MidSide Passive...

[abechap024]

Hi,
Had this Idea for a while, there must be something not technically correct with this design because I've never seen this around...but I made one a while back and remember it working...and the insertion gain drop wasn't too bad...But I don't remember I think i used a different set of resistors, I think I left it unbalanced on the output.... But I don't know, is there a way I could improve on the design? I'm planning on making a m/s encoders and crush n blend multichannel box to save some AUXs in my shop. If I could get the resistor design to work I could just as easily have makeup gain in the Mid/Side volume section after it. The design also takes for granted it is being fed with Differential balanced signal.

www.acsoundstudio.com/DIY/midsidepassive.gif
Thanks!
AC

and sorry about the scrawled drawing!

 

[Moses]

My guess is that you'll end up with a 'wide' mono, and a 'narrow' side as the signals crosstalk into each other... People use transformers for this for a reason...

 

[LeeYoo]

Excuse my dumb question, but what do you use it for.

I use m/s recording by using three channels of my mixer. Front mic into one channel, feeding L and R (mono/mid).
The side mic connected to TWO strips of the mixer. One normal, and one XLR reversed (home made lead, no resistors).
One of these channels goes to L, and the other one to R. Can also roll off the bass, correct gain, balance, tone this way of the S mic.
Monitor my DAW  X/Y scope for separation etc.

 

[abbey road d enfer]

Hi,
Had this Idea for a while, there must be something not technically correct with this design because I've never seen this around...but I made one a while back and remember it working...and the insertion gain drop wasn't too bad...But I don't remember I think i used a different set of resistors, I think I left it unbalanced on the output.... But I don't know, is there a way I could improve on the design? I'm planning on making a m/s encoders and crush n blend multichannel box to save some AUXs in my shop. If I could get the resistor design to work I could just as easily have makeup gain in the Mid/Side volume section after it. The design also takes for granted it is being fed with Differential balanced signal.

It works even with unbalanced sources, but the inputs must imperatively be balanced. Performance will be directly related to CMRR of the inputs. With a matrix of 10k resistors and an input impedance of 10k, the attenuation is 6.02 dB.
It doesn't work with unbalanced inputs, even when sources are balanced.

 

[abechap024]

Thanks Abbey!
So basically if I very closely match the resistors It will *work*. But I'll probably be better off using an opamp design. I'm going to throw a passive set together, just to test it. Thanks for letting me bounce my ideas off your guys-es minds.
And LEe Yoo I'm planning to use this as a 4 stereo channel M/S matrix box along with the crush and blend schematic SSL Tech posted. My main purpose will be with with compression, I can convert a signal to MId Side send it to compression. Any signal coming out of my DAW or mic pres. I can convert a signal in my DAW but I'd rather just have it right in front of me. And the purpose of the crush and blend will be so save me and AuX or two. I'm also going to add a circuit that adjusts the balance of the mid to side, the program FL studio has this build into every channel and is very useful.
AC