique to the AM‑55.
Several dozen factory presets are provided with the AM‑55, making a very wide
range of on air sounds and textures available to the user right out of the box. When used
in combination with the front panel’s Audio Processing controls each factory preset offers
over a million different on‑air sounds to the user.
The AM‑55 is also equipped with Wheatstone’s ACI protocol, allowing complete control
of not only presets, but any parameter that is assigned to a user control (please contact the
factory for details on using this feature).
Rack Mounting
The AM‑55 is designed to t into an industry standard 19" equipment rack, and requires
one rack unit (1.75") of vertical space. The unit has a depth of 9" behind the rack rails (in-
cluding chassis connectors), and its chassis has a width of 17‑11/32". Space needed in front
of rack rails is 3/4" and an additional ve inches of space is required for wiring cables to
pass through. If using only two rack screws always use the bottom two screws to prevent
twisting of the front panel and other undue forces from harming the processor chassis.
The AM‑55 may be mounted between other devices in the equipment rack; however, in
accordance with good engineering practice it should not be mounted directly above devices
that generate a signicant amount of heat (such as power ampliers or power supplies). If
such a location is unavoidable, then it is advisable to utilize an extra 1RU blank rack panel
between the AM‑55 and devices imm ediately above and/or below it.
WARNING!
With very few exceptions, the AM-55 chassis DOES NOT need to be opened in the
eld.
Please be advised that the AM‑55 contains high voltage power supply circuits
operating at voltages well above AC line input.
These voltages are hazardous and potentially deadly if accidentally contacted.
Special tools, software, and xtures are required for service. There are no
user‑serviceable parts inside.
The AM‑55 unit must be returned to Wheatstone Corporation under a Return
Authorization in the unlikely event that repair is necessary.
If you need to return the AM‑55 to Wheatstone for repair, please contact our
ofce at 252-638-7000 Monday – Friday 8:30am to 5:30pm ET or after hours at
[email protected] for a Return Authorization (RA) number.

page 1 – 4
FM-55 / Aug 2014
GENERAL INFORMATION
AM-55 Installation Tips
Grounding
Establish a low impedance common ground in the facility and try to route all
equipment grounds to that point. Use ground conductors with the largest possible
surface area and keep ground leads as short as possible. TheAM-55’s ground reference
is its chassis, which should be connected to the station ground. Such a connection is
especially important when the AM-55 is operated in a high RF environment because it
helps minimize differential voltages between the processor’s chassis and other pieces
of equipment such as the rack it is mounted within.
Surge Protection
Always place surge protection circuits as close as possible to the device being
protected. AC power line surge protection should manage transients in a way that keeps
instantaneous potential differences between the power line hot, neutral,AC grounding
conductor, the station ground, and the processor chassis as low as possible. Likewise,
measures should also be taken to keep the instantaneous potential difference between
the audio cable shields and the processor chassis as low as possible (this applies to
all audio equipment, not just the AM-55), particularly when the equipment is located
within the electrically hostile environment of a station’s transmitter facility.
UPS/Power Conditioning
Choose the best power conditioning/UPS units that your budget will allow, focusing
on the most important features and options that you actually need. Some questions to
ask while reviewing features are:
- How does the UPS behave when AC power is not exactly 60Hz, such as when
the facility is on its backup generator?
- If the UPS has onboard surge protection, what kind of surge capability does it
have and where are those surges directed to?
- Is the UPS equipped with remote monitoring capability?
- Does the UPS have onboard monitoring and alarms to signal problems such as
low batteries?
Analog Audio Input Connections
Balanced audio input sources should be connected to the AM-55 using standard
two-conductor shielded audio cable such as Belden 8451 or 9451.
Unbalanced input audio connections
should be made with shielded two
conductor cable. At the unbalanced
source’s output connect the “+” output
to AM-55’s “Hi” input (XLR pin 2) and
connect the shield wire to the AM-55’s
“Lo” input (XLR pin 3). If the cable’s
shield is used (recommended) connect it
at the AM-55 end only (XLR pin 1) to
prevent AC ground loops.

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FM-55 / Aug 2014
GENERAL INFORMATION
If RF interference is an issue, the far (oating
and ungrounded) end of an audio cable
shield can be experimentally bypassed to
RF ground via a 0.01µF, 250V AC rated
capacitor. Suitable capacitors are:
TDK CS17-F2GA103MYGS
Murata DE2F3KH103MA3B
Panasonic ECK-ATS103MF
AVX 65N103MBLCP
Analog Audio Output Connections
Balanced audio loads are recommended and should be connected to the AM-55’s
outputs using standard two-conductor shielded audio cable. Unbalanced audio loads
should be avoided, but if they can’t they should be connected using shielded two conduc-
tor cable such as Belden 8451 or 9451 (as if connecting a balanced source).
TheAM-55 is equipped with active balanced output stage that behaves like a transformer.
Because of this behavior the correct wiring method may be different than expected.
The unbalanced load’s “Hi” lead should be
connected to XLR connector Pin
2 (“Hi”).
The unbalanced load’s shield should be
connected to the AM-55’s output XLR Pin 3
(“Lo”). Then, and to enable the AM-55’s
balanced output amplier to operate correctly when driving the unbalanced load, it is
recommended that the AM-55’s XLR output Pin 1 (ground/shield) also be connected to
Pin 3 (“Lo”), noting that this MUST BE DONE at the AM-55’s output connector (see
the diagram above).
Note that it is not advisable to connect Pin 1 and Pin 3 conductors together at the far
end of the cable. Doing so can induce external noise and crosstalk on the output amplier’s
“load sense” lead which is XLR Pin 3 when Pin 2 is being used as the “Hot.”
As in the input case, if RF interference is
an issue the far (oating) end of the cable
shield can be experimentally bypassed to
RF ground through a 0.01µF 250V AC
rated capacitor to see if it helps. Please
refer to the listing above for capacitors
known to be suitable for this task.
Digital Audio Connections
For digital audio connections always use a good quality digital audio cable (or twisted
pair Category 5E/6 Network cable) having a characteristic impedance of 110 ohms. This
cable should be shielded where possible, and in the case of multi-pair cable, each pair
should be individually shielded. Foil shielding is recommended for permanent installations,
and a cable with foil shield plus an overall braid should be used in applications where
frequent exing of cables might occur.

page 1 – 6
FM-55 / Aug 2014
GENERAL INFORMATION
Generic “audio” cable such as Belden 8451 and 9451 may sometimes be used for inter-
connectingAES3 digital audio devices as long as the cable is short. The actual cable length
that will work satisfactorily is determined by many factors including the error correction
and jitter tolerance of the AES3 receiver, the characteristics of the digital cable driver and
the characteristics of the specic cable being used and its length. “Generic” analog audio
cables usually have higher capacitance than digital cable and high capacitance cables can
impair the ability of theAES3 receiver to recover the digital signal without errors. Increased
jitter, dropouts, or no audio at all can be an indication of an improper cable type.
Where to Install the AM-55
The best and really the ONLY location to install the AM-55 is at the transmitter site.
The major benet of a transmitter site installation is that it allows much tighter control of
modulation peaks.
A transmitter site location has the additional benet of allowing the use of the AM-55’s
peak processing and asymmetry control to provide maximum modulation control and loud-
ness to your AM signal. The use of the AM-55 in any location other than the transmitter
site is not recommended as the AM-55 was designed to be the very last piece of processing
gear prior to the transmitter.
Ratings Encoders
Field experience has been that Wheatstone audio processors favorably pass the data
watermarking scheme used in the rating service technology, regardless of the aggressive-
ness of the processing being performed.
Insert Point (Future Feature)
For those concerned with the survivability of the ratings encoder watermark, the
AM-55 does have a ratings encoder insert point that places the encoder towards the back
of the audio processor just before the nal peak controller. This allows the AM-55 AGC/
Compressor and Limiter to provide a consistent audio signal to the encoder to improve
watermark robustness and encoding reliability.
AC Power Considerations
Please note that in order to enhance its long-term reliability, the AM-55 has no power
switch because all power switches notoriously become intermittent over time without
regular use.
The AM-55 accepts AC line input voltages between 90 and 260 VAC, 50 or 60Hz.
Power consumption is under 100VA.
Although aggressive AC input ltering is utilized on the AC power input it is always
advisable to use external surge protection and an uninterruptible power supply (UPS)
wherever possible, especially where the AC power quality can be in question, such as at
a remote transmitter site.
Power conditioning, surge suppression, and even power backup devices are wise invest-
ments when using sensitive modern electronic devices. The AM-55 is, after all, a highly
specialized “computer.”
The use of a UPS as recommended will protect the AM-55 from short duration power
interruptions and glitches which might otherwise signal it to reboot. When the AM-55
reboots there will be a loss of audio for approximately 15 seconds.

page 1 – 7
FM-55 / Aug 2014
GENERAL INFORMATION
Rear Panel Connections
The image below shows the rear panel of the AM-55 and the location of various
connectors associated with an installation
Audio Inputs
The AM-55 accepts three types of audio input sources:
• Balanced analog line level left/right audio;
• Digital AES3 compliant left/right audio with sample rates between 32kHz and 96kHz;
• WheatNet-IP via 100BaseT Ethernet connection to a WheatNet-IP audio network.
Input audio can be applied to any or all inputs simultaneously with the caveat that
the WheatNet-IP input and AES3 inputs share a common digital path into the internal
processing.
Automatic audio failover from analog to digital or vice versa is supported. Automatic
failover from AES3 or WheatNet-IP to analog is instantaneous and based on invalid or
missing bits in the AES3 or WheatNet-IP stream, or after 30 seconds of “silence” (level
below -42dBFS).
Automatic failover from analog to AES3 or WheatNet-IP is based on silence sense
responding to audio being below -42dBFS for more than 30 seconds.
Failover capability is not available between the AES and WheatNet-IP inputs.
Analog In – XLR-F
Pin 1 XLR LT SH – LINE LT IN SH
Pin 2 XLR LT HI – LINE LT IN HI
Pin 3 XLR LT LO – LINE LT IN LO
CONNECTOR TYPE FUNCTION & NOTES
1 XLR Female Left Analog Input
2 XLR Female Right Analog Input
3 XLR Male TX Output #1
4 XLR Male TX Output #12
5 XLR Female AES Audio Input
6 XLR Male AES Audio Output
7 RJ-45 GPI Interface
8 RJ-45 Ethernet (Network) Connection / WheatNet-IP audio connection
9 IEC Mains connection (90-240~VAC / 50-60Hz)
AM‑55 Rear Panel Connections (left to right)

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FM-55 / Aug 2014
GENERAL INFORMATION
Pin 1 XLR RT SH – LINE RT IN SH
Pin 2 XLR RT HI – LINE RT IN HI
Pin 3 XLR RT LO – LINE RT IN LO
AES In – XLR-F
Pin 1 XLR SH – AES IN SH
Pin 2 XLR HI – AES IN HI
Pin 3 XLR LO – AES IN LO
AM Audio Outputs
Output audio for the AM path is available as:
• Balanced analog mono (TX1 or TX2), bandwidth limited and pre-emphasized.
• AES3 digital mono (TX1 or TX2), bandwidth limited and pre-emphasized.
• WheatNet-IP audio network.
TX Out – XLR-M
Pin 1 XLR 1 SH – TX 1 OUT SH
Pin 2 XLR 1 HI – TX 1 OUT HI
Pin 3 XLR 1 LO – TX 1 OUT LO
Pin 1 XLR 2 SH – TX 2 OUT SH
Pin 2 XLR 2 HI – TX 2 OUT HI
Pin 3 XLR 2 LO – TX 2 OUT LO
AES Out – XLR-M
Pin 1 XLR SH – AES OUT SH
Pin 2 XLR HI – AES OUT HI
Pin 3 XLR LO – AES OUT LO
Headphone Monitoring
An overload protected stereo headphone amplier drives the front panel ¼" stereo
headphone output located on the left side of the AM-55’s front panel. The audio source
feeding the headphones may be chosen from the AM output or the analog and digital
inputs, even if those inputs have not been selected to feed the audio processing chain.
The System menu of the GUI hosts the headphone router selector as does the front panel
interface.
Network Connection
The AM-55 can connect to a network or PC/laptop over Wired Ethernet via the
100Base-T Ethernet port on the rear panel. This port is completely independent andAuto-
MDIX, allowing it to support straight-through and crossover cables in any combination.
The wired Ethernet interface can support up to four simultaneous connections to remote
GUIs.
For typical CAT5 cable pinouts see below. These connections are for communicating
with the conguration computer via a network.

page 1 – 9
FM-55 / Aug 2014
GENERAL INFORMATION
Ethernet – RJ-45
Pin 1 – TXD +
Pin 2 – TXD -
Pin 3 – RXD +
Pin 4 – N/C
Pin 5 – N/C
Pin 6 – RXD -
Pin 7 – N/C
Pin 8 – N/C
Typical Straight -Through Cable
Typical Crossover Cable
1
2
3
4
TXD +
TXD -
RXD +
RXD -
PIN
1
2
3
4
PIN
RJ-45
Plug RJ-45
Plug
White/Orange
5
6
7
8
N/
C
N/
C
5
6
7
8
Orange
White/Green
Blue
White/Blue
Green
White/Brown
Brown
N/
C
N/
C
White/Orange
Orange
White/Green
Blue
White/Blue
Green
White/Brown
Brown
1
2
3
4
TXD +
TXD -
RXD +
RXD -
PIN
1
2
3
4
PIN
RJ-45
Plug RJ-45
Plug
White/Orange
5
6
7
8
N/
C
N/
C
5
6
7
8
Orange
White/Green
Blue
White/Blue
Green
White/Brown
Brown
White/Green
Green
White/Orange
Blue
White/Blue
Orange
White/Brown
Brown
N/
C
N/
C
RXD +
RXD -
TXD +
TXD -
N/
C
N/
C
N/
C
N/
C

page 1 – 10
FM-55 / Aug 2014
GENERAL INFORMATION
General Purpose Interface (GPIO)
The AM-55 is equipped with two General Purpose input (GPI) and output (GPO) ports
on the rear RJ-45 connector. The General Purpose connections are optically-isolated from
AM-55’s internal circuitry to prevent external ground loops and to prevent dangerous
voltages from being introduced into AM-55.
• GP Input #1 – Forces Analog Input regardless of currently selected input.
• GP Input #2 – Forces Digital Input regardless of currently selected input.
• GP Output #1 – Analog Input is selected.
• GP Output #2 – Digital Input is selected.
Each of the General Purpose inputs is current limited by 475 Ohm internal resistance.
The LED device inside the opto-isolators is rated at a maximum forward current of 50mA
and a normal operating current of 5mA.
APPLIED VOLTAGE TO GPI EXTERNAL RESISTANCE
3.3 Volts None
5.0 Volts 330 Ohms
6.0 Volts 470 Ohms
7.5 Volts 820 Ohms
10.0 Volts 1.3 kOhms
12.0 Volts 1.8 kOhms
12.0 Volts 2.4 kOhms
24.0 Volts 3.9 kOhms
30.0 Volts 5.1 kOhms
*48.0 Volts* 9.1 kOhms
Before connecting external circuitry to the General Interface inputs,
rst ascertain whether it will be necessary to utilize additional outboard
series resistance in your application!
Use the following table to determine if an external resistance is required and if so, what
value it should be. Note that a one-half watt resistor is sufcient. The resistance values in
the table below have been calculated to result in approximately 5.0 milliamperes forward
current through the opto-isolator’s internal LED.
* For personal safety reasons a voltage in excess of 48VDC is
NOT recommended to be applied to the General Purpose inputs.
The opto-isolators on the General Purpose outputs protect internal AM-55 circuitry
from voltage up to 350 volts AC or DC. The MAXIMUM permissible load current is
100 milliamperes (0.10 Amperes).

page 1 – 11
FM-55 / Aug 2014
GENERAL INFORMATION
GPIO - RJ-45
The pin assignment for the rear panel RJ-45 GPI connector is as follows:
Pin 1 – GPI I IN +
Pin 2 – GPI 1 IN -
Pin 3 – GPI 2 IN +
Pin 4 – GPI 2 IN -
Pin 5 – GPI 1 OUT +
Pin 6 – GPI 1 OUT -
Pin 7 – GPI 2 OUT +
Pin 8 – GPI 2 OUT -
Processing Presets
The AM-55 comes equipped with several dozen factory presets and can hold a total
of 80 presets in its onboard memory. Customer-created presets may be saved within the
AM-55’s onboard memory until all preset storage slots are full. An unlimited number
of presets can be stored on the PC that hosts the Windows-based remote control GUI
software.
In order to prevent annoying clicks and pops when changing presets, preset parameters
are slewed between the current values and the new values whenever a new preset is
taken, and it may take several seconds for the new settings to completely settle in. It is
important to remember this concept!
The AM-55’s preset behavior is purposely designed to make preset changes as
unobtrusive as possible and therefore parameter changes are not instantaneous, but
gracefully take place over a matter of seconds. This factor must be taken into consideration
whenever switching back and forth between presets in order to compare them!
When a preset has been recalled and has not been modied the preset’s name is
displayed in green text within the GUI’s current preset window. If changes to the preset
have been made its name will be displayed in red text instead of green. Once the modi-
ed settings have been saved back to the AM-55’s hardware the preset name will again
be displayed in green.
Factory presets can be re-tuned and saved as new preset names in order to create a
completely different air sound. The factory presets are write-protected and changes made
to them cannot be written back to the same memory location. Factory presets that have
been modied are considered by the system to be “user” presets and therefore must be
saved as a new name and in a new preset storage slot.
Our advice is to start with a factory preset that has the on air sound that is closest
to what you believe you need. If changes are necessary, the best approach is to make
small changes, one or two at a time, and then listen for quite a while before deciding
that more changes are necessary. A consultant friend of ours advises: “Tweak small and
then listen large.”
NOTE:
Preset storage is as follows:
- Factory presets are installed beginning with a BYPASS stored in slot #1. Factory
presets cannot be written over or deleted.

page 1 – 12
FM-55 / Aug 2014
GENERAL INFORMATION
- User presets are stored above the highest-numbered factory preset. The number
of available slots for user presets depends on how many factory presets were
installed, which can vary with software version. The total number of presets on
the AM-55’s hardware cannot exceed eighty (80). The storage space available
for presets on the GUI’s host PC (because of a preset’s tiny le size) is virtually
unlimited.
- User presets may be locked at the user’s discretion to prevent inadvertent changes.
Any user can unlock user-locked presets.