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[zakco]

Hi,

Is there any inherent problem with using a short (10') Y-cable to split a mic signal into two preamp channels for M/S recording?

I know it's OK with +4 signals, but how do mic levels fare in this situation?

Thanks,

-Zak

[Barish]

Y cables cause a 3dB drop on the signal level at the branches compared to the output level, so I don't think that there are any other side effects apart from that. That's something I have done a lot via patchbay and never encountered any other issues. or if there are any, I haven't noticed them.

[hollywood_steve]

The usual response that I have seen to this question is that line level signals can take a "Y" split without problem, but that mic level signals are more susceptible to potential impedance and noise problems and that a suitable splitter should be used.

FWIW, I just purchased my first mic splitter, the Palmer Audio PMS-02.  Its a very sturdy little box (2 channel) and I've been unable to detect any impact on the audio with/without the unit in the signal path.

[Brian Roth]

It should depend upon the input impedances of the preamps.  If the input Z's are considerably higher than the output Z of the mic, paralleling preamps shouldn't cause any noticeable differences, although that may depend upon just how "sensitive" the mic is to load Z.

Bri

[John Klett]

You don't want to do this for anything critical.  Anything that changes the loading that a mic sees will to some extent change the sound...  maybe not by much but by a little.  The amount of loss will vary from a little to quite a lot.

[bobkatz]

Barish wrote on Thu, 30 September 2004 17:49

Y cables cause a 3dB drop on the signal level at the branches compared to the output level, so I don't think that there are any other side effects apart from that. That's something I have done a lot via patchbay and never encountered any other issues. or if there are any, I haven't noticed them.

3 dB drop is not true.  Assuming a 150 ohm microphone and a 2K ohm input impedance for each input, then the loading with 2 in parallel is 1K. This is still effectively bridging. 0.6 dB more loss than with no Y cord and one channel. Into 1 K ohms I get 1.2 dB loss compared to open circuit. Into 2 K ohms I get .63 dB loss.

Remember: Turn the phantom on only one of the two channels.

[zakco]

john klett wrote on Fri, 01 October 2004 08:21

You don't want to do this for anything critical.  Anything that changes the loading that a mic sees will to some extent change the sound...  maybe not by much but by a little.  The amount of loss will vary from a little to quite a lot.

Ok. That does make sense.
The reason I was looking to use a Y cable, is for remote recording where I would like to monitor the M/S signal, but I do not have phase reverse on my little monitor desk. I can always hear it decoded on playback by reversing polarity in the software, but it looks like I'll need to make a couple of reverse-wired cables to handle the live monitoring. Or possibly buy a splitter box.

Thanks again,

-Zak

[Barish]

bobkatz wrote on Sat, 02 October 2004 00:02

3 dB drop is not true.  Assuming a 150 ohm microphone and a 2K ohm input impedance for each input, then the loading with 2 in parallel is 1K. This is still effectively bridging. 0.6 dB more loss than with no Y cord and one channel. Into 1 K ohms I get 1.2 dB loss compared to open circuit. Into 2 K ohms I get .63 dB loss.

Thanks Bob, that was an experimental value that I had reached at some point, I had never scientifically calculated it. I stand corrected.

Your "Mastering Audio" is one great book by the way, my bedtime reading for sometime. Thanks for that one too.

Regards,

Mahcem