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Review and Teardown of Douk audio MC103 PRO switch

LTig

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This is a review of the MC103 Pro XLR switch sold by Douk Audio. There are two versions with the same model name:
  • 3-to-1: 3 inputs (XLR female) and 1 output (XLR male)
  • 1-to-3: 1 input (XLR female) and 3 outputs (XLR male)
The price is around §/€ 60.- for each of them. I have them both, but the review covers the 3-to-1 version.

Here is the view of the front - please note that I took this photo with the lid unscrewed, that's why it is not sitting correctly on the right hand side.

MC103 Pro front.jpg


View of the back (also taken with lid unscrewed):
MC103 Pro back.jpg


The switch looks a bit cheap, neither fancy nor over the top. Front and back are plastics, bottom and top are metal (aluminium). I would have preferred a full metal housing for better shielding. The switch works precise but does not feel expensive.

Teardown
To open the housing remove 4 screws and lift off the lid:

MC103 Pro top2.jpg


Measurements

I used my RME ADI-2 PRO fs with +24 dBu reference level to get the highest possible Signal/Noise ratio. The cables were 40 cm long and made by me using Neutrik connectors and Klotz microphone cable. For comparison the following plots always show the loopback performance of the RME for comparison.

THD
I used a 1 kHz signal with +21 dBu level because the THD of the RME is lower at -3 dBFS than at 0 dBFS. I set REW to average 16 spectra of 32 kHz FFT size to dig deep into the noise.

ONE Little Bear MC103 Pro 3in 1out XLR THD +21 dBu right channel.png


As one can see there is no difference between the switch and the loopback. We can safely assume that any distortion or hum added by the switch (if any) is below that of the RME. We need an AP to dig deeper.

Crossfeed
I measured with several sinus signals between 20 Hz and 20 kHz at 0 dBFS output. We see 5 curves in 3 groups:
  • green/orange: crossfeed of the switch, from left to right channel and from right to left channel
  • pink: crossfeed of the switch, from left channel input X to left channel input Y
  • red/blue: crossfeed of the loopback, from left to right channel and from right to left channel
ONE Little Bear MC103 Pro 3in 1out XLR crossfeed vs frequency.png


Results:
  • Above 1 kHz the crossfeed between inputs is 12 dB higher than the interchannel crossfeed of the RME.
  • Above the interchannel crossfeed between left and right channel of one input is about 24 dB higher than the RME.
  • Below 1 kHz the crossfeed results suffer from the inherent noise of the RME although on a very lowe level. We can safely assume that the real crossfeed curves continue to decrease with decreasing frequency.

EDIT:
As @MC_RME has stated in posting 7 the reason for the higher crossfeed above a few hundred Hz is capaciticve coupling. He recommended to redo the test using the balanced phone output due to its much lower output impedance (0.1 Ohm vs. 200 Ohm). Here is the result:

ONE Little Bear MC103 Pro 3in 1out XLR crossfeed vs frequency PH BAL.png


Yep, we are more than 20 dB better at 20 kHz. Looking sharp one sees that the crossfeed of the switch is identical to the RME loopback, so what we see is the limit of my measurement rig. Well done, Douk Audio.

Conclusion
I have been asked whether this switch is an "audiophile" device and whether it could be used between a highend DAC and a highend power amp. Regarding the results I simply say yes. Both distortion and noise added by the switch are below audibility level in all home environments I can think of. Whether an audiophile wants to use such a cheap looking device in his highend system is another question I'm not going to answer.;)
 
Last edited:

GokieKS

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I have one of these between my DAC (RME ADI-2 DAC FS) and power amp (March Audio P252), and it works perfectly fine. My only issues with it is that the knob doesn't line up perfectly on the center Y marking (but I only use two inputs so I just use X and Z instead), and that it's so light that sometimes the thing will move when I switch inputs if I don't also use a hand to press down on the casing.
 
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LTig

LTig

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Oh, I just bought one to test because I plan to use it to switch between powered monitors for testing. It just came today! :)
Too late ... :p
Well, let's see what your AP finds below the noise floor of my RME.
 

jjk

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This would be really helpful to me, reference my issues with the Freya!
 

KMN

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Does anybody know if pin 1 is switched? or is it just pin 2 and 3 switching?
 

MC_RME

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I excpect the crosstalk to be capacitive coupling on the switch PCB.

What you could try is using the phones outputs in balanced mode with a TRS to XLR M cable. Output impedance is then down to 0.1 Ohm (instead of 200 Ohm). That would remove the influence of capacitive coupling. It would also explain why Amir had measured lower crosstalk (APx has 40 Ohm output impedance).
 
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LTig

LTig

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Does anybody know if pin 1 is switched? or is it just pin 2 and 3 switching?
Just measured with my ohmmeter:
  • pin1 and the shield are always connected
  • pin 2 and 3 are switched
 
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LTig

LTig

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I excpect the crosstalk to be capacitive coupling on the switch PCB.

What you could try is using the phones outputs in balanced mode with a TRS to XLR M cable. Output impedance is then down to 0.1 Ohm (instead of 200 Ohm). That would remove the influence of capacitive coupling. It would also explain why Amir had measured lower crosstalk (APx has 40 Ohm output impedance).
Done, and of course you are right:

index.php


At 20 kHz we are more than 20 dB better. I've added the plot to the review above.

OTOH I think that the first measurement using the normal outputs with 200 Ohm output impedance may be closer to real world applications. We know now that sources with higher output impedance suffer higher crossfeed.
 

MC_RME

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Yes, we have to draw the right conclusions. Using 0 Ohms showing a near perfect result does not mean the switch works and we ´(I mean you and Amir) measured it the wrong way. Indeed it should be perfect with 200 Ohm source impedance. So the layout or internal design of the switch could be better (I doubt the front switch itself is doing this...maybe only partly).

On the other hand we are talking about numbers that are far away from any real-world problem, so we learned something and can now forget this 'issue' ;)
 
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