Mutec MC-3+

[iago]

I would rather compare Paul Pang USB with Uptone Regen, because both aim to deliver an immaculate USB signal at their respective output. The MC-3+ re-clocks a S/PDIF (or AES3) signal, the MC-3+ USB adds a USB converter. Which is the better solution (USB or S/PDIF) largely depends on your DAC ...

[iago]

Some people even use multiple re-clocking devices in a chain. The re-clocking can never remove every artifact, and multiple devices have a cumulative effect (something like a filter chain). I use a S/PDIF converter, which applies it's own clock to the signal, and in addition a Mutec MC-3+ before passing the signal into the DAC. The addition is noticeable, but less than the initial introduction of the S/PDIF converter. Signal reconditioning inside the DAC also has an influence on the result: less expensive DACs benefit more from re-clocking.

[iago]

I just checked my power supply: additional power consumption with Mutec plugged in is approximately 2W, which should correspond to a current draw of 0,35A from the device.

[iago]

Another question for Julian (enjoy your holiday, by the way):

 

What is the interaction of the different MODE settings with the MC-3+USB's performance? The manual I received is a bit vague on that matter. There seem to be three distinct settings:

 

(1) INTERN

(2) INTERN + RE-CLK

(3) EXTERN + RE-CLK

 

While I can understand what (2) and (3) are accomplishing (they correspond to MC-3+ (without the USB) functionality) -- what is the difference between (1) and (2)?

[iago]

Thank you SwissBear and gldgate for responding, and sorry if I created more confusion by asking. I was comparing settings between MC-3+ and MC-3+USB, which have changed slightly. Both MC-3+ operate with or without reclocking, which seems to be selected via the MODE switch; only in MC-3+ only one option is lit at one time, in MC-3+USB either one or two options can be selected. I was wondering about the difference.

 

Clock reference source is still selectable via the REFERENCE setting. I believe you can tell if MC-3+USB is in re-clock mode by the STATUS LEDs: if the device is in re-clock mode, two of the status lock LEDs are lit (input PLL, output PLL?), otherwise one.

 

Here are my current settings for reference. Please note that I am running the devices with external clock reference.

 

MC-3+ settings

 

MC-3+USB settings

[iago]

Hi SwissBear,

 

the improvement is something I am still evaluating ;-)

 

With MC-3+ it was definitely there, with MC-3+USB I'm still struggling to pin-point differences between 'naked' USB-to-S/PDIF, re-clocked conversion and external reference. I think I will have to get used to the new device (some may call it burn-in) before I can make a more conclusive statement.

 

Which clock are you using as an external reference ? Did you notice any improvement compared to internal clock reclocking ?

 

 

The clock is a TEMEX LPFRS-01 salvaged from an old telco installation; I bought it second hand on ebay some years ago. The performance of this clock source is OK, but not up to modern standards. I had the chance to test Orbital Research POS some time ago, it was slightly better, but the improvement (for me, in my system) was not enough to justify the expenditure. For a new solution I would currently consider Rakon ROX3827T3.

[iago]

Interesting. How did you get your hands on the Orbital Research? Is it configured with 50R output? How is that terminated? What kind of power supply do you use? And if you don't mind, how much is the whole package?

 

The Orbital Research was configured for 50R termination, just as the Temex is. It was part of a package that I had the chance to evaluate in my system some while back. A 50R clock source is not compatible with the Mutec's input, this is why the Mutec MC-3+ had the option to remove internal termination and replace it with external one. I find no mention thereof in the MC-3+USB manual. The difference between proper termination and 50 into 75 Ohm was not great with Temex and MC-3+; but this seems to be very much source and destination dependent. I use a Hameg HM7042 to power various components that expect to be supplied by DC. It may not be audiophile, but it is incredibly fast and protected electronics from user errors in the past :-)

 

The whole package? The POS based solution (in a proper case with its own power supply) would have cost 1000 €, my current solution (looks more like a laboratory setup) was 100 $ for clock source, the power supply was already present.

 

If you build your own from available components (clock module, power supply, case, various connectors) you should calculate something between 1000 $ (excluding sales tax) and 1000 € (including sales tax).

[iago]

maybe is an answer but i would like to hear the engineer side: is a super external clock with 20 inches of wire is more stable than a 1ps internal clock ?

 

The 1ps value is the jitter equivalent for the oscillator chip. Through dividing the clock and processing audio signals this value will rise. I have seen estimations that the complete device has intrinsic jitter of around 50ps.

 

External frequency standards use 10 MHz frequency, which makes wave length approximately 20m (assuming c/c0 = 0.7). Half a meter of transmission line would not have a significant impact on the oscillator signal - if you take proper care of the quality of the connection, as *progear stated (cable impedance, connectors, termination).

 

While accuracy [1] and stability [2] play a role in usual clock applications, phase noise is probably more relevant for use of a clock source in audio, and here especially the phase noise distribution. The absolute height of the "noise floor" (which has the greatest influence on the one-dimensional jitter value) is of less importance than the area of least offset from the oscillator frequency (left margin of diagrams below). Differences in noise distribution might explain why external clock sources can bring an improvement over the internal one.

 

Actual phase noise diagram (source: Temex) and theoretical noise distribution (source: Analog Devices)

 

[1] Deviation of the sample clock's frequency from the nominal value, usually expressed as quotient of the clock frequency (df/f)

[2] Long term drift (ageing) of the clock's output signal, also expressed as df/f