Nowadays, USB is the most common interface to transfer digital audio data from a PC or a special audio server to an audio device, at least when it comes to consumer audio at home. As simple as the USB connection is in its handling, it is so difficult to come to grips with the sonics. Exactly at this point, the MUTEC MC-3+ Smart Clock USB enters the game.

The MC-3+USB is a rather inconspicuous little box from the Berlin-based company MUTEC, a leading manufacturer of high-quality A/V studio clocks, audio re-clockers, interfaces, format converters and signal distributors for professional applications. Though professional audio equipment is rather rare in domestic high-end systems, it is always worthwhile to think outside the box.

From a sonic point of view, computer-based music sources offer a rather inadequate environment for audiophile music enjoyment. Due to their construction, they operate with high clock rates while they keep a variety of processes running parallel to the music reproduction that create a wide spectrum of high-frequency interference of all kinds. The MC-3+USB is equipped with a special USB interface to minimize these unavoidable interferences and to prevent the sensitive digital-to-analogue conversion process from being adversely affected. It is completely galvanically isolated from the rest of the device, operating with its own ultra-low noise audio clock oscillators, which are fed by a carefully designed power supply consisting of a pre-regulator with a downstream main regulator. The MC-3+USB thereby acts as an isolator between the audio computer and the subsequent digital signal path. According to MUTEC, "interferences from the USB data stream can be suppressed as far as possible, resulting in an almost interference immune behaviour of the USB interface towards the connected PC, laptop or music server."

In the subsequent re-clocking unit, the digital audio signal is freed from interferences caused by a computer connected via USB and is then re-clocked under optimal conditions. For this purpose, the clock data contained in the incoming signal are first completely removed and then replaced by the clock data of the proprietary internal high-precision clock. The clock generation and its distribution are undoubtedly core competencies of MUTEC. The MC-3+USB uses a high-precision low-jitter clock generator with an extremely high system clock of one gigahertz. I will spare you further technical details at this point but here is what is important: the signal present at the MC-3+USB’s output provides an optimal clock quality and the re-clocking is completely bit-transparent. It is particularly important in studio environments that this clock signal can be passed to other devices via four clock outputs at the rear panel. At the end of my article, I will revisit this aspect.