By Alan Silver President, Connoisseur Society, Inc. New York, NY
Philips of Japan was the customer, Jazz pianist John Lewis the artist.
"In 1984 I was offered the opportunity to record the legendary jazz pianist, John Lewis, in the 24 Preludes and Fugues from J.S. Bach's Well Tempered Clavier, Book One. It was a large assignment intended to take five years with completion scheduled for 1989. Each prelude was to be recorded exactly as written on solo piano and each fugue was arranged by John Lewis for piano, bass, guitar and varied combinations of strings. In addition, an interlude of jazz improvisation, played by Lewis, was to be integrated seamlessly into each prelude and fugue.
The record company was Philips of Japan, and they wanted me to match the solo piano sound they had heard on one of my Connoisseur Society recordings recorded earlier in a New York church. They ordered me to spare no expense in hall rental, engineering, or any other part of the master production. I hired a renowned engineer, his Schoeps microphones, and Studer mixer, and used the same hall as before. Kiyoshi "Boxman" Koyama, a noted producer of jazz recordings and writer on jazz subjects, was sent from Japan to New York as executive producer for Philips.
Koyama and Lewis were satisfied, and four years of fascinating music making followed, utilizing three different top-rated mixing desks and two engineers. But at the end of 1988, as preparations were being made for the final group of sessions in 1989, the engineering staff for the last several sessions was not available, and I was asked by Koyama to hire someone else. But in the preceding two years my wife, Patricia A. Duciaume, had become my engineering partner for all new Connoisseur Society records, and we had a full complement of digital recording equipment of our own, including a prized Benchmark MPS-420 microphone mixer. So I approached Koyama with the idea of having the last sessions be an all Connoisseur Society team. Koyama was concerned that our equipment didn't include a famous name-brand mixing board with its dozens of faders, solo buttons, E.Q., and pan pots. Also, he pointed out, we were customarily using more than 4 microphones for these sessions, and panning was essential.
Pat and I countered with a guarantee that we would provide pan pots and up to 8 mic capability. Koyama agreed, and we faced the next hurdle of getting more than 4 microphones into and out of our 4 channel Benchmark mixer. We consulted with Benchmark president and chief engineer, Allen Burdick, who recommended using two MPS-420 mixers. He offered to design an interface so that the two mixers could be ganged together, providing a maximum of 8 in and 2 out. Additionally, Burdick designed new circuitry for adding pan pots to the mixers, with the promise that they would not degrade the excellent noise and distortion characteristics we had come to admire.
The December 1989 session finally arrived, and as we set up, Koyama looked somewhat apprehensively at the two slim but elegant Benchmark mixers now replacing the large mixing desks of earlier sessions. But he politely said nothing and we began our work. After the first few playbacks, Koyama moved over to my chair and said with a pleased look that the sound was definitely the best of all the sessions since we began in 1984. It was cleaner and more transparent. But since we were using the same type of microphones and digital recorders he wondered if the improvement could be coming from the Benchmark mixers. I assured him that was the case.
Koyama is a sensitive man and I wondered if he was as enthusiastic as he said. The question was answered a few months later when he invited Pat, me, and our Benchmark mixers to record John Lewis again, this time in a new project for Polygram, Paris."
While this application note is now somewhat dated, the MPS-400 and the MPS-420 microphone preamplifier systems are not. We recently received high praise from one of Canada's top mixing engineers who had purchased a very highly regarded competitive preamplifier system, only to return it in favor of the Benchmark MPS-400. These systems are regarded by those who own and use them as the finest available.
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.