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Sonosax M2D2 buzz on Schoeps mikes

Fred Salles

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I am having trouble with the M2D2 I am working with this month.

It started giving me a weird high med buzz whenever I plug two CMC6 Schoeps mikes (+MK4 or MK41 same behaviour). When unplugging one of them buzz gone, either of them. When plugging the mikes directly in 688 no buzz at all. When plugging a MKH50 + a Schoeps the buzz appears but goes away pretty fast.

I was outdoor in pretty cold and humid environment when it started but it remained when back indoor. We did extensive testing (M2D2 stand alone on internal batteries) and ruled out anything but the phantom power system from the M2D2. The CMC6 requires slightly more power than MKH50, even though still very low (4mA against 2mA) could that be one explanation? We tried 4 different CMC6, the younger ones retained the buzz but it goes after some minutes, with the older ones  the buzz remains much longer (more than 5 minutes+). Again no pb with all of them plugged in the 688. I also did a thorough cleaning of the connectors.

It seems to me that one of the 48v blocking capacitors could be faulty but not sure, especially it does not really explain why it works fine with just one mike plugged in.

Any thought welcome


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it is the SN00056

I have noticed that the internal battery needs to be inside even when powering from the hirose DC in socket: Strangely if you take it out it does start and work with one mike but as soon as you plug 2 the machine goes off...

Definitely will look at getting a new battery.


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On 10/17/2021 at 7:58 PM, Patrick Tresch said:

Yes early Sr. nr (until 100 I think) didn't have an unballanced protection (circuit protection). When switching on the 48v power on an unballanced connection It would do an overload of the circuit. (I believe).



Not sure I follow you. Are you talking about the analogue unbalanced outputs ? I do not use these.

I use AES out and always make sure I set the recorder's input on the correct setting before plugging. But anyway the problem appears even when tested stand alone (earphones output only).

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I do speak about the analog input. If you used an unbalanced input source but you kept accidentally the 48v power on, it would have made an overload of the circuit. Frequently  pluggin and unplugging a mic with 48v without switching the power of the machine to off would also produce such an overload of the circuit on older machines with early serial number. Sonosax fixed mine for free.

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