In this interview, John Siau shares a few thoughts about his career history and the history of Benchmark. He also discusses the importance of combining measurements with listening tests. He also some unique characteristics of the Benchmark A/D and D/A converters.
In the early 1980s John was involved with the early development of HDTV at the CBS Technology Center. This was about 15 years before regular HDTV broadcasts were available in most of the USA. It was during his time at CBS that John designed and built the very first device that was capable of digitally storing one full frame of HDTV video. Using the available technology, this required 6,144 1Kx1 DRAM chips running at maximum speed. These were packed into a 7-foot rack that drew 18 kW of power, quickly heating the room whenever it was running. This rack included 64 MHz ADCs and DACs and high-speed low-jitter clock circuits. This frame store provided asynchronous conversions between the otherwise incompatible NHK and CBS HDTV systems.
In 1985, John moved his young family back to his hometown, near Syracuse, NY. Here he designed analog and digital video circuits for the GE Talaria light valve projector. Five years later he started his own consulting business. During this time he designed a video DSP for the Talaria projector which greatly improved the image quality. Next he designed a karaoke circuit for Thompson Consumer Electronics. After that, he designed Benchmark's first digital product, the AD2004. This delivered state-of-the-art perfomance at 48 kHz with a bit depth of 20 bits. After completing the AD2004, John became a Benchmark employee, and eventually a stockholder. John has designed all of Benchmark's converters as well as many of their microphone preamplifiers, line preamplifiers, and headphone amplifiers. He also designed portions of the AHB2 power amplifier.
In this podcast, John discusses the importance of audio transparency, especially in the context of recording and mastering studios. He also makes a strong case for using transparent playback equipment in the home environment.
John discusses the importance of using a combination of measurements and listening tests. Almost 18 years ago, Benchmark discovered the intersample clipping problem in ASRC and sigma-delta converters through a series of listening tests. It was a year or two before they devised a test that would expose this problem. It was invisible to conventional audio tests, and according to these tests, it should not have been possible to hear the defects in the ASRC. Nevertheless, the team could clearly identify a problem in blind ABX tests. Once they identified the problem, John added 3 dB of digital headroom to the DAC2 converter and the problem was completely solved. 15 years later, most competing DACs still have intersample overload problems. This problem has persisted, because most test labs are not running the simple test that exposes this problem. In this interview, Soundstage! confirmed that they have begun testing for intersample clipping.
John goes on to discuss the importance of linear-phase brick-wall lowpass filters. He explains the problems that are introduced by other filters. Benchmark's has demonstrated that their filters preserve the analog waveshape through 16 or more generations of cascaded A/D and D/A conversions. Other filter designs change the waveshape on the first conversion. This is counterintuitive to those who look at simplistic time-domain square wave responses. According to John, waveform integrity can easily proven with cascaded conversions. This waveform integrity is delivered from every Benchmark A/D and D/A converter that Benchmark has built over the past 30 years.
When asked about the impact of tariffs, John responded by saying that he is in favor of tariffs. He feels that tariffs help level the playing field for USA manufacturers. For too long, our exports have been subjected to tariffs, while Chinese goods arrived without corresponding tariffs. He went on to say that Benchmark is deeply committed to keeping their manufacturing within the USA.
