M/S encoder/decoder

Hi,

I'm using a lot os MS recording techniques and decoding the MS signal seems pretty easy to achieve using three channels on my console. I understand how it's working and have pretty good results.

some times ago I used a box wich decoded the signal coming from the mic and put it into stereo with a wide control,. A very classic box. It was cool as it saved me on channel on my desk. So I planned to build one of this box, I founded some schematics and wanted to start

But someday I came across those wonderfull machine which can also encode a stereo signal into MS signal wich is really usefull especially in masteriing configuration. So I though it was a good idea to combine the two function in one box as a MS encoder/decoder tool.

But my poblem is I absolutly can't understand how the stereo signal is encoded into an MS signal.. And I can't find any schematics whih can explain how to build such a machine or which can explain hox to do so using my console'schannel...

Do you have any idea ???

Any schematics would be really helpfull

Thanks a lot

:thumb:

This may help you.....

http://www.uneeda-audio.com/ms-mat.htm

Cheers
Urs

..or try a forum search here. has been discussed several times..

e.g.:
http://www.groupdiy.com/index.php?topic=5002

Jakob E.

I did a orum search but couldn't find anything usefull

hint: look for e.g. "matrix", as the search engine insists on at least three letters in a search..

Jakob E.

The matrix that turns an L-R (or "XY") signal into an MS signal is exactly the same matrix that turns an MS signal into an XY signal. It can be mathematically proven that these two operations are one and the same. The matrix, as I'm sure you realize since you've been doing it on 3 console channels, is sum-and-difference. The algebra, as you'll see, is dead simple:

M=(L+R)
S=(L-R)
(L+R)+(L-R)=(2)L
(L+R)-(L-R)=(2)R

For a simple passive transformer-based matrix, see Jensen's schematic:
http://www.jensen-transformers.com/as/as055.pdf
You don't have to use their transformers to make this work. Any split-primary or split-secondary transformers suitable for line-in line-out use will be fine.

I suggest that MS microphone arrays be recorded in MS, and decoded at mixdown (or mastering/post-production, if they're the only microphones used in the recording). Of course you will still want to use the matrix during recording for monitoring purposes.

If you're recording to a DAW, it makes much, much more sense to matrix it in the computer since it can be done absolutely perfectly (as much as I like transformers, this particular task is much better suited to the digital domain).

Of course all three approaches (Console, transformer, or digital domain) can be modified to include L/R balance and/or stereo width by the inclusion of attenutation either before or after the matrix.