dbx AFS224 User Manual

™

AFS

Dual Channel Advanced Feedback Suppression Processor

224

User Manual

IMPORTANT SAFETY INSTRUCTIONS

WARNING FOR YOUR PROTECTION

READ THE FOLLOWING:

KEEP THESE INSTRUCTIONS

HEED ALL WARNINGS

The symbols shown above are internationally accepted symbols that warn of
potential hazards with electrical products. The lightning flash with arrowpoint in
an equilateral triangle means that there are dangerous voltages present within
the unit. The exclamation point in an equilateral triangle indicates that it is
necessary for the user to refer to the owner’s manual.

These symbols warn that there are no user serviceable parts inside the unit.
Do not open the unit. Do not attempt to service the unit yourself. Refer all
servicing to qualified personnel. Opening the chassis for any reason will void
the manufacturer’s warranty. Do not get the unit wet. If liquid is spilled on the
unit, shut it off immediately and take it to a dealer for service. Disconnect the
unit during storms to prevent damage.

SAFETY INSTRUCTIONS

NOTICE FOR CUSTOMERS IF YOUR UNIT IS EQUIPPED WITH A POWER CORD.

WARNING: THIS APPLIANCE SHALL BE CONNECTED TO A MAINS SOCKET OUTLET WITH A PROTECTIVE
EARTHING CONNECTION.

THE CORES IN THE MAINS LEAD ARE COLOURED IN ACCORDANCE WITH THE FOLLOWING CODE:

GREEN AND YELLOW - EARTH BLUE - NEUTRAL BROWN - LIVE

AS COLOURS OF THE CORES IN THE MAINS LEAD OF THIS APPLIANCE MAY NOT CORRESPOND WITH
THE COLOURED MARKINGS IDENTIFYING THE TERMINALS IN YOUR PLUG, PROCEED AS FOLLOWS:

FOLLOW ALL INSTRUCTIONS

the apparatus shall not be exposed to dripping or splashing liquid and no object filled
with liquid, such as vases, shall be placed on the apparatus.

CLEAN ONLY WITH A DRY CLOTH.

DO NOT BLOCK ANY OF THE VENTILATION OPENINGS. INSTALL IN ACCORDANCE WITH
THE MANUFACTURER’S INSTRUCTIONS.

DO NOT INSTALL NEAR ANY HEAT SOURCES SUCH AS RADIATORS, HEAT REGISTERS,
STOVES, OR OTHER APPARATUS (INCLUDING AMPLIFIERS) THAT PRODUCE HEAT.

ONLY USE ATTACHMENTS/ACCESSORIES SPECIFIED BY THE MANUFACTURER.

UNPLUG THIS APPARATUS DURING LIGHTNING STORMS OR WHEN UNUSED FOR LONG
PERIODS OF TIME.

Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized
plug has two blades with one wider than the other. A grounding type plug has two
blades and a third grounding prong. The wide blade or third prong are provided for your
safety. If the provided plug does not fit your outlet, consult an electrician for replace­ment of the obsolete outlet.

Protect the power cord from being walked on or pinched particularly at plugs, conve­nience receptacles, and the point where they exit from the apparatus.

Use only with the cart stand, tripod bracket, or table specified by the manufacture,
or sold with the apparatus. When a cart is used, use caution when moving the cart/
apparatus combination to avoid injury from tip-over.

• THE CORE WHICH IS COLOURED GREEN AND YELLOW MUST BE CONNECTED TO THE TERMINAL
IN THE PLUG MARKED WITH THE LETTER E, OR WITH THE EARTH SYMBOL, OR COLOURED GREEN,
OR GREEN AND YELLOW.

• THE CORE WHICH IS COLOURED BLUE MUST BE CONNECTED TO THE TERMINAL MARKED N OR
COLOURED BLACK.

• THE CORE WHICH IS COLOURED BROWN MUST BE CONNECTED TO THE TERMINAL MARKED L OR

COLOURED RED.

THIS EQUIPMENT MAY REQUIRE THE USE OF A DIFFERENT LINE CORD, ATTACHMENT PLUG, OR BOTH,
DEPENDING ON THE AVAILABLE POWER SOURCE AT INSTALLATION. IF THE ATTACHMENT PLUG NEEDS
TO BE CHANGED, REFER SERVICING TO QUALIFIED SERVICE PERSONNEL WHO SHOULD REFER TO THE
TABLE BELOW. THE GREEN/YELLOW WIRE SHALL BE CONNECTED DIRECTLY TO THE UNITS CHASSIS.

CONDUCTOR

L LIVE BROWN BLACK

N NEUTRAL BLUE WHITE

E EARTH GND GREEN/YEL GREEN

WARNING: IF THE GROUND IS DEFEATED, CERTAIN FAULT CONDITIONS IN THE UNIT OR IN THE
SYSTEM TO WHICH IT IS CONNECTED CAN RESULT IN FULL LINE VOLTAGE BETWEEN CHASSIS AND
EARTH GROUND. SEVERE INJURY OR DEATH CAN THEN RESULT IF THE CHASSIS AND EARTH GROUND
ARE TOUCHED SIMULTANEOUSLY.

WIRE COLOR

Normal Alt

Refer all servicing to to qualified service personnel. Servicing is required when the ap­paratus has been damaged in any way, such as power-supply cord or plug is damaged,
liquid has been spilled or objects have fallen into the apparatus, the apparatus has been
exposed to rain or moisture, does not operate normally, or has been dropped.

POWER ON/OFF SWITCH: The Power switch used in this piece of equipment DOES NOT
break the connection from the mains.

MAINS DISCONNECT: The plug shall remain readily operable. For rack-mount or instal­lation where plug is not accessible, an all-pole mains switch with a contact separation
of at least 3 mm in each pole shall be incorporated into the electrical installation of the
rack or building.

If connected to 240V supply, a suitable CSA/UL certified power cord shall be used for
this supply.

This Equipment is intended for rack mount use only.

IMPORTANT SAFETY INSTRUCTIONS

ELECTROMAGNETIC COMPATIBILITY

This device complies with part 15 of the FCC Rules and the Prod­uct Specifications noted on the Declaration of Conformity.
Operation is subject to the following two conditions:

• this device may not cause harmful interference, and

• this device must accept any interference received, including

interference that may cause undesired operation.

Operation of this unit within significant electromagnetic fields
should be avoided.

• use only shielded interconnecting cables.

U.K. MAINS PLUG WARNING

A molded mains plug that has been cut off from the cord is
unsafe. Discard the mains plug at a suitable disposal facility.

NEVER UNDER ANY CIRCUMSTANCES SHOULD
YOU INSERT A DAMAGED OR CUT MAINS PLUG
INTO A 13 AMP POWER SOCKET.

Do not use the mains plug without the fuse cover in place.
Replacement fuse covers can be obtained from your local retailer.
Replacement fuses are 13 amps and MUST be ASTA approved to
BS1362.

If you want to dispose this product, do n ot mix it with general househo ld waste. There is a
separate collection system for used electronic products in accordance with legislation that
requires proper treatment, recovery and recycling.

Private household in the 25 member states of the EU, in Switzerland and Norway may return their used
electronic products free of charge to designated collection facilities or to a retailer (if you purchase a similar
new one).

For Countries not mentioned above, please contact your local authorities for a correct method of disposal.

By doing so you will ensure that your disposed product undergoes the necessary treatment, recovery and
recycling and thus prevent potential negative effects on the environment and human health.

DECLARATION OF CONFORMITY

Manufacturer’s Name: dbx Professional Products
Manufacturer’s Address: 8760 S. Sandy Parkway
Sandy, Utah 84070, USA
declares that the product:

Product name: dbx AFS224
Note: Product name may be suffixed by the EU.

Product option: None

conforms to the following Product Specifications:

Safety: IEC 60065 -01+Amd 1

EMC: EN 55022:2006
EN 55024:1998
FCC Part 15

Supplementary Information:

The product herewith complies with the requirements of the:
Low Voltage Directive 2006/95/EC
EMC Directive 2004/108/EC.
RoHS Directive 2002/95/EC
WEEE Directive 2002/96/EC

With regard to Directive 2005/32/EC and EC Regulation 1275/2008
of 17 December 2008, this product is designed, produced, and
classified as Professional Audio Equipment and thus is exempt from this
Directive.

Roger Johnsen
Director, Engineering
Signal Processing
8760 S. Sandy Parkway
Sandy, Utah 84070, USA
Date: May 31, 2012

European Contact: Your local dbx Sales and Service Office or

Harman Signal Processing
8760 South Sandy Parkway
Sandy, Utah
84070 USA
Ph: [phone]
Fax: [phone]

Service / Warranty

AFS™ 224

Service Contact Info

If you require technical support, contact dbx Technical Support. Be prepared to accurately describe the
problem. Know the serial number of your device - this is printed on a sticker attached to the chassis. If you
have not already taken the time to fill out your warranty registration card and send it in, please do so now.
You may also register online at www.dbxpro.com.

Before you return a product to the factory for service, we recommend you refer to the manual. Make sure
you have correctly followed installation steps and operation procedures. For further technical assistance
or service, please contact our Technical Support Department at [phone] or visit www.dbxpro.com.
If you need to return a product to the factory for service, you MUST first contact Technical Support to
obtain a Return Authorization Number.

No returned products will be accepted at the factory without a Return Authorization Number.

Please refer to the Warranty information on the following page, which extends to the first end-user. After
expiration of the warranty, a reasonable charge will be made for parts, labor, and packing if you choose to
use the factory service facility. In all cases, you are responsible for transportation charges to the factory.
dbx will pay return shipping if the unit is still under warranty.

Use the original packing material if it is available. Mark the package with the name of the shipper and with
these words in red: DELICATE INSTRUMENT, FRAGILE! Insure the package properly. Ship prepaid,
not collect. Do not ship parcel post.

Warranty

1. The warranty registration card that accompanies this product must be mailed within 30 days after
purchase date to validate this warranty. You can also register online at www.dbxpro.com. Proof-of­purchase is considered to be the responsibility of the consumer. A copy of the original purchase receipt
must be provided for any warranty service.

2. dbx warrants this product, when purchased new from an authorized U.S. dbx dealer and used solely
within the U.S., to be free from defects in materials and workmanship under normal use and service.
This warranty is valid to the original purchaser only and is non-transferable.

3. dbx liability under this warranty is limited to repairing or, at our discretion, replacing defective
materials that show evidence of defect, provided the product is returned to dbx WITH RETURN
AUTHORIZATION from the factory, where all parts and labor will be covered up to a period of two
years. A Return Authorization number must first be obtained from dbx. The company shall not be liable
for any consequential damage as a result of the product’s use in any circuit or assembly.

4. dbx reserves the right to make changes in design or make additions to or improvements upon this
product without incurring any obligation to install the same additions or improvements on products
previously manufactured.

5. The foregoing is in lieu of all other warranties, expressed or implied, and dbx neither assumes nor
authorizes any person to assume on its behalf any obligation or liability in connection with the sale of
this product. In no event shall dbx or its dealers be liable for special or consequential damages or from
any delay in the performance of this warranty due to causes beyond their control.

Service / Warranty

AFS™ 224 User Manual

AFS™ 224

Table of Contents

Introduction

Defining the AFS 224 .......................................................................................................................................2

Installation Recommendations .........................................................................................................................3

Connection Recommendations ........................................................................................................................3

Front & Rear Panels

Front Panel ..........................................................................................................................................................4

Rear Panel ............................................................................................................................................................5

Applications

System Connection & Gain Structure ............................................................................................................6

Application 1 – Mixer Channel Inserts ..........................................................................................................7

Application 2 – Mixer Subgroup Inserts ........................................................................................................8

Application 3 – Mixer Master Stereo Output Inserts ..................................................................................9

Application 4 – In-line Between Mixer & Amp .........................................................................................10

Operation

Quick Start ........................................................................................................................................................11

Setup Mode .......................................................................................................................................................12

Fixed Mode .......................................................................................................................................................14

Live Mode ..........................................................................................................................................................15

Other Functions ...............................................................................................................................................16

Clearing Filters ........................................................................................................................................16

Front Panel Lockout ..............................................................................................................................16

Linking Channels ....................................................................................................................................16

Technical Information

Factory Hard Reset ..........................................................................................................................................17

Block Diagram ..................................................................................................................................................18

Specifications ....................................................................................................................................................19

AFS™ 224 User Manual

Table of Contents

Introduction

Congratulations on your purchase of the dbx AFS™ 224. The AFS 224 Advanced Feedback Suppression
processor was designed to provide state-of-the-art feedback elimination processing, while maintaining a
simple and intuitive control interface. From the powerful DSP module to the no-nonsense user interface,
the AFS 224 provides all the processing and control necessary for both installation and live use. The AFS
224 is an absolute must for any live sound application.

Ten and twelve filter feedback elimination processors have become the de facto standard, but the
engineering staff at dbx have never been content residing in the neighborhood of the status quo. So, to
raise the bar once again, we went out and developed a dedicated feedback suppression processor that
offers up to 24 filters per channel with widths as narrow as 1/80 of an octave. To achieve these staggering
numbers, we utilized our patent-pending AFS™ technology, which had previously only been available in
the upper echelon line of products. In addition to the plethora of feedback suppression filters available, the
AFS 224 also offers selectable filter widths, “Fixed” and “Live” filter types for static and dynamic filtering,
Live Filter Lift with selectable lift times, and dual mono or stereo operation, all readily available via the
front panel’s intuitive user interface. This manual will be your guide to understanding the full functionality
of the powerful AFS 224 processor.

AFS™ 224

Defining the AFS 224

The dbx AFS 224 provides the following features:

• dbx’s Patent-Pending Advanced Feedback Suppression (AFS™)
Technology

• 24 Programmable Filters per Channel

• Stereo or Dual Mono Processing

• Live and Fixed Filter Modes

• Selectable Filter Lift Times

• Application-Specific Filter Types Include: Speech; Music Low, Music

Med, and Music High

• Input Channel Metering

• 24 Segment Filter Metering per Channel

• XLR and TRS Electronically Balanced Input and Outputs

• +4dBu / -10dBV Operating Level Switch per Channel

The AFS 224 Advantage

Key features that make the AFS 224 are its Fixed and Live Modes of operation, as well as the units
Filter Lift capabilities. The Live Mode of operation continuously updates filter placement which provides
flexibility during a performance. The Filter Lift feature automatically removes filter assignments that are
no longer necessary, which in turn, maximizes sonic integrity.

The AFS 224 allows the user to optimize the elimination of feedback. In the past, graphic equalizers were
used to eliminate feedback from a system. This was an acceptable method for eliminating feedback, but
when this method was precision tested, the result clearly showed that a single 1/3 octave EQ slider was
removing approximately half of the signal power. With AFS™, the feedback is removed automatically

2

AFS™ 224 User Manual

AFS™ 224

and the proprietary, precision AFS filters remove only a fraction of the frequency spectrum. The following
graph shows a comparison between AFS filters, the filters available in other feedback eliminators, and
conventional graphic EQ filters:

Introduction

Competitor’s
Feedback
Elimination

For more information regarding dbx Advanced Feedback Suppression (AFS™) technology, please refer to
the white paper available online at: www.dbxpro.com.

dbx AFS™

1/3 Octave EQ

Installation Recommendations

FOR RACK MOUNT USE ONLY – Install the AFS 224 in a standard-width rack with the provided
rack screws. When installed in a rack, the unit should be positioned with enough room (at least 1U above
the unit and 1U below the unit) to allow proper ventilation. The AFS 224 should not be mounted above
or below anything that generates excessive heat. Ambient temperatures should not exceed 1130F (450C)
when equipment is in use. Although the unit is shielded against radio frequency and electromagnetic
interference, extremely high fields of RF and EMI should be avoided where possible.

Connection Recommendations

The AFS 224 has balanced inputs and outputs that can be used with any balanced or unbalanced line-level
device.

To connect the AFS 224 to your sound system, refer to the following steps:

• Turn off all equipment before making connections.

• Make audio connections via XLR or 1/4” TRS connectors according to application

needs. Both types of connectors for the inputs and outputs can be used for balanced or
unbalanced connections. The use of more than one connector at a time for the inputs could
unbalance balanced lines, cause phase cancellation, short a conductor to ground, or cause
damage to other equipment connected to the AFS 224. More than one output may be used

simultaneouslyaslongasthecombinedparallelloadisgreaterthan600Ω.

• Apply power to the AFS 224. Connect the AC power cord to the AC power receptacle on the

back of the AFS 224. Route the AC power cord to a convenient power outlet away from audio
lines. The unit may be turned on and off from a master equipment power switch. Since the
AFS 224 consumes a relatively small amount of power, the unit may be left on continuously.

AFS™ 224 User Manual

3

Front & Rear Panels

AFS™ 224

Front Panel

Input Level Bar Graph

These four LEDs indicate the input signal level of the AFS 224. Input level LEDs range from -10dBu to
+18dBu.

NOTE: For maximum performance and proper operation, the average input signal level should
consistently light the 0dBu LED, with the +10dBu LED lighting occasionally.

Clip LED

This LED indicates that there is signal clipping at the input.

Bypass Button

Pressing and releasing this button will bypass the processing in the AFS 224 (LED on) and engage the AFS
processing (LED off). Pressing and holding the Bypass button will clear the filters on that channel. For
more information regarding clearing filters, see the “Clearing Filters” section of this manual.

Type Button

Pressing and holding this button allows you to link and unlink channels (see “Linking Channels”).
Pressing and releasing this button allows you to select the AFS Type. The AFS 224 offers several feedback
suppression types, which are: SPEECH, MUSIC LOW, MUSIC MED, and MUSIC HIGH. Each selected
type controls the width of the notch filter used to remove the feedback. MUSIC HIGH uses very narrow
notch filters, minimizing audible artifacts within the music. The SPEECH type uses much wider notch
filters, allowing the AFS 224 to work faster. The below table and graph further demonstrate the differences
between these filter types.

Description of AFS Types

Type Description LED Q

SPEECH Optimized for systems reproducing only speech. Not Lit 1/5th Octave

MUSIC LOW Faster response time, lower fidelity. Green 1/10th Octave

MUSIC MED Good combination of response time and fidelity. Yellow 1/20th Octave

MUSIC HIGH Slightly slower response time, high fidelity. Red 1/80th Octave

+3

+2

+1

-0

-1

-2

d

-3

B
u

-4

-5

-6

-7

-8

-9
700 1.2k750 820 850 900 .95k 1k

AFS 224 Filter Q's

Music High - 1/80th Octave

Music Med - 1/20th Octave

Music Low - 1/10th Octave

Speech - 1/5th Octave

+3

+2

+1

-0

-1

-2
d

-3

B
u

-4

-5

-6

-7

-8

-9

4

AFS™ 224 User Manual