Variable-pitch features add versatility to CD players. Unfortunately, these features usually create jitter problems. Benchmark’s UltraLock™ jitter-attenuation system provides a unique solution that is fully compatible with variable-pitch transports.
The Purpose of the Variable Pitch Feature
Variable pitch is a popular feature on professional and semi-professional CD players. The variable pitch can be used to vary the tempo of the music by as much as +/- 15% on many players. In DJ applications the pitch control can be used as a bend control, or for tempo or pitch matching when fading from one song to the next. In live sound applications, small pitch adjustments can allow mixing of CD accompaniments with live instruments where the tuning of the live instruments may differ slightly from the recording. Dance groups often practice new performances at a reduced tempo when they are learning a new choreography. These are just some of the applications for variable pitch, and it is easy to see why this has become such a popular feature on professional CD players.
Variable Pitch Causes High Jitter Levels
Unfortunately, the variable pitch circuitry almost always adds high levels of jitter to the output of the CD player. High jitter levels are often present even when the pitch control is set to “0”. Variable-pitch CD players use a master oscillator that can be pulled +/- 15% (or more) from the nominal sample rate. This oscillator usually has much higher jitter than the fixed-frequency crystal oscillator used in non-variable pitch players. Users of professional CD players expect high performance from these premium-priced machines, but these machines often under-perform because of jitter problems. The jitter performance of most professional players is not specified and consequently it is very hard to make an intelligent decision when selecting a player. Users who don’t need variable pitch will discover that it is very difficult to find a professional transport that does not have a variable-pitch feature.
Benchmark D/A Converters Remove the Jitter
The Benchmark DAC1 and DAC2 family of converters offers a unique solution to the jitter produced by variable-pitch machines. DAC1 converters use Benchmark’s proprietary UltraLock™ jitter-attenuation system. DAC2 converters feature Benchmark new UltraLock2™ jitter-attenuation. Both systems remove virtually all of the jitter on any digital input signal.
Benchmark D/A Converters Lock to Any Sample Rate
Variable pitch systems change the digital sample rate by as much as +/- 15% in order to shift the pitch of the music. This means that most external converters will not operate if the variable pitch feature is activated. In contrast, Benchmark DAC1 and DAC2 converters accept any input frequency between 24 and 195 kHz and are fully compatible with variable-pitch features. Most competing systems are restricted to the standard sample rates (44.1, 48, 88.2, 96, 176.4, and 192 kHz). Any slight deviation (+/- 0.005%) from these frequencies will cause most competing systems to lose lock and/or lose their ability to attenuate jitter. Competing systems that can accept non-standard rates usually have little or no jitter attenuation. In contrast, the Benchmark systems are frequency agile and jitter immune.
A Digital Connection is Required
The DAC1 or DAC2 must be connected to a digital output from the CD player. Fortunately, most professional CD players have digital outputs, and in most cases, these outputs remain active over the entire pitch control range. When this is the case, the DAC1 or DAC2 bypass all of the analog circuitry in the player, removing the jitter, and providing mastering-quality balanced and unbalanced analog outputs. A DAC1 or DAC2 converter will provide a very significant upgrade to any CD player that is equipped with a digital output. This upgrade can be even more significant when performance of the stock player is degraded by the presence of a variable-pitch circuit.
UltraLock™ and UltraLock2™ remove the problems created by variable-pitch circuits without restricting the useful range of the pitch-variation feature.
At the 2023 AXPONA show in Chicago, I had the opportunity to see and hear the Hill Plasmatronics tweeter. I also had the great pleasure of meeting Dr. Alan Hill, the physicist who invented this unique device.
The plasma driver has no moving parts and no diaphragm. Sound is emitted directly from the thermal expansion and contraction of an electrically sustained plasma. The plasma is generated within a stream of helium gas. In the demonstration, there was a large helium tank on the floor with a sufficient supply for several hours of listening.
While a tank of helium, tubing, high voltage power supplies, and the smell of smoke may not be appropriate for every living room, this was absolutely the best thing I experienced at the show!
What happens when you ask ChatGPT to write a review?
I asked ChatGPT to review the Benchmark AHB2, and I was shocked at the results!
It turns out that ChatGPT wrote a review by gleaning information from the many publicly available reviews of the AHB2. I recognized phases and sequences of words that had appeared in prior reviews, and yet the text was new, original, and well written. The ChatGPT review seemed to summarize the collective impressions of the reviewers without directly quoting any particular reviewer.
It should be possible to ask ChatGPT to write a review on any well-known product and the result will be an AI-generated review that reflects the collective opinions of many human reviewers.
These AI-generated reviews may be more useful than traditional search results!
If I am not mistaken, ChatGPT seems to have golden ears!
Here is my dialog with ChatGPT:
Write a review of the Benchmark AHB2 complete with listening impressions.
Title: Unleashing Sonic Purity: A Review of the Benchmark AHB2 Amplifier
Introduction: The Benchmark AHB2 amplifier has gained a reputation for its exceptional audio performance and unwavering dedication to sonic purity. In this review, we delve into the heart of this powerhouse amplifier, exploring its features, design, and most importantly, the listening impressions it evokes...
Today, Benchmark's John Siau and OpenAI's ChatGPT had a conversation about star-quad cables. It turns out that ChatGPT got quite a few things wrong, but learned quickly when these errors were pointed out by John Siau.
ChatGPT is quick to recognize mistakes, and quick to provide detailed corrections. In each of the first few corrections, additional errors were made. As each of these were pointed out, ChatGPT began to provide accurate information.
Here is my conversation with ChatGPT:
How do star-quad cables reject interference?
Star-quad cables are designed to provide improved rejection of ...