mikep

building an M-S matrix, GML style
« on: February 15, 2007, 09:33:14 AM »
I use an 8200 eq in my stereo CD mastering rig.  the studio has 2 more 8200's that I can use.  I am not intrested in surround, I believe that is a dead end, waste of time.  I am thinking about modding one of the other 8200's for full-time M-S operation.   this is a little bold so I wanted some opinions first.

The reasoning for putting a mod in the EQ instead of making a stand-alone encode-decode box:  I can tap into the EQ's power.  I can insert the (unbalanced) matrix between the EQ circuitry and the existing balanced i/o circuits.  I would use an OR gate off the left/right bypass switches so that if both are out, the whole box is bypassed, if either is in then the matrix is active as well as that channel's EQ.  

I have several MS matrix designs but havent decided on one yet.  Id love to use GML opamps, but that would be a little pricey.  I could do it with only 4 opamps total so maybe it is worth it?  any thoughts?

mike p


pucho812

building an M-S matrix, GML style
« Reply #1 on: February 15, 2007, 09:37:31 AM »
I would make it external...
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

gyraf

building an M-S matrix, GML style
« Reply #2 on: February 15, 2007, 09:55:02 AM »
Quote
I would make it external...


And passive, transformers-only. That way you don't need the psu..

Jakob E.
..note to self: don't let Harman run your company..

mikep

building an M-S matrix, GML style
« Reply #3 on: February 15, 2007, 10:21:39 AM »
Quote from: "gyraf"
Quote
I would make it external...


And passive, transformers-only. That way you don't need the psu..

Jakob E.


these thoughts crossed my mind.  I could even build it as an external companion to the EQ and still tap into the power, as the 8200 has a daisy chain power connector on the back.  also in the room I have a big pre-regulated supply at +/- 30V I can juice out from.  the thing is, unless I get an analog de-sser, there will never be anything inside the matrix other than an EQ, so I thought, why not dedicate an 8200 for this purpose, since it would be patched there permanantly anyway?  by putting it inside I avoid introducing 2 extra sets of balancing/unbalancing amps.  I think. maybe this IS moronic.

I am concerned about the transparency of an all transformer design.  I usually already have "too many" transformers in the path, via either a neve compressor, tubetech EQs, or a McIntosh poweramp-as-a-lineamp. Whe I was thinking external I was considering a design that uses a transformer to derive the difference signal and a discrete virtual earth amp for the sum.  or a THAT line reciever for the difference amp.

mike

pucho812

building an M-S matrix, GML style
« Reply #4 on: February 15, 2007, 10:58:33 AM »
you can do passive and transformers and make it non coloured trafos. Jensen  transformers has a great schemo in the application schematics for the very thing. going with what I said earlier, by doing an external box you are more flexible and also you don't have to hack up an 8200 to do it...
passive M-S box with trafos is the way to go... :thumb:

Quote from: mikep
Quote from: "gyraf"
Quote
I would make it external...

 
the thing is, unless I get an analog de-sser, there will never be anything inside the matrix other than an EQ, so I thought, why not dedicate an 8200 for this purpose, since it would be patched there permanantly anyway?  by putting it inside I avoid introducing 2 extra sets of balancing/unbalancing amps.  I think. maybe this IS moronic.
 
mike

Not Moronic just a the hard way of doing things IMO.
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

chrissugar

Re: building an M-S matrix, GML style
« Reply #5 on: February 16, 2007, 12:22:04 PM »
Quote from: "mikep"
The reasoning for putting a mod in the EQ instead of making a stand-alone encode-decode box: ............ I can insert the (unbalanced) matrix between the EQ circuitry and the existing balanced i/o circuits.


Quote from: "mikep"
... by putting it inside I avoid introducing 2 extra sets of balancing/unbalancing amps.  I think.


You will not avoid the two extra sets of balancing/unbalancing circuits because the GML has unbalanced out on XLR (not even impedance balanced) the input has a discrete balanced receiver with DC servo so you can't avoid it anyway.

chrissugar
Christian Mike Sugar
        CMS-LAB


 

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