I currently have a DIY M-S decoder, which is very noisy and the stereo image is wrong. The mid is much lower than it should and the sides are overbearing. Basically, it is impossible for me to monitor properly.

I don't want to decode before going into the recorder, this is just to monitor accurately. Do you know of a good option for me?


  • How's your DIY setup work? May 9, 2011 at 21:19
  • @ragamesound It's a bit of electronics that do the decoding. I plug in the stereo out from my headphones into the box and then my headphones into the box. It's horrible though. In any case I now have myself the Sound Devices, which have onboard decoding. May 10, 2011 at 8:00
  • Modern mobile digital recorders have M/S decoding built in. If one is using such a recorder anyway, an extra decoder might not be necessary. Dec 16, 2017 at 22:03

8 Answers 8


I know AEA used to make one, but Wes pretty much dropped all projects other than strictly Ribbon mics, but you can probably find one used somewhere for fairly not expensive...

Millennia and Dangerous make expensive ones, but obviously those won't work...

Most field mixers have m/s decoding built in. I know the Wendt X5, Sound Devices 302, and PSC ProMix 6 all have it. There may be a less expensive mixer that has it built in, you might be able to find one, or something used (on Coffey Sound or Trew Audio maybe?)

I haven't seen a stand alone decoder under a grand though.

Alternatively, you could use a y-split XLR cable to go into 2 channels (on your side channel) and use 3 channels and decode manually. You could either phase reverse the splitter manually or phase reverse on your inputs if your mixer supports it.

Good luck!

  • I'm actually considering getting the Sound Devices 302, it seems like a lovely machine. No ways I'll pay a grand for a standalone decoder :-) Thanks for the advice. Mar 7, 2010 at 14:36

There was a diagram at Jensen-Transformers of a "Passive Stereo Matrix for M-S Mic Technique" that might work.

I decided to test it, but then I bought a Wendt X3 which, although it is not a Mid-Side decoder, has 3 mic inputs, so I use an adapter cable to connect Side (figure of eight) mic to inputs 2 and 3 with inverted phase, if necessary.

Wendt x3
(source: wendtinc.net)


I second the "decode manually" suggestion. It's not complicated, and you'll have full control over the image.

If you don't know how to do that, there's a little article about it here: http://www.wikirecording.org/Mid-Side_Microphone_Technique

  • So you mean decoding before going into the recorder? I would rather decode only for monitoring purposes, and save the proper decoding for the studio and monitors. Thanks for the link you sent! Mar 8, 2010 at 19:37

I love the sound of the AEA decoders, but I'm often just doing it in software these days.

  • Yeah, the decoding I want to do in software. It's for monitoring purposes that I'm looking for one. I think I might get rid of my FR-2 (or keep it as a second recorder) and get a 7 series Sound Devices, that will solve my problem (and others). Mar 13, 2010 at 21:37
  • you also might want to search ebay for a sounddevices mp-2 pre-amp. It is the same as the mix-pre but it came with a decoder. It has been discontinued, but I bet you can find one used.
    – sepulchra
    Mar 14, 2010 at 21:26

Peter Engh makes the SonicOrbit a dedicated MS decoder.

  • peterengh.com/sonicorbit.php here's a link to that - but it looks to me like it's not for monitoring M/S, and there's no price listed. May 9, 2011 at 21:21
  • I just called Peter Engh up, here's what he says: Cost = $388 + shipping. Line level device - won't pass phantom. Designed to be between the mixer and the recorder. Cannot monitor directly from the device. "Most people use it" as part of the recording chain, not as a monitoring tool, but it could be used as a monitoring tool if you flipped the chain around. I.E. take a feed from your recorder, into this, into a mixer, and monitor from the mixer. Probably not the best solution for monitoring. May 9, 2011 at 21:29

I'm building a Passive Mid-Side encoder that might do the trick for you. It has multiple ins and outs, you can monitor each channel with dedicated direct outs, uses quality Jensen transformers, and for now it comes in an attractive box hand made from reclaimed redwood. I'm going to sell a couple of these soon for something less than a grand ($US).

There's more info at http://www.glenglenn.com

Glen Glenn Audio.


The Shure FP-33 field mixer has mid-side monitor decoding built in. You might be able to pick used one pretty reasonably. Sound quality is good.


What is your definition of "good but cheap?" That can be highly personal...

If you aren't averse to rack units, IGS Bison has a 500-series M/S decoder and wet/dry mixer with stereo inserts, so you can also use it for M/S processing or mixing: https://www.igsaudio.com/download,919,IGS+BISON+500+manual+v1.pdf

My Tascam DR-40 has built-in M/S decoding and encoding that allows you to monitor a M/S recording. It is "good" in that it does the M/S encoding and decoding correctly (which is not difficult) and it is "cheap" in that it came with the recorder and the recorder did not cost much but also does a good job of field recording from 1 (ext), stereo (internal mics or external mics), 3 channel (stereo mics plus one mono ext mic) or 4 channel audio.

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