Mutec REF10 SE120 Reference Master Clock

The REF10 SE120 is a special version of the successful audiophile reference clock generator REF10 that we have further enhanced in terms of signal performance. The exceptional quality of the original REF10 has been confirmed many times since its launch in 2017 – in numerous reviews from specialized magazines and through enthusiastic user feedback. A clock generator from MUTEC significantly increases the quality of digital music playback, even and especially with demanding high‑end systems and studio installations. Because it provides the foundation for perfect signal processing in a digital audio chain: the extremely low‑noise reference clock.

The “tuning” variant REF10 SE120 outperforms the original model REF10 in this regard considerably. A clearly measurable advantage is the result of a special feature of the REF10 SE120: its much more elaborately manufactured and selected oven‑controlled quartz oscillator (OCXO). This oscillator is selected according to the strictest standards in test procedures lasting many hours with the help of exceptionally precise and expensive measuring technology. The use of such an outstanding oscillator is responsible for the fact that the REF10 SE120 from MUTEC currently delivers – to our knowledge – the lowest phase noise, respectively jitter values in the industry. This outstanding technical performance has a noticeable impact on the sonic result. Precision, transparency, spatiality and dynamics of the musical presentation reach an unprecedented level and will inspire you!

Like the proven REF10, the optimized REF10 SE120 is extremely flexible. Because of its versatile connectivity this MUTEC clock generator can be successfully integrated in a wide variety of configurations while maintaining an easy way of operation. If you want to maximize the sound potential of your compatible DA converter, music server or audio re‑clocker in every respect, you need the REF10 SE120 from MUTEC!

The Development towards the REF10 SE120

The great success of the well‑established MUTEC REF10 has proven the extremely positive, clearly audible influence such a meticulously developed reference clock generator has on the sonic performance of a digital audio system. Despite the worldwide praise of the device by users of all kinds, MUTEC is always driven by the same question: can we do even better?

The positive answer is available in the shape of the REF10 SE120. Because already during the development of the REF10 we noticed how extremely important the selection of the central clock oscillator is. Its quality determines the technical and consequently also the acoustic result of a reference clock generator to a considerable extent. That is why the renowned German developer of the REF10 has been appointed to help improving and optimizing the production processes around the new ultra‑low phase noise oscillator to make it successfully suitable for being the heart of the REF10 SE120.

The basis for this new oscillator is naturally a SC‑cut crystal material, but here it gets very elaborately selected especially with regard to the ultra‑low phase noise specifications to be achieved. After assembling and by using specialized and cost‑intensive measurement technology, the selection of the oscillators continues with three‑stage in‑depth measurements. Thus, after the last measurements individual specimens from large production quantities can be selected successfully as the best oscillators for use in a REF10 SE120.

These oscillators reliably offer phase noise values of <‑120 dBc measured at 1 Hz offset from the carrier frequency of 10 MHz. Values like this have never been reached before! Such technical performance also positively influences the phase noise at audio-relevant measuring intervals of 10 Hz and 100 Hz. As a result, a REF10 SE120 offers uniquely low jitter measured values of an average of <15 fs in the crucial measuring range between 1-100 Hz!

Exclusive + Limited

Naturally, only a small number of oscillators complete our demanding test course for selection successfully. That is why the REF10 SE120 will only be available in small batches. The lucky owners of an exclusive REF10 SE120 will gain a fascinating experience. The musical reproduction quality of their high-class audio setup fuelled by this special edition of the REF10 rises significantly – especially in the areas of precision, transparency, spatiality and dynamics. The REF10 SE120 is currently not only the absolute top product in MUTEC’s Empyreal Class, but also claiming the industry-leading position in the field of audiophile reference clock generators.

Stability Factor vs The Myth of the Atomic Clock

The so-called “atomic clock” is generally regarded as a prime example of extraordinary frequency precision. However, our research has shown that the high clock stability of atomic clocks based on a rubidium or caesium 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. In fact, the accuracy of the time interval from one sample to the next sample determines the sound quality, i.e. the stability viewed in a very short time range. Changes in this short-term stability are usually measured as jitter or phase noise. These are decisive for the sound quality of all digital audio devices.

In contrast to these atomic clocks the REF10 SE120 is engineered around MUTEC’s extremely elaborately selected, handcrafted, oven-controlled quartz oscillator (OCXO) made in Germany. This OCXO offers a standard-setting frequency stability in the time domain relevant for audiophile music playback.

Perfect Conditions

MUTEC has created an optimal environment for the exclusive OCXO within the REF10SE120.

It starts in an essential segment for every high-end component: the well designed main power supply. Therefore, a double linear power supply is used, based on a toroidal transformer made in Germany. 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 prestigious manufactures 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.

For the heart of the REF10 SE120, the handcrafted OCXO, we went even further by developing a voltage source with exceptionally low noise. In line with this, extremely low-noise clock distribution and amplification circuits ensure that the reference signal of the quartz oscillator in the audio-relevant measuring range of 1-100 Hz distance from the carrier frequency (10 MHz) is transported loss-free (!) to the eight outputs of the REF10 SE120.

Phase noise of the REF10 SE120 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 digital audio performance, the REF10 SE120 delivers square-wave signals with very high slew rate and lowest ripple at the outputs.

In contrast to the low slew-rate sine wave signals used by competing brands, this leads to superior lock precision in terms of speed and stability and therefore minimized jitter at the receiving end. This fact is i. e. largely responsible for the sound quality improvement of connected DACs and audio clock generators.

The exceptionally high slew-rate, lowest ripple square wave signal of the REF10 SE120

Steel Shielding

An often discussed topic among audiophiles is the negative influence of RF (radio-frequency) interference in digital audio playback. In order to shield the REF10 SE120 from such RFI and other interference we are placing the circuit boards in a 1.5 mm thick steel enclosure. In contrast to the commonly used aluminum housings, the shielding of the electronics and thus the insulation against external disturbances is significantly improved hereby. Therefore, any external high-frequency interference does not have a detrimental effect on the noise and jitter freedom of the generated clock signals.

Mains Filter

RF interference can also enter the circuitry via the mains power connection. To avoid a power line interference as best as possible, we have equipped the REF10 SE120 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. Another aspect where the REF10 SE120 distinguishes itself from many other products on the market.

Galvanic Insulation

In order to minimize the susceptibility to hum caused by ground loops all output stages of the REF10 SE120 are galvanically isolated. Each BNC reference clock output can be switched on and off individually, so that only the required outputs have to be active. This special feature of the REF10 SE120 also helps to minimize high frequency interference as much as possible.

Reference Clock Reference

The REF10 SE120 is a reference clock that fills the term “reference” with meaning in two ways. First, because of its function: it generates an optimized master clock to which all subsequent devices in the digital audio chain refer to. Second, because of its quality: as the top product from MUTEC, the REF10 SE120 also represents a new standard in this specific category of audio components. This master clock generator sets new peak marks in the key areas of phase noise, respectively jitter.

The amazing sound performance – based on superior technology – can be easily realized in many different audio setups. Because the REF10 SE120 is straightforward and extremely flexible to use. You do not have to worry about system integration at all – instead, you can fully enjoy the best possible music playback straight away. With the help of a REF10 SE120 the audiophile sound quality of compatible D/A converters, music servers and audio re-clockers will be increased to the highest possible level.

The REF10 SE120 is the perfect match for devices with a 10 MHz input, such as MUTEC’s MC3+ and MC3+USB Smart Clocks as well as the iClock and iClock dp.

Eight simultaneous available clock outputs at both 50 Ω and 75 Ω impedance allow you to use the REF10 SE120 in combination with not just MUTEC products, but also 10 MHz compatible components by other third-party manufacturers.

Interfaces

• 2 x 10 MHz reference clock BNC output, 50 Ω terminated, unbalanced
• 6 x 10 MHz reference clock BNC output, 75 Ω terminated, unbalanced

Signal Format of all Clock Outputs

• Square wave, 10.000 MHz, 2 Vpp, 50:50 duty cycle

Clock Generation

• Type: 10.000 MHz ultra-low noise oven-controlled crystal oscillator
• FQ stability when shipped: < +/-0.01 ppm
• FQ stability vs. temperature range: < +/-0.01 ppm within -20 °C to +70 °C (-4 °F to +158 °F)
• Short term stability (Allan deviation) at Tau = 1 s: 2.5 x 10-13 (typically)
• Aging after 30 days operation:
  < +/-0.0002 ppm (per day),
  < +/-0.03 ppm (1st year),
  < +/-0.2 ppm (10 years)
• Warm-up time at +25 °C (+77 °F) : <5 min

Phase Noise, Measured at REF10 SE120’s Outputs

Phase noise of the REF10 SE120 as a function of frequency

Jitter Performance, Measured at REF10 SE120’s Outputs

1-100 Hz: ≈ 15 fs

Jitter performance of the REF10 SE120

Disclaimer: All measurement figures represent average values. Minor production related deviations will be expected.

Power Supply

• Type: internal dual linear power supply
• Input Voltage: 90-125 V / 200-240 V, 50-60 Hz
• Power consumption: 12 W during oscillator warm-up, 8 W nominal operation

Mechanical Details

• Cover size/material/color: 196 x 84 x 300 mm (W x H x D, without connectors and case feet), 1,5 mm steel, black powder-coated
• Front panel size/material/surface/color: 198 x 88 x 8 mm (W x H x D), aluminium, anodized incl. anodic printing or silk screening, aluminium- or black-colored
• Weight: approx. 4350 g (9 lb, 9.5 oz)

10 MHz Compatible Products Currently in Production:

Disclaimer: Compatibility of the REF10 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.

With MUTEC to “heavenly” sound!

Within the Empyreal Audio Class series, MUTEC offers special digital audio devices dedicated to the demanding users of top-quality hi-fi stereo systems. These unique products benefit from MUTEC’s decades of expertise in the field of professional studio technology. This knowledge flows into the development of audiophile tools that have outstanding sonic abilities.

A MUTEC Empyreal Audio Class component always focuses on features most relevant for authentic sound reproduction in a high-end audio system. Decorative accessories or cluttered front plates are alien to these devices. Therefore, the operation is designed to be user-friendly and convenient. On the outside, the series is characterized by functionalism combined with simple elegance. Internally, the highest level of technical precision can be found based on best available materials. Both aspects support the conceptual goal of the Empyreal Audio Class: pure concentration on what is technically essential.

All MUTEC devices of the Empyreal Audio Class series represent long-term investment because of their highest quality at all levels – of course “Made In Germany”.

Features

• 10 MHz reference master clock generator with ultimately low phase noise of ‑120 dBc at 1 Hz
• Improves and enhances compatible DACs, audio re‑clockers, music servers and master clocks
• Engineered around an elaborately manufactured and selected OCXO made in Germany with outstanding low noise
• Generates a very high slew‑rate square wave signal for superior lock precision
• Provides simultaneous reference outputs with 50 Ω and 75 Ω impedance for maximum compatibility with audio components by other manufacturers
• Eight galvanically isolated, individually switchable BNC clock outputs
• Sub‑Hz optimized, lowest noise power supply for every circuit section
• Integrated highest quality international linear power supply
• Highly efficient power line filtering
• Intuitive user interface with noble appearance
• Rack‑mountable for studio use with optional mounting brackets (2 RU)

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