The Audiophile 10 MHz Reference Master Clock
“It’s incredible how much this clock adds to the sound fidelity – you have to hear this yourself!” – Dr. Roland Dietl, Hifistatement
The Story of the REF 10
Currently available digital converters, master clocks, and audio re-clockers perform acceptably when reproducing or processing digital audio. Even so, we at MUTEC felt that existing solutions fall short of delivering the full potential of audio productions. In our commitment to advancing the state of the art and science we set out to investigate the possibilities to further enhance the performance of digital audio systems. To do so, we recruited one of Germany’s most renowned RF engineers to join our R&D team. Together we developed a master clock generator with a technical performance beyond what we thought could be possible. The effects of the technical performance were then verified by a group of experience audiophile beta testers to ensure that the high-end performance translates to best-in-class sound.
The final result of our extensive efforts is the REF 10: a superior 10 MHz reference master clock and our first Empyreal Class product combining uncompromising engineering with the beauty of simplicity and the utmost clock precision.
Debunking the “Atomic” Myth
Our research has shown that the high clock stability of so-called “atomic clocks” based on a rubidium or cesium oscillator is limited to the long-term time domain. This long-term stability refers to the amount the absolute clock frequency (10 MHz, or 10 million cycles per second, in this case) drifts over time. While this long-term stability may be useful for some telecommunications applications, it is essentially irrelevant for digital audio purposes. Ultimately, it is the timing from one sample to another as a digital audio stream is transferred from one device to another that needs to be as precise as possible for best sound quality. Fluctuations in short-term stability are measured as jitter or phase-noise and are central to the audiophile performance of any digital audio device.
In contrast to these “atomic clocks” then, the REF 10 is engineered around MUTEC’s handcrafted, oven-controlled oscillator (OCXO) made in Germany, featuring highest clock stability in the time domain relevant for audiophile digital audio performance.
A well laid-out main power supply constitutes the basis for exceptional high-end products. To meet this requirement, we specifically designed for the REF 10 a dual linear power supply based on a German made toroidal transformer. It provides a dedicated transformer winding for the sensitive OCXO that is completely isolated form the surrounding circuit. Networks of lowest-ESR (equivalent series resistance) capacitors made by Panasonic ensure best interference suppression for the supply voltages. Hereafter, sub-Hz optimized, lowest-noise voltage sources arranged in multiple stages independently supply every part of the circuit to avoid mutual interference. However, for the heart of the REF 10, MUTEC’s handcrafted OCXO, we had to go even further. We developed a dedicated power source of such incredibly low noise that even our engineers themselves were amazed by the noise figures and the resulting oscillator performance we ultimately achieved. Consequently, we then developed unique ultra-low noise clock distribution and amplification circuits, which successfully transfer the oscillator’s reference signal to the REF 10’s eight outputs with virtually no losses.
Phase noise of the REF 10 as a function of frequency
Based on our knowledge of the importance of a clock signal’s rise time (steepness of the edge) for the audio performance, we chose a very high slew-rate, lowest ripple square wave signal for the REF 10. In contrast to the low slew-rate sine wave signals used by competing brands, this leads to superior lock precision and therefor minimized jitter at the receiving end. As a result, connected devices like DACs (D/A converters) and audio clocks will sound even better.
The exceptionally high slew-rate, lowest ripple square wave signal of the REF 10
An often discussed topic among audiophiles are the negative influences of RF (radio-frequency) interference in digital audio. In order to shield the REF 10 from such RFI and other interference we are placing the circuit boards in a 1.5 mm thick steel enclosure, which isolates the sensitive electronics from outside electrical disturbances. We intentionally refrained from using an aluminum case popular with other manufacturers. An aluminum case would perhaps have lent a more esoteric look to the REF 10, but it would have seriously degraded the shielding characteristics allowing RF interference to directly increase noise and jitter of the clock signal.
RF interference can also enter the circuitry via the mains power connection. To avoid an power line interference as best as possible, we have equipped the REF 10 with one of the best premium, brand-name power entry modules currently available. This module offers enhanced low frequency filtering and superior EMI immunity. As part of its mechanical design there are no open, unfiltered power cables inside the unit unlike many other products on the market.
To especially minimize the susceptibility to hum caused by ground loops we have designed the REF 10 with galvanically isolated output stages. Every BNC reference clock output can be switched off individually so that only the currently desired outputs for a given setup need to be active. This feature further adds to our measures to keep mutual interference and system load as low as possible.
One Clock to Rule Them All
The REF 10 is the most flexible, most compatible 10 MHz clock on the market allowing you to spend less time worrying about integration and leaving you with more hours to enjoy blissful playback. Due to its ultra-low noise characteristics and its unrivaled flexibility the REF 10 can enhance the audio quality of compatible D/A converters (DACs) and re-clockers, music servers, and audio clocks to the highest possible level. It is the perfect match and ideal upgrade for MUTEC’s 10 MHz ready products like the MC‑3+ and MC‑3+USB Smart Clocks, as well as the iClock and iClock dp.
Eight simultaneous clock outputs at both 50 and 75 Ohms impedance allow you to use the REF 10 in combination with not just MUTEC products, but also 10 MHz compatible products by all other third-party manufacturers.
10 MHz Compatible Products Currently in Production:
Disclaimer: Compatibility of the REF 10 with the above listed products is assumed based on the specifications published by the respective manufacturers and subject to change. MUTEC is not liable for compatibility issues with third-party products operating outside of industry standards.
A Perfect Clock. Empyreal Sound
MUTEC’s Empyreal Class is our commitment to HiFi in its most sophisticated form. This series combines uncompromising engineering with the beauty of simplicity and utmost precision. Apart from exceptional sound performance these products feature a streamlined interface with fewer parameters and user-friendly operation. Just like any Empyreal Class product, the REF 10 is an investment in highest audio quality “Made in Germany” – an aspiration reflected by our extended manufacturer-guaranteed warranty of three years.
Retail Price £3295