From the first watt to the last watt, no audio power amplifier offers lower noise or lower distortion than the Benchmark AHB2. Benchmark has raised the bar by introducing a new and revolutionary amplifier!
-Bascom King, BHK Labs
"It is one of the -- if not the -- quietest, most resolving amps I've heard. Time and again, without ever having intended to, I wound up hours deep in listening to the fringes of my music collection, thanks to the AHB2’s reference-level transparency and obscene athleticism."
- Hans Wetzel, SoundStage!
The AHB2 has been internationally recognized for its groundbreaking technology, performance, and transparent sound.
The AHB2 is the ideal match to the performance limits of High-Resolution-Audio (HRA) formats. Benchmark's AHB2 power amplifier delivers musical details without introducing the masking effects of amplifier noise and distortion. The dynamic range of the AHB2 is 132 dB, making it 10 to 30 dB quieter than some of the very best reference-quality power amplifiers.
The frequency response of the AHB2 extends beyond 200 kHz. With the AHB2, you will discover previously overlooked nuances, dynamics, and detail in your favorite recordings and experience the full potential of the latest high-resolution 24-bit PCM and 1-bit DSD audio formats.
The musical details and emotion captured on today's finest High-Resolution-Audio recordings can only be fully appreciated when every component in the signal chain is capable of true high-resolution performance. Power amplifiers are a weak link in most audio systems. Most power amplifiers are well matched to the limitations of the CD format, but they fall well short of the capabilities of high-resolution formats. In contrast, the revolutionary AHB2 was specifically designed to deliver true high-resolution performance.
The AHB2's extended frequency response, tight bass control, ultra low noise, and vanishingly low distortion are key parameters contributing to accurate reproduction of high-resolution musical recordings. Experience the full emotion and detail captured in your finest recordings:
- John Gatski, Everything Audio Network
-Greg Weaver, Enjoy the Music.com
- Barry Rudolph, Mix Magazine
- Barry Rudolph, Mix Magazine
"The transients were dead-on accurate — without the shrillness I often hear in bipolar amps. The AHB2’s sonic character is dynamic, open, with quick, taut bass — yet with the silky ease of the best tube amp. But tube amps don’t have the energy and speed in the transients, nor bass, that the Benchmark possesses."
"Like the Benchmark D/As and A/D, the company believes that great measurements correlate to great sound. In the case of the AHB2 I totally agree. I can’t wait to get two more for a full-high-end home cinema amp test in my big A/V room. For now, based on mostly stereo listening, it receives, with certainty, an Everything Audio Network Stellar Sound Award."
- John Gatski, Everything Audio Network
"The new Benchmark AHB2 is the result of considerable research and patents on its resultant circuitry. The intent was to make it an ultra low distortion design. I would have to say they succeeded as it is the lowest noise and distortion power amp I have measured and I have measured a LOT of power amps in my career."
- Bascom H. King, BHK Labs
Experience high resolution audio as you have never heard it before. The AHB2 is a ground-breaking product. Benchmark has leveraged patented technology from THX to create an amplifier that defines a whole new level of performance. No audio amplifier delivers lower noise or lower distortion.
"In today's world, where the advertising and self-promotion of nearly every new product coming to market claims to employ some exemplary breakthrough, and the term innovative is bandied about so freely that it seems to have lost any real meaning, Benchmark's AHB2 amplifier is a truly breakthrough, innovative design."
- Greg Weaver, Enjoy the Music.com
In a normal listening environment, a comfortable listening level is usually reached with only a few watts of audio power. With high-efficiency speakers, most of the audio may be delivered at less than one watt. In either case, the 1st few watts of power are some of the most important to the listening experience. Unfortunately, most amplifiers perform poorly in this low-power region. This is the region where the non-musical distortion caused by conventional class-AB push-pull output stages can rise to a high percentage of the audio level. Likewise, the dead-band distortion in a class-D amplifier can be problematic at these low output levels. The AHB2 does not have either of these problems. It behaves like a class-A amplifier in the low-power region. The AHB2 is virtually distortion-free in the critical first few watts.
Class-A amplifiers often perform poorly at high power levels. Likewise, class-D amplifiers often have slew-rate related distortion problems that show up at higher power levels. Class-AB amplifiers tend to do well at high levels, but usually show a gradual increase in distortion energy as the output increases. In contrast to these conventional designs, the AHB2 remains virtually distortion free to the last watt.
The frequency response of the AHB2 extends beyond 200 kHz, to deliver the ultrasonic detail and fast transients captured by high-resolution recordings. At the other end of the audio spectrum, the low-frequency response extends below 0.1 Hz, for solid well-controlled bass.
The extended frequency response delivers a nearly perfect impulse response, and a nearly perfect phase response, over the entire audio spectrum.
- Barry Rudolph, Mix Magazine
-Greg Weaver, Enjoy the Music.com
Other than loudspeakers, power amplifiers are usually the weakest link in the audio chain. Until now, high-resolution recording formats and converter technology have rapidly outpaced the development of audio power amplifiers. For example, Benchmark DAC2 D/A converters outperform most high-end power amplifiers by very significant margins.
Most power amplifiers limit system noise performance to the equivalent of a 16 to 18-bit digital system. The differences between 16-bit and 24-bit recordings cannot be experienced if the power amplifier can only deliver 16-bit noise performance. In most audio systems, the details captured by today's high-resolution 24-bit PCM systems are completely lost in a veil of amplifier noise and distortion.
Benchmark set out to build an amplifier that would deliver the full performance of their flagship 24-bit 192-kHz D/A converters. The AHB2 realizes this goal, and it is the first power amplifier that meets or exceeds the performance of the DAC2 D/A converter.
- Barry Rudolph, Mix Magazine, December 2014
Many loudspeakers have frequencies at which their impedance drops to levels that are much lower than the "nominal" impedance. The AHB2 drives these low impedance regions with ease. Loads as low as 2.2 Ohms can be cleanly driven to full output levels. Most power amplifiers produce higher levels of distortion when the load impedance decreases. In contrast, the feed-forward error correction system in the AHB2 prevents any increase in distortion. The AHB2 produces almost no measurable distortion at any rated load condition.
The AHB2 has a high damping factor that augments its extended low-end to deliver solid, well-controlled bass. This high damping factor also keeps the frequency response absolutely flat while driving speakers with large frequency-dependent impedance variations.
The AHB2 can deliver up to 18 A to each channel simultaneously. This robust drive current easily handles some of the most demanding loudspeakers. The AHB2 stays clean while delivering high current.
The AHB2 will never produce audible distortion, In most playback systems, the distortion produced by the AHB2 will never even reach the 0 dB SPL threshold of hearing. This means that the distortion could not be heard, even if it could be played while the music was muted.
The AHB2 allows you to escape the distortion limitations of classic amplifier topologies and enter the world of high-resolution audio playback.
"I very much enjoyed my time evaluating the Benchmark AHB2 amplifier and can heartily recommend it to those seeking one of the lowest distortion and lowest noise amplifiers on the planet—one that is very musically transparent and easy on the ears to boot."
- Frank Alles, Stereo Times
The AHB2 amplifier is radically different than traditional audio amplifiers. Two new THX-patented feed-forward error-correction technologies eliminate most sources of distortion. An unconventional power supply maintains tight regulation and low ripple while minimizing magnetic fields. A low-gain topology optimizes the gain staging between the D/A converter and the power amplifier while minimizing noise. Sophisticated shielding and star-quad signal distribution provide outstanding immunity to interference. A unique output stage incorporates class-H tracking power supply rails to improve efficiency. The result is that the cool-running AHB2 has a signal to noise ratio of 132 dB while distortion is at or below the measurement limits of the finest test equipment.
See John Siau's application note: "A Radical Approach to Power Amplification" for more details.
The AHB2 is the only amplifier that leverages the patented THX-AAA Technology™. This patented system reduces distortion to vanishingly low levels while enabling several power-saving techniques.
"The Benchmark AHB2 is a powerful and efficient amplifier with prodigious low levels of noise and distortion. The fact that it is also very musical and non-fatiguing, courtesy of THX’s patented AAA Technology™, is the icing on the cake. Benchmark Media and THX have a lot to be proud of for the development and implementation of the new technology the AHB2 represents."
- Frank Alles, Stereo Times
The AHB2 has a bipolar class-AB output stage that delivers high output current and low noise. The THX-AAA Technology™ provides accurate cancellation of zero-crossing errors, exceeding the performance of the best class-A amplifier.
Traditional class-AB amplifiers generate crossover distortion every time the push-pull output stage crosses 0 volts. This crossover distortion can be especially problematic at low playback levels.
In contrast, class-A amplifiers eliminate crossover distortion by keeping all output devices turned on at all times. This eliminates the push-pull crossover region and this eliminates crossover distortion. Unfortunately. this improvement comes at the expense of high power consumption, poor damping, and limited output power.
Traditional class-AB designs attempt to control distortion through the use of feedback. Unfortunately, these feedback systems have a limited ability to reduce the abrupt transients that are caused by output device crossover transitions. Feedback networks attempt to correct errors after they occur. In contrast, feed-forward networks can prevent errors before they occur.
The THX-AAA Technology™ includes an ultra-clean low-power error-correction amplifier that runs in parallel with the high-power main amplifier. The correction amplifier actively drives the output while the main output devices transition between push and pull states. Like a class-A amplifier, the AHB2 shows no signs of crossover distortion. The feed-forward system virtually eliminates the errors that would have been produced by the output devices in the main amplifier.
The THX-patented feed-forward error correction used in the AHB2 is so effective that biasing of the class-AB bipolar output devices can be reduced to unusually low levels. Benchmark has chosen to maintain a small bias current in the output stage, but this bias current is not critical to the distortion performance of the unit. The benefit of low bias current is that very little power is wasted as heat when the amplifier is idle. The AHB2 only draws 12 W when idle, and less than 1/2 W in standby.
The feed-forward error correction also allows the use of class-H tracking power supply rails without the usual distortion-performance penalty. These tracking rails significantly improve the overall efficiency of the amplifier while the error correction keeps distortion nearly nonexistent. The AHB2 rivals the efficiency of class-D amplifiers while exceeding the sonic performance of power-hungry class-A designs. Green never sounded so good!
Most high-quality power amplifiers have linear power supplies, large toroidal transformers, and large banks of energy-storage capacitors. These linear supplies are usually unregulated and the capacitors help to remove ripple produced by the audio and by the AC line. In contrast, the AHB2 uses a tightly regulated resonant switching power supply that includes a very fast control loop. This control loop responds to audio-frequency load changes and keeps the supply voltage constant without the use of a large bank of capacitors. This active regulation is much more effective than capacitive energy-storage. Consequently, the peak power output of the AHB2 does not vary with line voltage or audio loading. The power supply rails maintain a constant voltage during audio peaks.
The power supply in the AHB2 switches at frequencies that are well above audible frequencies. This eliminates mechanical hum while significantly reducing the strength of stray magnetic fields. For a given amount of power, magnetic field strength decreases as switching frequency increases. The lower field strengths also provide a significant reduction in size. High-frequency transformers and coils are also much smaller than line-frequency components. This size reduction contributes to the small physical size of the AHB2.
The switching power supply used in the AHB2 is a zero-voltage switching, resonant power converter. This means that the power devices in the supply switch near zero voltage and zero current, eliminating the large switching transients produced by conventional switching power supplies. The power supply in the AHB2 is actually much cleaner and quieter than a conventional linear supply.
The power supply In the AHB2 is well over 90% efficient, much more efficient than linear supplies. This means that little power is lost to heat.
The power-efficient AHB2 uses passive heat sinks to maintain cool operation. The AHB2 delivers high power without the need for fans. The unit runs cool, even when playing audio at full output levels. The absence of fan noise is absolutely essential in a high-resolution listening environment.
The precision balanced inputs on the AHB2 are equipped with low-noise input amplifiers. Benchmark considers balanced inputs essential in a true high-resolution system. If balanced sources are not available, Benchmark sells unbalanced to balanced adapter cables that extend a 3-wire balanced connection back to the unbalanced source connectors. These adapter cables provide many of the advantages of fully balanced interconnects while providing full compatibility with all unbalanced sources.
The AHB2 is a low-gain design. Maximum output is not reached until the balanced inputs reach +22 dBu. This is a much higher signal level than is used at the input of most power amplifiers. High interface signal levels are required to achieve the best possible system signal to noise ratio (SNR). Most power amplifiers have far too much gain and consequently they suffer from poor noise performance. The AHB2 is 10 dB to 30 dB quieter than some of the very best power amplifiers on the market. A rear-panel gain switch can be used to set the AHB2 at higher gain settings if necessary. The low-gain setting is designed to interface directly with Benchmark DAC2 converters and other professional audio products.
The AHB2 is equipped with high-quality binding posts, and SpeakON output connectors. The high-current SpeakON connectors are designed for heavy-duty commercial sound systems and provide much better electrical connections than binding posts. Benchmark highly recommends the use of the twist-lock SpeakON output connectors. We highly recommend the use of our top-quality professional-grade speaker cables.
The letters A, H, and B allude to the unique topology of the amplifier's output stage. The AHB2 combines class-AB, and class-H topologies using a feed-forward error correction system.
But there is much more to the story -
The initials A.H.B. can be found on many of the circuit diagrams of Benchmark's early products dating back as far as 1983. These are the initials of Benchmark's founder, Allen H. Burdick. He personally designed many of Benchmark's early products.
Allen had a life-long passion for audio, and he became one of the leading innovators in the pro-audio industry. The AHB2 is named in his memory.
1 kHz, < 0.0003 % THD+N
All speakers have variations in input impedance. Select loads based on nominal impedances not minimum impedances.
Rated output relative to output noise, inputs shorted
Output noise voltage, inputs shorted
Output noise power, inputs shorted
1 kHz, 80 kHz LPF, at full rated output into any rated load
1 kHz, 20 kHz LPF, at full rated output into any rated load
Detailed specifications and performance plots are available in the downloadable manual.