For a standard device, the REF10 SE120 has undoubtedly outstanding measurement values. MUTEC is particularly proud of the fact that the development of the REF10 has already created a basis, from the power supply to the mainboard, which is so good that the brilliant values of the new oscillator used in the REF10 SE120 can actually be routed to the outputs without any loses in performance. Convincing technical justification or not – for me the question remains, whether the further improvement of the REF10 SE120 compared to the REF10 leads to an audible gain in sound quality. I am set on a hard head-to-head race between the two clocks, in which I will work out the finest differences between the two clock generators by switching back and forth several times between them.

Accordingly, I carefully prepare my listening test. As always, my tried and tested music server with XEON processor and Windows Server 2019 in Core Mode, tuned with Audiophile Optimizer, is used as the audio source. JPLAY Femto, MinimServer, JRiver26 and Roon Core are installed on the server as music management software. My two cascaded MUTEC MC3+USB are interconnected on the USB path to my PS Audio DirectStream DAC and are to draw their clock from either the REF10 or the REF10 SE120.

I prescribe the two REF10 clocks and the two MUTEC MC3+USB a warm-up period of several days. The clock generators are placed upside down on the shelf, that means with their rears facing forward, in order to be able to switch the cables between the devices as quickly as possible. MUTEC kindly supplied two matching, identical cables with 75Ω specification out of their own production. The right cable with the correct termination impedance is eminently important at a clock rate of 10 Megahertz. Mismatches can ruin everything. I advise against exotic cables without exact specifications at this critical point. All clock outputs that are not needed are switched off with the rotary knob on the front panel to reduce unnecessary interferences as far as possible. On both of my MUTEC MC3+USB the operating mode "externally referenced re-clocking mode" is set. Therefore, the two green LEDs "EXTERN" and "RE-CLK" light up under "Mode" and under "Status” the two upper blue LEDs "MAIN REF" and "RE-CLK REF". To be absolutely sure, I first play some music and remove the clock cables for test purposes. The two MUTEC MC3+USB don't make a sound anymore and I am sure that the clock is really set by the REF10.