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.
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.
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.
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.
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.
Front Panel Front Panel Layout Left to Right: 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 Rev G Page 7
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: 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-Pos
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Mechanical Drawings Dimensions AHB2 Instruction Manual Rev G Page 24
Rack-Mount Dimensions AHB2 Instruction Manual Rev G 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.
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.
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.
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.
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.
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.
CE Certificate of Conformity AHB2 Instruction Manual Rev G 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
