The Benchmark AHB2 power amplifier is named in honor of Benchmark's founder, Allen H. Burdick. Allen had a life-long passion for audio, and became one of the leading innovators in the pro-audio industry.
Allen's business ventures began in 1983 as "Benchmark Sound Company" where he operated from his garage in Dallas, Texas. He surrounded himself with a staff that shared his passion for achieving new audio performance "benchmarks". Benchmark's first product was a large mixing console for television and radio broadcast applications. In 1985, Allen changed the business name to Benchmark Media Systems, Inc., and relocated to a facility in his hometown of Syracuse, New York. By this time Benchmark was manufacturing the DA101 audio distribution amplifier for television studios. Allen's DA101 was a 40 W power amplifier card with astonishing specifications. It had a 160 kHz bandwidth, and a dynamic range of 130 dB. The DA101 was designed to distribute line-level audio through extensive distribution networks. Television networks often require many cascaded distribution amplifiers, and this places extraordinary demands on the performance of each individual amplifier. Allen's DA101 revolutionized audio distribution in the era of analog TV. Allen was a perfectionist and a prolific engineer.
Allen retired in 2006 due to health issues, but Benchmark continued to develop new products under the direction of John Siau. Allen's DA101 was never marketed as a power amplifier, but it became Benchmark's amplifier of choice for critical listening tests during the development of Benchmark's digital products. The recent development of the DAC2 converter family highlighted the need for a power amplifier that could match the performance of the converter, and Benchmark began an amplifier project that we code-named "PA2".
In many ways, Allen's DA101 helped define the performance goals of the PA2 project. Early prototypes were evaluated against the DA101. Benchmark's performance goals were achieved through the use of two new patented topologies from THX, the application of good engineering, and a high level of cooperation between the engineering groups at both companies. The result is an amplifier that Allen would have been proud to call a "Benchmark".
On September 27, 2013, the "PA2" was ready to go into production, but we still didn't have a final name for the new amplifier. The faceplates were machined and finished but needed to be printed with the product name. I began thinking about the technology in the amplifier and how this could be incorporated into the name. The amplifier delivered class-A performance, had class-H tracking rails, and a class-AB output stage. It then struck me that the letters A, H, and B were Allen H. Burdick's initials. The initials A.H.B. can be found on most early Benchmark schematics. Instantly it was clear to me that the new amplifier should be named after the man who inspired it! I announced the name to my staff, and we placed the order for the printing. Less than an hour later we got a phone call with the sad news that Allen had passed away.
In loving memory of Allen H. Burdick (June 29, 1942 - September 27, 2013).
- John Siau
The Benchmark AHB2 power amplifier and HPA4 headphone amplifier both feature feed-forward error correction. This correction system is an important subset of the patented THX-AAA™ (Achromatic Audio Amplifier) technology. It is one of the systems that keeps these Benchmark amplifiers virtually distortion free when driving heavy loads. It is also the reason that these amplifiers can support 500 kHz bandwidths without risk of instability when driving reactive loads.
This paper explains the differences between feedback and feed-forward systems. As you read this paper, you will discover that you already understand the benefits of feed-forward correction because you use it instinctively to improve a feedback system commonly found in your automobile. If feed-forward correction can improve your driving experience, it may also improve your listening experience!
If you look at the back of any Benchmark product, you will find balanced XLR analog-audio connectors. As a convenience, we also provide unbalanced RCA connectors on many of our products. In all cases, the balanced interfaces will provide better performance.
We build our unbalanced interfaces to the same high standards as our balanced interfaces, but the laws of physics dictate that the balanced interfaces will provide better noise performance.
This application note explains the advantages of balanced interfaces.
Benchmark has introduced a new analog-to-analog volume control circuit that features a 256-step relay-controlled attenuator and a 16-step relay-controlled boost amplifier. The volume control has a +15 dB to -122 dB range in 0.5 dB steps and is a key component in the HPA4 Headphone / Line Amplifier.
Our goal was to produce an analog-to-analog volume control with the highest achievable transparency. We wanted to be able to place this volume control in front of our AHB2 power amplifier or in front of our THX-888 headphone amplifier board without diminishing the performance of either device. Our volume control would need to have lower distortion and lower noise than either of these amplifiers. Given the extraordinary performance of these THX-AAA amplifiers, this would not be an easy task!
This application note discusses the engineering decisions that went into the development of this new analog volume control circuit. The end result is a fully buffered volume control with a signal-to-noise ratio that exceeds 135 dB. THD measures better than the -125 dB (0.00006%) limits of our test equipment.