Benchmark AHB2 Manual
Benchmark AHB2
Instruction Manual
Reference Stereo Power Amplifier
100W/channel into 8-Ohms
380W bridged mono into 8-Ohms
Contents
Fault Protection Circuitry
Introduction
3
Product Overview
3
True HRA Performance
Virtually Noise Free
Virtually Distortion Free
Patent Information
Licensed THX Patents
Important Safety Instructions
Safety Symbols
Safety Precautions
Front Panel
Front Panel Layout
Rear Panel
Rear Panel Layout
Quick Start Guide
Overview
1. Set the MODE Switch
2. Set the SENSITIVITY Switch
3. Connect the Audio Inputs
4. Connect the Speaker Outputs
5. Connect the AC Power Cord
6. Turn on the Power
7. Check the Status Indicators
Bidirectional 12 Volt Trigger
Linking Multiple Audio Components
Trigger Wiring
Trigger Cables
Automatic Power-Down Feature
40 Minute Timer
Timer Deactivates the 12V TRIGGER
No Warm-Up Required
3
3
3
3
3
4
4
5
7
7
8
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9
9
9
9
10
10
11
11
11
12
12
12
12
12
12
12
13
AUTO-ON Feature
13
Rack Mounting
14
Rack Mount Option
Rack Mounting Instructions
14
14
15
Fault-Detection Circuits
PROTECT Mode (Both MUTE Lights On)
PROTECT Mode - Fault Codes
Clipping Fault
Over-Current Fault
SOA Fault
Over-Temperature Fault
Power Supply Fault
Specifications
15
15
16
17
18
19
20
21
22
Rated Output Power
Output Current
Output Voltage
Frequency Response
Signal to Noise Ratio
Distortion
Crosstalk
Input Sensitivity
Input Impedance
Input CMRR
Trigger I/O
Damping Factor
Environmental
22
22
22
22
22
22
23
23
23
23
23
23
23
Mechanical Drawings
24
Dimensions
Rack-Mount Dimensions
24
25
Performance Plots
26
Regulatory Compliance
31
FCC and RoHS Compliance Statements
FCC Notice (U.S. Only)
RoHS Compliant Information
CE Certificate of Conformity
Safety
Warranty Information
31
31
31
32
33
34
Benchmark 1-Year Warranty
34
Benchmark Extended Warranty Options 35
Notes on Warranty Repairs
35
Consignes de Sécurité Importantes
(French)
Symboles de Sécurité
Mesures de Sécurité
Appendix
36
36
37
39
A Radical Approach to Power Amplification
39
AHB2 Instruction Manual
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Page 2
Introduction
Thank you for purchasing the Benchmark AHB2 audio power amplifier. To take full advantage of
the extraordinary performance of this amplifier, and to enjoy long and trouble-free use, please read
this manual carefully.
Product Overview
True HRA Performance
The AHB2 is a reference-grade audio power amplifier that is specifically designed to complement
the performance delivered by the finest High Resolution Audio (HRA) recording and playback
systems. The SNR and THD performance of the AHB2 put this amplifier in a class by itself.
Virtually Noise Free
The AHB2 delivers a SNR that exceeds 132 dB A-weighted. This makes the AHB2 15 to 30 dB
quieter than most top-quality power amplifiers. 132 dB is approximately equivalent to the noise
performance of a perfect 22-bit digital system.
Virtually Distortion Free
A THX-patented feed-forward error correction system virtually eliminates all traces of distortion at
all signal level and loading conditions. The AHB2 shows no traces of the crossover distortion that
can occur when push-pull outputs stages switch between output devices. Without crossover
distortion, low-level details are resolved with precision. At high output levels, the AHB2 remains
virtually distortion free while driving heavy loads.
Patent Information
The AHB2 incorporates patented THX® Achromatic™ Audio Amplifier Technology (THX
AAA™) which is licensed from THX Limited.
Licensed THX Patents







U.S. Patent No. 8,004,355
U.S. Patent No. 8,421,531
Mexico Pat. No. 312399
Mexico Pat. No. 317696
Canada Pat. No. 2753575
S. Korea Pat. No. 10-1429804
Additional Patents Pending
A complete list of applicable patents is available at: http://patents.thx.com/abc/
AHB2 Instruction Manual
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Page 3
Important Safety Instructions
Safety Symbols
This symbol alerts the user that there are important operating and maintenance
instructions in the literature accompanying this appliance.
This symbol alerts the user to the presence of uninsulated voltages within the unit that can
cause dangerous electric shocks.
This symbol alerts the user to the presence of voltages at the output connectors that can
cause dangerous electric shocks.
This symbol alerts the user that the product can only be used safely at altitudes lower than
2,000 meters.
This symbol alerts the user that the product can only be used safely in non-tropical
climates.
AHB2 Instruction Manual
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Safety Precautions
Important Operating and Maintenance Instructions
1.
2.
3.
4.
5.
6.
7.
8.
9.
Read these instructions.
Keep these instructions.
Heed all warnings.
Do not use this apparatus near water.
Do not spray any liquid onto any surface, as this may cause a dangerous condition. Clean only
with a damp cloth.
This apparatus produces heat when operated normally. Operate in a well-ventilated area. Do
not block the heat-sink fins located on either side of the unit. These emit heat and must be well
ventilated.
Do not install near any heat sources such as radiators, heat registers, stoves or other apparatus
that produce heat.
Use only with attachments and accessories specified by the manufacturer.
Use only with a stand, rack, or table designed to support the weight of this apparatus. Make
sure that injury or damage will not result from cables pulling on the apparatus or its mounting.
Speaker Output Voltage Warning
10. The speaker outputs are capable of producing dangerous voltages. Use insulated speaker
connections. Unplug the apparatus before making changes to the speaker output connections.
Hazardous Internal Voltage Warnings
11. Refer all servicing to qualified service personnel. There are no user-serviceable parts inside the
unit. There are exposed high voltages inside the unit and these may persist after the unit is
unplugged. Do not attempt to open any of the covers, and do not remove any fasteners.
Opening the unit will void the warranty.
12. Certain parts are safety related, or are required to meet certain regulations. All parts must be
replaced with exact replacements unless written approval is granted by Benchmark.
Unauthorized substitutions and modifications can create unsafe or non-compliant operating
conditions and will void the warranty. Unauthorized modifications may cause fire and shock
hazards. Unauthorized modification may cause the unit to emit excessive radio and magnetic
interference. Modifications may reduce the immunity to external interference. Do not refer
servicing to personnel who offer product modification services.
AHB2 Instruction Manual
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Line Cord and Fuse Warnings
13. The AC line cord is removable. Use a grounded 3-prong line cord that is appropriate for your
region. Your dealer can provide you with the correct line cord.
14. Do not defeat the purpose of the grounded power plug. The ground prong is provided for your
safety. When a 3-prong outlet is not available, please consult an electrician for replacement of
the obsolete outlet. Do not use 2-prong to 3-prong adapters. Do not attempt to solve AC hum
problems by lifting the AC safety ground!
15. Unplug this apparatus during lightning storms or when unused for long periods of time.
16. This apparatus is equipped with an auto-ranging power supply. There is no internal voltage
selection switch - do not attempt to open the unit. Operating voltage ranges are 100 to 120 Vac
+/- 10%, and 220 to 240 Vac +/- 10%. Operating frequency is 50 to 60 Hz. All operating
voltages use the same fuse size.
17. For continued fire and shock protection always replace the fuses with the correct size and type
(T 8A H 250V, 5x20mm), (T = time lag, 8A = eight Amps, H = high breaking capacity, 250V =
voltage rating, 5x20mm = cartridge size). High-breaking fuses use a ceramic body. Use Bel
Fuse 5HT 8-R, or Schurter 0001.2513, or an exact equivalent. The fuse drawer includes two
fuses. Always replace both fuses at the same time.
Operating Environment Warnings
18.
This product can only be used safely at altitudes lower than 2,000 meters.
19.
This product can only be used safely in non-tropical climates.
AHB2 Instruction Manual
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Front Panel
Front Panel Layout
Left to Right:
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
Power Switch
Power Indicator
Channel 1 Clip Indicator
Channel 1 Temperature and High-Current Indicator
Channel 1 Mute Indicator
Channel 2 Mute Indicator
Channel 2 Temperature and High-Current Indicator
Channel 2 Clip Indicator
AHB2 Instruction Manual
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Rear Panel
Rear Panel Layout
Top Row, Left to Right:



Channel 2 Speaker Binding Posts
AC Power Entry with Fuse Drawer
Channel 1 Speaker Binding Posts
Bottom Row, Left to Right:
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

12 Volt Trigger Input / Output Connector
3-Position Sensitivity Switch - Sets Gain
Balanced XLR Input for Channel 2
NL4 Speaker Output for Channel 2
NL4 Speaker Output for Bridged Mono Operation
NL4 Speaker Output for Channel 1, or Channels 1 and 2
Balanced XLR Input for Channel 1, or for Bridged Mono
2-Position Mode Switch - Enables Bridged Mono Mode
12 Volt Trigger Input / Output Connector
AHB2 Instruction Manual
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Quick Start Guide
Overview



Connect all cables before turning the unit on.
Check the settings of the MODE and SENSITIVITY switches before turning the unit on.
Turn down the audio source before turning the unit on for the first time.
1. Set the MODE Switch
The MODE switch is very important, make sure it is set correctly for your application. An incorrect
setting will not cause damage, but it may cause low output levels, a missing channel, or a polarity
inversion.
The AHB2 power amplifier can be run in two modes:


STEREO mode - Two output channels
MONO mode - One output channel in bridged mono
The bridged MONO mode will deliver almost 4 times as much power into an 8-Ohm speaker, and
will do so without any increase in distortion. The MONO mode is an excellent choice for high-power
applications. In MONO mode, two amplifiers will be required for stereo operation.




Set
Set
Set
Set
this
this
this
this
switch
switch
switch
switch
to
to
to
to
STEREO if the AHB2 is driving a stereo pair of speakers.
STEREO if the AHB2 is driving two channels of a multi-channel system.
STEREO if the AHB2 is driving a biamped two-way speaker.
MONO if the AHB2 is driving one speaker.
2. Set the SENSITIVITY Switch
The SENSITIVITY switch must be set properly in order to maximize the signal to noise ratio of
your audio system. If this switch is set too low, you will not be able to drive the amplifier to its
rated output. If this switch is set too high, the noise produced by your preamplifier will be amplified
more than is necessary.





If you are using an unbalanced input, you must use one of the top two switch positions.
If you are using a balanced input, you will usually need to use one of the bottom two switch
positions.
Set this switch all the way down if you are using professional balanced sources.
Raise the switch to increase the output level.
Lower the switch to decrease the output level.
When set properly, you should be able to drive the amplifier to the onset of clipping when your
volume control is set near maximum.
AHB2 Instruction Manual
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3. Connect the Audio Inputs
There are two balanced XLR audio inputs on the AHB2:


1 IN/MONO IN
2 IN
Special adapter cables are required if balanced sources are not available. The adapter cables
extend a three-wire balanced connection back to an unbalanced RCA output. The adapter cables
are available from Benchmark.



Use 1 IN/MONO IN for the left channel of a stereo system.
Use 2 IN for the right channel of a stereo system.
Use 1 IN/MONO IN for all MONO mode applications.
Please note that unbalanced sources will limit the overall performance of the playback system. This
is not due to any limitations in the AHB2. It is due to the noise limitations of unbalanced output
drive stages. High-level balanced interconnects are required in low-noise systems. We highly
recommend balanced interconnects.
4. Connect the Speaker Outputs
The AHB2 has twist-lock NL4 SpeakON connectors that provide very high-quality speaker
connections. These connectors outperform most binding posts, have very low resistance, and are
designed to reliably carry high current. These jacks are compatible with two-pole NL2 plugs or four
pole NL4 plugs. For best performance, make all speaker connections using twist-lock SpeakON
connectors. Binding posts are included to provide compatibility with existing speaker cables.



Use 1+ and 1- for the channel 1 output in STEREO mode.
Use 2+ and 2- for the channel 2 output in STEREO mode.
Use M+ and M- for the output in MONO mode.
The 1&2 OUT NL4 jack provides access to channels 1 and 2. If an NL2 plug is inserted into this
jack, it will have access to channel 1 only. Use this jack with a two-pole cable to connect the
channel 1 output to the left speaker in a stereo system.
The 2 OUT NL4 jack provides access to channel 2 only. Use this jack with a two-pole cable to
connect the channel 2 output to the right speaker in a stereo system.
The BRIDGED MONO OUT NL4 jack provides a dedicated output for bridged mono applications.
Use this jack with a two-pole cable to connect the bridged output to a single speaker.
The 1&2 OUT NL4 jack can also be used for biamp applications. Use this jack with a four-pole
cable to connect both output channels to the high and low drivers in a biamped 2-way
speaker.
AHB2 Instruction Manual
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5. Connect the AC Power Cord
The AC input connector accepts standard IEC input cables. Use a grounded cable that is
appropriate for your location. The AC input is auto ranging and may be used internationally without
changing any settings or fuse sizes. Fuses are located in a drawer at the top of the AC input
connector.
6. Turn on the Power


Turn down the audio source before turning the unit on for the first time.
Press the POWER button to turn the unit on or off.
Note: Audio will automatically mute on startup and shutdown to protect the speakers and
eliminate unwanted transients.
7. Check the Status Indicators
The amplifier has the following status indicators:




POWER - Power-status indicator, On = Normal, Flashing = Fault
CLIP (one per channel) - Audio-clip indicator, Flash = Clip, Off = Normal, On = Fault
TEMP (one per channel) - Over-temperature/current indicator, Off = Normal, On = Fault
MUTE (one per channel) - Channel-mute indicator, Off = Normal, On = PROTECT or MUTE
POWER - Power Status Indicator



Off = Power is Off
On = Normal Operation
Flash = Fault Condition, Power Supply has Shut Down, PROTECT
CLIP - Audio Clipping Indicators



Off = Normal
Left or Right Flashing = Some Clipping is Occurring
On = Fault Condition, Excessive Clipping has Occurred, PROTECT
TEMP - Over-Temperature Indicators





Off = Normal
Left or Right Flashing = Peak-Current Warning
Left or Right On and POWER On = Over-Current Fault, PROTECT
Left or Right On and POWER Flashing = Over-Temperature Fault, PROTECT
Both On = Other Fault Conditions, PROTECT
MUTE - Audio Mute Indicators



Off = Normal
Both On During Start Up or Shut Down = Normal, Audio is Muted
Both On = PROTECT or MUTE Mode, Audio is Muted
AHB2 Instruction Manual
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Bidirectional 12 Volt Trigger
Benchmark has reinvented the 12 volt trigger by adding bidirectional signaling. The trigger
connection on the AHB2 can be used as an input, an output, or both. It is compatible with any
common 12 volt trigger input or output. The 12V TRIGGER can be used to turn the AHB2 power
amplifier on or off automatically in sequence with other audio system components. The AHB2 can
also turn other connected components on and off.
Linking Multiple Audio Components
Two or more AHB2 power amplifiers can be linked together with 12V TRIGGER CABLES, so that
all units power up and down together. This group of amplifiers can be linked to a group of
Benchmark DAC2 D/A converters. In such a system, any power button can be used to turn the
system on or off.
Trigger Wiring
The AHB2 has two bi-directional 12V TRIGGER I/O jacks. These jacks are 1/8" (3.5 mm) TRS
connectors. The tip is wired to the 12V TRIGGER I/O bus. The sleeve is wired to chassis ground.
There is no connection to the ring.
Trigger Cables
The AHB2 includes one 3-foot (1 m) 12V TRIGGER CABLE. This cable has a 1/8" (3.5 mm) TRS
connector at each end.
Automatic Power-Down Feature
40 Minute Timer
The AHB2 has an audio signal presence detector on each input channel. If no audio is detected on
either input for a period of 40 minutes, the AHB2 will automatically shut down to save energy. This
feature is required by law in many countries, and can contribute to significant energy savings.
This auto-off feature is programmable. Starting with the unit on, press and hold the POWER button
for 7 seconds to toggle this feature (press and hold the POWER button until the MUTE lights turn
off). This setting is stored in memory and is recalled when the unit is turned on.
Press and hold the power button for 1 second to view the status of this feature. If the timer is
enabled, the TEMP lights will turn on while the POWER button is pressed.
Timer Deactivates the 12V TRIGGER
When the AHB2 executes an automatic power down, it will pull the 12V TRIGGER low to shut
down any equipment attached to the trigger bus. The timer is only active when the system is
started using the POWER button on the front of the AHB2.
AHB2 Instruction Manual
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No Warm-Up Required
Unlike most power amplifiers, the AHB2 reaches its full rated performance very quickly. Full rated
performance is reached in less than one minute. For this reason, there is absolutely no reason to
keep the AHB2 powered on when not in use. The feed-forward error correction circuits in the
AHB2 keep it very stable over a wide range of operating temperatures.
AUTO-ON Feature
The AHB2 has a programmable AUTO-ON feature. When this feature is enabled, the AHB2 will
automatically turn on whenever AC power is applied. The 40-minute timer is automatically disabled
when this feature is activated. The POWER button will act as a MUTE button when this feature is
enabled. When AUTO-ON is enabled, the POWER button will toggle MUTE on and off. In MUTE
MODE, the POWER light and MUTE lights are on, and all other lights are off.
To enable the AUTO-ON feature, start with the unit off. Then press and hold the POWER button for
3 seconds. The CLIP lights will turn on at the end of 3 seconds. Release the POWER button as soon
as the CLIP lights turn on. Press the POWER button to verify that the AUTO-ON mode is enabled. If
it is enabled, the POWER button will toggle MUTE on and off.
To disable the AUTO-ON feature, start with the unit on. Then press and hold the POWER button for
3 seconds. The clip lights will turn off at the end of 3 seconds. Release the Power button as soon as
the CLIP lights turn off. The unit should now turn off (verifying that the feature has been disabled).
AHB2 Instruction Manual
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Rack Mounting
The AHB2 is available in a rack-mount version. The AHB2 is magnetically shielded, and will not
interfere with sensitive equipment mounted above or below the AHB2.
Rack Mount Option
Rack Mounting Instructions
The AHB2 runs very cool when idle and runs very cool under most load conditions. However, it can
produce significant heat when heavily loaded. Make sure the rack is adequately ventilated. Make
sure the side heat sinks have an unobstructed air flow.
Some power amplifiers can emit very strong magnetic fields. These amplifiers should be kept at
least two rack units above or below the AHB2. Magnetic interference can produce hum problems.
If the AHB2 is mounted directly above another piece of equipment, it may be necessary to remove
the feet from the AHB2. Save the feet for future needs. Replacement feet may be purchased
directly from Benchmark or through most authorized Benchmark dealers.
AHB2 Instruction Manual
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Fault Protection Circuitry
The AHB2 is designed to detect overloads, short circuits, clipping, excessive temperatures, high
DC offsets, and low AC input voltages. When a potentially-damaging fault occurs, the amplifier
enters a special "PROTECT" mode to prevent damage.
The amplifier has a comprehensive set of fault-detection circuits that will activate the PROTECT
mode to protect against damage to the amplifier or speakers.
Fault-Detection Circuits









Temperature sensor on each output channel
Temperature sensor on main power supply
Current sensor on each output channel
Voltage clip detector on each output channel
DC offset detector on each output channel
SOA (safe operating area) detector on each output channel
Load sensor on main power supply
Fault sensors on all power supplies
AC line under-voltage fault sensor on AC input
PROTECT Mode (Both MUTE Lights On)
In PROTECT mode, both MUTE lights are on. The CLIP, TEMP, and POWER lights identify
the cause of the fault.
The PROTECT mode is only activated when a potentially damaging fault condition has occurred. To
protect against damage, both audio outputs are muted. In some fault conditions, all high-power
circuits are shut off. A small auxiliary power supply remains active so that the error condition can
be displayed on the front panel.
If the POWER light is flashing, all high-power circuits have been shut down as an additional
precaution.
If a fault has triggered the PROTECT mode, the amplifier must be turned off before
normal operation can resume. Identify and correct the cause of the fault before
restarting the amplifier.
AHB2 Instruction Manual
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Page 15
PROTECT Mode - Fault Codes
The following table provides a summary of all possible status display conditions. The MUTE lights
will turn on and stay on whenever a fault condition has triggered the PROTECT mode.
If a fault has occurred, power must be turned off before normal operation can resume.
Identify and correct the cause of the fault before restarting the amplifier.
POWER
OFF
ON
ON
ON
ON
ON
ON
ON
FLASH
FLASH
FLASH
ON
ON
ON
FLASH
FLASH
FLASH
ON
CLIP
OFF
ON
OFF
OFF
FLASH
OFF
OFF
OFF
ON
OFF
ON
OFF
OFF
OFF
OFF
OFF
ON
ON
TEMP
OFF
ON
OFF
OFF
OFF
OFF
FLASH
OFF
OFF
OFF
OFF
ON
OFF
ON
ON
OFF
ON
ON
MUTE
OFF
ON
ON
OFF
OFF
OFF
OFF
OFF
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
AHB2 Instruction Manual
MUTE
OFF
ON
ON
OFF
OFF
OFF
OFF
OFF
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
TEMP
OFF
ON
OFF
OFF
OFF
OFF
OFF
FLASH
OFF
OFF
OFF
OFF
ON
ON
OFF
ON
ON
ON
Rev G
CLIP
OFF
ON
OFF
OFF
OFF
FLASH
OFF
OFF
OFF
ON
ON
OFF
OFF
OFF
OFF
OFF
ON
ON
Status
Power off, or no AC input
AC Startup - lamp test
Mute on - startup or shutdown
Normal operation, no errors
Channel 1 - Clipping
Channel 2 - Clipping
Channel 1 - Current warning
Channel 2 - Current warning
Channel 1 - Clipping Fault
Channel 2 - Clipping Fault
Chan 1&2 - Clipping Fault
Channel 1 - Over-Current Fault
Channel 2 - Over-Current Fault
Chan 1&2 - Over-Current Fault
Channel 1 - Over Temperature
Channel 2 - Over Temperature
Power Supply Fault, Loss of AC
SOA Fault
Page 16
Clipping Fault
The input and output audio signals are compared to determine when clipping is occurring.
Occasional clipping will cause the CLIP lights to flash and will not trigger this fault. However, if a
severe overdrive condition occurs, this fault is triggered to prevent damage to speakers. This fault
indicates that the amplifier has been driven very hard into voltage clipping. Both channels are
muted to protect the amplifier and speakers. A power reset will be required.
Fault Display:




POWER light is Flashing
Both MUTE lights are On
One or both CLIP lights are On
Both TEMP lights are Off
Typical Causes:


The sensitivity switch may be set too high
Output of preamplifier or DAC is too high
Required Actions:




Check the position of the SENSITIVITY switch
Move the sensitivity switch down one or two positions if necessary
Turn down the audio source
Restart the amplifier
AHB2 Instruction Manual
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Page 17
Over-Current Fault
The output current of each channel is constantly monitored. If either channel exceeds a safe output
current, this fault is triggered and both channels are muted to protect the amplifier and speakers. A
power reset will be required.
Fault Display:




POWER light is On
Both MUTE lights are On
Both CLIP lights are Off
One or both TEMP lights are On
Typical Causes:


The load impedance of the speakers may be too low
Speaker cables may be shorted
Required Actions:





Check for shorted speaker cables
Make sure the nominal Stereo load impedance is 3 Ohms or higher
Make sure the nominal Bridged Mono load impedance is 6 Ohms or higher
Turn down the audio source
Restart the amplifier
Speaker impedance always varies with frequency. Speaker impedance may be much lower than the
rated "nominal" impedance at certain frequencies. The over-current fault detection circuits prevent
potential damage that can be caused by driving very high signal levels into very low impedances.
In STEREO mode, at full output, the current limit can be reached if the load impedance dips below
about 1.3 Ohms. In MONO mode, at full output, the current limit can be reached if the load
impedance dips below about 2.6 Ohms.
AHB2 Instruction Manual
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Page 18
SOA Fault
The SOA (Safe Operating Area) of the output power devices is constantly monitored. If this safe
operating area is violated, both channels are muted to protect the amplifier and speakers. A power
reset will be required.
Fault Display:




POWER light is On
Both MUTE lights are On
Both CLIP lights are On
Both TEMP lights are On
Typical Causes:



The load impedance of the speakers may be too low
Speaker cables may be shorted
Amplifier has been overloaded with a high-amplitude test tone
Required Actions:





Check for shorted speaker cables
Make sure the nominal STEREO load impedance is 3 Ohms or higher
Make sure the nominal Bridged MONO load impedance is 6 Ohms or higher
Turn down the audio source
Restart the amplifier
AHB2 Instruction Manual
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Page 19
Over-Temperature Fault
The temperature of the left and right heat sinks are constantly monitored. If either heat sink
reaches the maximum allowable temperature, both channels are muted to protect the amplifier and
speakers. All high-power subsystems are shut down to accelerate the cooling process. One or both
heat sinks will be very hot. After the unit cools, a power reset will be required.
Fault Display:




POWER light is Flashing
Both MUTE lights are On
Both CLIP lights are Off
One TEMP light is On
Typical Causes:



The load impedance of the speakers may be too low
Heat sinks may be obstructed
Amplifier has been overloaded with a high-amplitude test tone
Required Actions:






Make sure the nominal STEREO load impedance is 3 Ohms or higher
Make sure the nominal Bridged MONO load impedance is 6 Ohms or higher
Maintain adequate clearance around heat sinks
Allow time for the amplifier to cool
Turn down the audio source
Restart the amplifier
AHB2 Instruction Manual
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Page 20
Power Supply Fault
The power supply has a number of sensors that monitor voltage, current, and temperature. If any
parameter exceeds safe limits, both channels are muted to protect the amplifier and speakers. This
fault may indicate that the AC power has been interrupted. It may also indicate that the power
supply has overheated. It may also indicate the detection of an overload on one of the power
supply rails. It may also indicate a fault condition in the power supply system. All high-power
subsystems are shut down. A power reset will be required.
Fault Display:




POWER light is Flashing
Both MUTE lights are On
Both CLIP lights are On
Both TEMP lights are On
This fault display will only persist if AC is present.
In the event of a total loss of AC power, this error display will stay on for about 15-30
seconds and then all lights will turn off.
Typical Causes:





The AC line voltage may have dropped below allowable limits for a few seconds
AC power has been lost (if all lights turn off after about 15-30 seconds)
The load impedance of the speakers may be too low
Heat sinks may be obstructed
Amplifier has been overloaded with a high-amplitude test tone
Required Actions:







Check the AC power source
Make sure the nominal STEREO load impedance is 3 Ohms or higher
Make sure the nominal Bridged MONO load impedance is 6 Ohms or higher
Maintain adequate clearance around heat sinks
If unit is hot, allow time to cool
Turn down the audio source
Restart the amplifier
AHB2 Instruction Manual
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Page 21
Specifications
Rated Output Power
1 kHz, < 0.00015% THD







100
130
190
240
200
380
480
W/channel into 8 Ohms, both channels
W/channel into 6 Ohms, both channels
W/channel into 4 Ohms, both channels
W/channel into 3 Ohms, both channels
W Bridged Mono into 16 Ohms
W Bridged Mono into 8 Ohms
W Bridged Mono into 6 Ohms
driven
driven
driven
driven
Output Current

29 A peak into 1 Ohm, both channels driven
Output Voltage

> 80 Vpp into any rated load
Frequency Response



Better than 0.1 Hz to 200 kHz, +0/-3 dB
-0.01 dB at 20 Hz, -0.17 dB at 20 kHz, 8-Ohm Load
-0.23 dB at 20 Hz, -0.32 dB at 20 kHz, 4-Ohm Load
Signal to Noise Ratio




132
135
130
133
dB
dB
dB
dB
A-Weighted, Stereo Mode
A-Weighted, Bridged Mono
Unweighted, 20 Hz to 20 kHz, Stereo Mode
Unweighted, 20 Hz to 20 kHz, Stereo Mode
Distortion
THD+N



1 kHz, 80 kHz LPF, at full rated output into any rated load
< -118 dB (< 0.00013%) - Stereo Mode
< -118 dB (< 0.00013%) - Mono Mode
THD
1 kHz, 20 kHz LPF, at full rated output into any rated load


< -119 dB (< 0.00011%) - Stereo Mode
< -120 dB (< 0.00010%) - Mono Mode
AHB2 Instruction Manual
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Crosstalk


Better than -115 dB at 1 kHz
Better than -92 dB at 20 kHz
Input Sensitivity





Low-Gain = 22 dBu (9.8 Vrms)
Mid-Gain = 14.2 dBu (4 Vrms)
High-Gain = 8.2 dBu (2 Vrms)
Use Mid-Gain or High-Gain settings for unbalanced inputs
Unbalanced inputs require RCA to XLRM adapter cables
Input Impedance


50 k Ohms, normal mode
1 M Ohm, common mode
Input CMRR



80 dB at 20 Hz, typical
80 dB at 1 kHz, typical
65 dB at 20 kHz, typical
Trigger I/O








12 VDC 200 mA current-limited output to trigger turn-on of remote devices
DC input for slaving to remote devices
Input responds to 3.3 V logic and higher, VIL = 1.26 V, VIH = 2.7 V
Absolute maximum input voltage = 30 Vdc
Absolute minimum input voltage = -0.3 Vdc
Input Impedance = 20 k Ohms
Two 1/8" (3.5 mm) TRS jacks
Tip = 12 Volt Trigger I/O, Ring = no connection, Sleeve = chassis ground
Damping Factor




350 at 20 Hz,
254 at 1 kHz,
34 at 20 kHz,
7 at 200 kHz,
8-Ohms
8-Ohms
8-Ohms
8-Ohms
Environmental


0° C to 50° C (32° F to 122° F) Ambient Temperature
Up to 80% Humidity - Non-condensing
AHB2 Instruction Manual
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Page 23
Mechanical Drawings
Dimensions
AHB2 Instruction Manual
Rev G
Page 24
Rack-Mount Dimensions
AHB2 Instruction Manual
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Page 25
Performance Plots
Figure 1 – THD vs. Output Power - 4-Ohm Load
This plot shows the extraordinary THD performance of the AHB2. The feed-forward error correction
circuits keep the output nearly distortion free.
The magenta curve is the output power. Power is shown on the right-hand vertical scale.
The green trace is the THD measured at the output of the left channel when loaded with 4-Ohms.
The red trace is the THD measured at the output of the right channel when loaded with 4-Ohms.
THD is shown on the left-hand scale.
The stair steps are caused by the THD within the AP2722. This stair stepping demonstrates that the
AHB2 is at or below the measurement limits of the AP2722 test set, even when the AHB2 is
driving a heavy load.
AHB2 Instruction Manual
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Page 26
Figure 2 – THD vs. Output Power - 8-Ohm Load
This plot shows the THD of the AHB2 with an 8-Ohm load. Note that the results are almost
identical to those shown in Figure 1 (with a 4-Ohm load). Together, these two plots demonstrate
that the THD performance of the AHB2 does not change with load.
AHB2 Instruction Manual
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Page 27
Figure 3 – THD vs. Output Power, Bridged Mono - 8-Ohm Load compared to No-Load
This plot also shows that the THD produced by the AHB2 does not increase with loading. The red
trace is the no-load THD performance in bridged mono mode. The green trace is the THD
performance while driving an 8-Ohm load in bridged mono mode. Note that the AHB2 shows no
signs of increased distortion while delivering 397 W into 8-Ohms bridged mono.
AHB2 Instruction Manual
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Page 28
Audio Precision
01/13/15 09:10:15
dx=.979800 kHz
400
dy=96.30 X/Y
350
350.4
300
250
254.1
X
/
Y
200
150
100
50
0
10
20.2
20
50
100
200
1k
500
2k
5k
10k
20k
50k
100k
200k
Hz
Sweep
Trace
Color
Line Style
Thick
Data
Axis
1
1
Red
Solid
4
Anlr.Ratio
Left
Comment
Cursor1
*350.4
Cursor2
X/Y
*254.1
X/Y
Damping_Factor_8Ohm.at27
Figure 4 – Damping Factor - 8-Ohm Load
This plot shows that the AHB2 provides excellent damping to keep speakers tightly controlled.
AHB2 Instruction Manual
Rev G
Page 29
Figure 5 – FFT at 320W, 1 kHz, 8-Ohms Bridged Mono
This FFT plot shows the spectral purity of the AHB2. The green trace is the no-load performance.
The red trace is the performance at 320 W. Both are nearly identical. The 1 kHz fundamental has
been removed with a notch filter to improve the resolution of the AP2722 test set. The 2nd
harmonic measures -131.5 dB relative to the 1 kHz fundamental. The 3rd harmonic measures
-122.5 dB relative to the 1 kHz fundamental. The only other harmonic visible is the 5th and this
measures about -139 dB relative to the fundamental.
AHB2 Instruction Manual
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Page 30
Regulatory Compliance
FCC and RoHS Compliance Statements
FCC Notice (U.S. Only)
NOTICE: This equipment has been tested and found to comply with the limits for a Class B
digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide
reasonable protection against harmful interference in a residential installation. This equipment
generates, uses, and can radiate radio frequency energy and, if not installed and used in
accordance with the instructions, may cause harmful interference to radio communications.
However, there is no guarantee that interference will not occur in a particular installation. If
this equipment does cause harmful interference to radio or television reception, which can be
determined by turning the equipment off and on, the user is encouraged to try to correct the
interference by one or more of the following measures:




Reorient or relocate receiving antenna.
Increase the separation between the equipment and receiver.
Connect the equipment into an outlet on a circuit different from that to which the receiver is
connected.
Consult the dealer or an experienced radio/TV technician for help.
This device complies with Part 15 of the FCC rules. Operation is subject to the following two
conditions:
1. This device may not cause harmful interference.
2. This device must accept any interference received including interference that may cause
undesired operation.
Instructions to Users: This equipment complies with the requirements of FCC (Federal
Communication Commission) equipment provided that following conditions are met:

RCA Digital Connections: Shielded 75-Ohm coaxial cable must be used.
NOTICE: Changes or modifications not expressly approved by the party responsible for
compliance could void the user's authority to operate the equipment.
RoHS Compliant Information
This statement clarifies Benchmark Media Systems, Inc. product compliance with the EU’s
(European Union) directive 2002/95/EC, or, RoHS (Restrictions of Hazardous Substances).
As of July 01, 2006, All Benchmark Media Systems, Inc. products placed on the European Union
market are compliant (containing quantity limit weight less than or equal to 0.1% (1000 ppm)
of any homogeneous Lead (Pb), Mercury (Hg), Hexavalent Chromium (Cr VI), and flame
retardant Polybrominated Biphenyls (PBB) or Polybrominated Diphenyl Ethers (PBDE)).
AHB2 Instruction Manual
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Page 31
CE Certificate of Conformity
AHB2 Instruction Manual
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Page 32
Safety
Product: Audio Amplifier, Audio Equipment, Stereo Audio Amplifier
Model: AHB2
Part Number: 500-18000-xx0
Parameters:




Rated Input Voltage: 100-120 Vac; 220-240 Vac
Rated Frequency: 50/60 Hz
Rated Input Current: 8A
Protection Class: I
Tested according to:



CAN/CSA C22.2 60065/A1:2006
UL 60065:2007
EN60065/A12:2011
Certification Mark:
AHB2 Instruction Manual
Rev G
Page 33
Warranty Information
Benchmark 1-Year Warranty
The Benchmark 1-Year Warranty
Benchmark Media Systems, Inc. warrants its products to be free from defects in material and
workmanship under normal use and service for a period of one year from the date of
delivery.
This warranty extends only to the original purchaser. This warranty does not apply to fuses,
lamps, batteries, or any products or parts that have been subjected to misuse, neglect,
accident, modification, or abnormal operating conditions.
In the event of failure of a product under this warranty, Benchmark Media Systems, Inc. will
repair, at no charge, the product returned to its factory. Benchmark Media Systems, Inc. may,
at its option, replace the product in lieu of repair. If the failure has been caused by misuse,
neglect, accident, or, abnormal operating conditions, repairs will be billed at the normal shop
rate. In such cases, an estimate will be submitted before work is started, if requested by the
customer.
Attempts to deliberately deface, mutilate, or remove the product's label will render this
warranty void. Benchmark will not honor warranties for any products disingenuously purchased
on the US or Canadian markets for export.
The foregoing warranty is in lieu of all other warranties, expressed or implied, including but not
limited to any implied warranty of merchantability, fitness or adequacy for any particular
purpose or use. Benchmark Media Systems, Inc. shall not be liable for any special, incidental,
or consequential damages, and reserves the right to change this information without notice.
This limited warranty gives the consumer-owner specific legal rights, and there may also be
other rights that vary from state to state.
AHB2 Instruction Manual
Rev G
Page 34
Benchmark Extended Warranty Options
The Benchmark Extended 5-Year Warranty *
Benchmark Media Systems, Inc. optionally extends the standard 1-year warranty to a period of
five years from the date of delivery.
*For the extended warranty to become effective, the original purchaser must register the
product at the time of purchase either by way of the enclosed registration card or through the
product registration section of the Benchmark Media Systems, Inc. website. This optional
warranty applies only to products purchased within the US and Canada and is extended only to
the original purchaser.
Attempts to deliberately deface, mutilate, or remove the product's label will render this
warranty void. Benchmark will not honor warranties for any products disingenuously purchased
on the US or Canadian markets for export. The terms of the extended warranty are subject to
change without notice. For products purchased outside the US and Canada, please refer to the
Extended Two 2-Year International Warranty.
The Benchmark Extended 2-Year International Warranty **
Benchmark Media Systems, Inc. optionally extends the standard 1-year warranty to a period of
two years from the date of delivery.
**For the extended warranty to become effective, the original purchaser must register the
product at the time of purchase either by way of the enclosed registration card or through the
product registration section of the Benchmark Media Systems, Inc. website. This optional
warranty applies only to products purchased outside the US and Canada and is extended only
to the original purchaser.
Attempts to deliberately deface, mutilate, or remove the product's label will render this
warranty void. Benchmark will not honor warranties for any products disingenuously purchased
on the US or Canadian markets for export. The terms of the extended warranty are subject to
change without notice. For products purchased in within the US and Canada, please refer to the
Extended Five 5-Year Warranty.
Notes on Warranty Repairs
An RMA (return merchandise authorization) number, issued by our Customer Service
Department, is required when sending products for repair.
They must be shipped to Benchmark Media Systems prepaid and preferably in their original
shipping carton with the RMA number clearly visible on the exterior of the packaging. A letter
should be included giving full details of the difficulty.
AHB2 Instruction Manual
Rev G
Page 35
Consignes de Sécurité Importantes (French)
Symboles de Sécurité
Ce symbole avertit l'utilisateur d'importantes instructions de fonctionnement et d'entretien
dans la documentation accompagnant cet appareil.
Ce symbole avertit l'utilisateur de la présence de tensions isolées à l'intérieur de l'unité qui
peuvent provoquer des chocs électriques dangereux.
Ce symbole avertit l'utilisateur de la présence de tensions sur les connecteurs de sortie qui
peuvent causer des chocs électriques dangereux.
Ce symbole avertit l' utilisateur que le produit ne peut être utilisé en toute sécurité à des
altitudes inférieures à 2000 mètres.
Ce symbole avertit l' utilisateur que le produit ne peut être utilisé en toute sécurité dans
les climats non tropicaux.
AHB2 Instruction Manual
Rev G
Page 36
Mesures de Sécurité
1.
2.
3.
4.
5.
6.
7.
8.
9.
Lisez ces instructions.
Conservez ces instructions.
Respectez tous les avertissements.
N'utilisez-pas cet appareil près de l'eau.
Ne pulvérisez-pas un liquide sur une surface quelconque, car cela pourrait provoquer une
situation dangereuse. Nettoyez-le uniquement avec un chiffon humide.
Ce dispositif génère de la chaleur lorsqu'il fonctionne normalement. Opérez dans un endroit
bien ventilé. Ne bloquez-pas les ailettes du dissipateur de chaleur situées de chaque côté de
l'appareil. Celles-ci émettent de la chaleur et doivent être bien ventilées.
N'installez-pas l'appareil à proximité de sources de chaleur telles que des radiateurs, registres
de chaleur, poêles ou autres appareils produisant de la chaleur.
Utilisez uniquement avec des pièces jointes et des accessoires spécifiés par le fabricant.
Utilisez seulement avec un stand, support ou une table conçue pour supporter le poids de
l'appareil. Assurez-vous que des blessures ou des dommages ne se traduiront pas par des
câbles tirés sur l'appareil ou son montage.
10. Les sorties haut-parleurs sont capables de produire des tensions dangereuses. Utilisez des
connexions de haut-parleurs isolées. Débranchez l'appareil avant de modifier les connexions de
sortie de haut-parleur.
11. Confiez toute réparation à un personnel qualifié. Il n'y a pas de pièce réparable par l'utilisateur
à l'intérieur de l'appareil. Il y a des tensions élevées exposées à l'intérieur de l'unité et celles-ci
peuvent persister après que l'appareil est débranché. Ne tentez pas d'ouvrir l'un des couvercles,
et ne retirez-pas les attaches. L'ouverture de l'unité annulera la garantie.
12. Certaines pièces sont liées à la sécurité, ou sont tenues de respecter certaines règles. Toutes
les pièces doivent être remplacées par des remplacements exacts sauf autorisation écrite
accordée par référence. Les substitutions et modifications non autorisées peuvent créer des
conditions de fonctionnement dangereuses ou non conformes qui annuleront la garantie. Les
modifications non autorisées peuvent entraîner des risques d'incendie et d'électrocution. Toute
modification non autorisée peut entraîner l'appareil à émettre des ondes excessive et les
interférences magnétiques. Des modifications peuvent réduire l'immunité aux perturbations
extérieures. Ne faites appel un personnel qui offrent des services de modification de produit.
AHB2 Instruction Manual
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Page 37
13. Le cordon du CA est amovible. Utilisez un cordon 3 broches mis à la terre approprié à votre
région. Votre revendeur peut vous fournir le cordon correct.
14. Ne pas oublier le but de la prise de courant mise à la terre. La prise de terre est fournie pour
votre sécurité. Quand une prise 3 broches n'est pas disponible, veuillez consulter un électricien
pour remplacer la prise obsolète. Ne pas utiliser d'adaptateurs 2 broches vers 3 broches. Ne pas
tenter de résoudre les problèmes de bruissement en soulevant sécurité terre du CA !
15. Débranchez cet appareil pendant les orages ou si vous le laissez inutilisé pendant de longues
périodes de temps.
16. Cet appareil est équipé d'une alimentation intégrée auto-adaptable. Il n'y a pas de
commutateur de sélection de tension interne - ne tentez pas d'ouvrir l'appareil. Les gammes de
tension de fonctionnement vont de 100 à 120 Vac +/- 10%, et de 220 à 240 Vac +/- 10%. La
fréquence de fonctionnement est de 50 à 60 Hz. Toutes les tensions d'exploitation utilisent le
même type de fusible.
17. Pour une protection anti-feu et anti-chocs continue remplacez toujours les fusibles avec la
bonne taille et le bon type (T 8A H 250V, 5x20mm), (T = temps de retard, 8A = huit ampères,
H = haut pouvoir de coupure, 250V = tension nominale, 5x20mm = taille de la cartouche). .
Les fusibles ultrarupture utilisent un corps en céramique. Utilisez Bel Fuse 5HT 8-R, ou Schurter
0001.2513, ou un modèle exactement équivalent. Le porte-fusible comprend deux fusibles.
Toujours remplacer les deux fusibles en même temps.
18. Ce produit ne peut être utilisé en toute sécurité à des altitudes inférieures à 2000 mètres.
19. Ce produit ne peut être utilisé en toute sécurité dans les climats non tropicaux.
AHB2 Instruction Manual
Rev G
Page 38
Appendix
A Radical Approach to Power Amplification
The performance of the AHB2 would not have been achievable without taking a radical approach to
power amplification. In many ways, the AHB2 is a complete 180 degree departure from traditional
high-end amplifier designs.





AHB™ Amplifier – This unique amplifier uses THX-patented AAA(TM) (Achromatic Audio
Amplifier) technology to achieve high efficiency and vanishingly low distortion. The AHB2
combines class-H, and class-AB amplifier technologies with feed-forward error correction.
Feed-Forward Error Correction - Each channel of the AHB2 is equipped with a main
amplifier and an ultra-clean low-power auxiliary error-correction amplifier. The main classAB amplifier provides the bulk of the power while the auxiliary amplifier provides a lowpower error-correction signal. These amplifiers are combined to create a near-perfect null of
all distortion components. The AHB2's patented feed-forward error-correction system is
much more effective than traditional feedback error-correction systems. Distortion does not
change with loading, and does not rise near maximum output. Difficult loads are driven with
near-perfect clarity. Low-level musical details are delivered without the masking effects of
crossover distortion. The AHB2 is virtually distortion free at low levels, at maximum output,
and everywhere in between. Overall, the distortion produced by the AHB2 is so low, that it
approaches or exceeds the measurement limits of some of the finest audio test systems.
Error-Correction Amplifier - The error-correction amplifier is a small ultra-clean amplifier
that feeds a correction signal forward to the main output. The correction amplifier actively
drives the output while the main output devices are transitioning between push and pull
states. The correction amplifier actively suppresses distortion products that would normally
occur in a class-AB output stage. This feed-forward system is much more effective than
traditional feedback networks. Feedback systems attempt to correct errors after they
happen. In contrast, feed-forward systems can prevent errors from occurring.
Low-Bias Class-AB Main Amplifier - Class-AB output stages always produce "crossover
distortion" whenever the push-pull output drivers change state. Precise bias control is
usually required to minimize this crossover distortion. Traditional feedback networks have
difficulty correcting the transients caused by push-pull crossover transitions. However, the
THX patented feed-forward error-correction system has the speed and precision necessary
to virtually eliminate all traces of crossover distortion. With this feed-forward system, bias
currents have no significant impact on the distortion at the output of the amplifier. This
topology provides the freedom to conserve power by setting unusually low bias currents.
The AHB2 uses very low bias currents but achieves vanishingly low distortion - even under
heavy loading.
Class-H Tracking Rails - Multiple power supply rails (class-G), and tracking power supply
rails (class-H), can improve the efficiency of a class-AB amplifier. The AHB2 uses a lower
fixed rail and an upper class-H tracking rail. The improved efficiency provided by this
topology usually comes at the cost of increased distortion. For this reason, there are very
few amplifiers that use multiple supply rails. In a traditional feedback design, every rail
switch point adds another layer of crossover distortion. In contrast, the feed-forward error
correction used in the AHB2 is so effective that multiple rails can be added without
incurring any distortion penalty.
AHB2 Instruction Manual
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Page 39






Low Gain – The AHB2 has a low gain setting that optimizes the gain structure of
professional monitoring systems. Maximum rated output is reached at an input signal level
of 22 dBu. This places the upstream equipment in an ideal operating range to maximize the
SNR of the monitoring chain. Most power amplifiers have far too much gain, and this
degrades noise performance of the overall system. To provide compatibility with lower input
signal levels, the AHB2 has an ultra low-noise input amplifier with a 3-prosition gain switch.
The upper two settings boost the gain to allow direct interfacing with Hi-Fi components that
typically operate at lower signal levels than those produced by professional components.
Passive Cooling – The sonic performance of the AHB2 would be impossible to appreciate
if it had a motor-driven fan. There are no noise-generating fans to detract from the total
silence of the AHB2. Experience every detail of your favorite recordings without the
masking effects of fan noise.
Resonant Switch-Mode Power Supply – Most high-end power amplifiers use unregulated
linear power supplies. The conventional wisdom is that linear supplies are electrically quieter
than switching supplies. Benchmark's research shows that this is a myth. Linear supplies
have transformers that operate at the AC mains frequency. The problem with these 50 to 60
Hz transformers is that they must be very large in order to supply the required power.
These large low-frequency transformers generate large stray magnetic fields that can
interfere with other nearby devices, and with the amplifier itself. The noise performance of
many traditional power amplifiers is limited by the amplitude of the AC line-related hum.
This hum is often magnetically induced and is very hard to eliminate. To solve these
problems, Benchmark now uses switching power supplies in all of its newer products.
Switching frequencies are set well above the audio band. More importantly, the high
switching frequency greatly reduces the size of the magnetic components and the
magnitude of the stray magnetic fields. Resonant switching is used in the AHB2 to minimize
switching noise. Resonant supplies switch at low voltage and low current and are much
quieter than traditional switching supplies.
Regulated Power Supply - Audio amplifiers usually use unregulated supplies. The theory
is that the amplifier can produce higher peak output power for a given power supply size.
Linear regulation would throw away power that could be delivered to the output devices.
Benchmark's move to switching supplies changes the efficiency equations. Switching
supplies can produce a regulated output without wasting power and without creating
unwanted heat. A further advantage of regulation is that the output voltage is not a function
of AC line voltage, prior audio content, or speaker loading. The switching supply in the
AHB2 responds to bass frequencies, maintains a constant low-ripple output voltage, and
delivers very predictable output power.
Low Stored Energy - Most audio power amplifiers rely on a bank of large capacitors for
energy storage. These capacitors remove some of the ripple produced by an unregulated
linear supply, and help reduce supply sag in order to maintain a high output level
immediately following musical peaks. Unfortunately, these capacitors also slow down the
recovery from voltage sag due to peak loading. Benchmark's approach is to nearly eliminate
all storage after the power supply. The power supply regulation takes the place of energy
storage, responds quickly to peak loading, maintains very low ripple voltage, and provides
immunity to AC line-voltage fluctuations.
Digital Protection Systems - The AHB2 has a digital control system that monitors all of
the critical functions in order to provide comprehensive protection from overload and fault
conditions. Many of these systems do not exist in traditional designs.
AHB2 Instruction Manual
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Page 40

NL4 SpeakON Output Jacks - SpeakON connectors are well-accepted in high-power proaudio applications, but are nearly unknown in high-end Hi-Fi applications. Our tests show
that these robust connectors provide a much more reliable connection than the binding
posts, spade lugs, pins, and banana plugs used with traditional Hi-Fi amplifiers. Distortion is
measurably lower when using NL4 connectors. These connectors provide a very reliable,
low-impedance connection. Furthermore, they are polarized and fully insulated to protect
against short circuits, polarity reversals, and shock hazards. Benchmark recognizes that the
Hi-Fi industry is slow to embrace new ideas, so we have provided traditional binding posts
wired in parallel to the NL4 jacks. But, for the highest performance, we recommend using
the NL4 jacks. The jacks accept NL4 or NL2 plugs.
In summary, Benchmark has taken a radical approach to audio amplification, has leveraged
patented technologies (licensed from THX Ltd.), and has reversed many common practices. The
result is an amplifier that is significantly quieter, cleaner, smaller, and more efficient than any
traditional design. There is nothing ordinary about the Benchmark AHB2.
AHB2 Instruction Manual
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Copyright © 2014
Benchmark Media Systems, Inc.
All rights reserved.
Benchmark Media Systems, Inc.
203 East Hampton Place, STE 2
Syracuse, NY 13206-1633
USA
PHONE: +1-315-437-6300
FAX:
+1-315-437-8119
www.benchmarkmedia.com
AHB2 Instruction Manual
Rev G
Page 42
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