The Mutec MC-3+ USB is a piece of pro or semi-pro gear from Germany that has been used a lot in studios and mobile recordings and is, more recently, gaining a reputation in the hi-fi market for its excellent performance.  It's a smallish box with a lot of LEDs and selectable modes, giving away its pro origins.  You need to have some understanding of what it's doing in order to set it up, but once done you can forget about it and even mute all the LEDs except the Lock light.

Essentially, when used in a hi-fi system, the MC-3 is a standards converter and reclocker.  Other features exist, such as a master clock output and clock multiplication, but I won't discuss them here.

Standards Conversion
The MC-3+ USB will accept USB (the reason for this model) and S/PDIF in AES, co-ax or optical formats.  There is an MC-3 without USB input available.  It will output to S/PDIF in AES, co-ax or optical formats.  I am using it with USB input from my streamer, outputting to AES format for my DAC.

Reclocking
The raison d'etre of this device is to accept a digital signal from the USB input, strip out all the poor quality timing and noise (something that computer-sourced USB is notorious for) and add in a clock from its own internal highly accurate and stable master clock.  If you have never heard reclocking a digital signal before, it will quickly put paid to any silly notion that 'bits are bits' and that any digital stream will suffice.  Put this baby in place and set it to reclock and your jaw (like mine the first time I heard it) is likely to hit the deck.

The MC-3+ USB comes with its own internal mains powered SMPS power supply.  In standard form, it's still a really superb performer.  However, it does benefit further from running from 5V DC and disabling the internal power supply.  I've had mine modified for external power and you can see the side entry cable feeding it in the photo below.  I'm using my Coherent supercap power supply.  It can still be powered by mains should I wish to use it in other systems.



So what does the MC-3+ USB do to justify its price?  There are two key aspects that are immediately noticeable, together with a general upgrade in sound quality in every aspect of musical performance.  The first is soundstage: the air and space in a recording, giving away the sound of the venue, revealing use of reverb, defining the position of the performers in space, changing a drum, say, from a dry instrument to one that affects and is affected by the room it's in, are all improved.  Soundstage width, height and depth are all larger than before.  Performers are better defined in space and vocals become better focussed and more realistically sized.

The second immediate area of improvement is in the bass.  Thought you had deep and powerful bass before?  Connect the MC-3+ USB into your system and the bass tightens noticeably, deep notes become easier to identify and follow, bass acquires texture so that a guitar note sounds quite different from an organ note, and the experience becomes even more visceral.  This in turn aids dynamics and scale, the whole performance taking a sizeable step-up in palpability and immediacy.  The line between studio and live performances starts to blend as some performances I had thought of as dry studio constructs actually have venue sound, even if they are multi-track creations.

Other aspects of system improvement are all the filigree details that come through the mix and the incredible dynamic swings and ebb-and-flow, creating a vibrant sense of excitement.

It's very difficult to impart more about this device unless you can hear it for yourself.  Even giving musical examples is difficult as I have learned that we each, as TAS members, like such different music.  I am reasonably certain, though, that if you have a digital system that can accommodate this unit inserted into the stream, you are likely to be very surprised and delighted at what it does for your musical enjoyment.

Bits, most certainly, are not just bits!