More on Crosspoints.

[Tony Clark]

>   This isnt very clear, its difficult to put into words..
> 
> 1>   ooooxooo
> 2>   oxooxooo
> 3>   oxooooxo
> 4>   ooooxooo
>  
>   Ok in the above example imagine that 1,2,3,4 are CVs going INTO the matrix
> and that the
> X's represent an ON point.

   Can crosspoints wire two or more inputs to the same output?  I 
wouldn't think that very wise as they don't have a summation amp on each 
of the output lines!
   I have been thinking about this sort of situation for a few weeks 
myself and I think what you really want to do is use an analog 
multiplexer and then run each of your input lines with a summation amp 
that has enough inputs as your matrix array.
   So, if you have a 16x16 grid, you would need two 1-to-8 analog 
multiplexers per output, and on each input a summation amp with 16 lines 
in (one tied to a unique multiplexer line on each output).
   And in that setup, you'll want the lowest ON resistance as you can get 
(although most likely anything under 50 ohms will be adequate).
   Unfortunately this won't help in the chip count area, lots of chips 
(at least 36 for a 16x16 array (32 multiplexers and 4 quad op-amps)), 
BUT the added benefit of using individual multiplexers is that your 
crosstalk can be fully controlled, unlike what you will most likely get 
in a switch array.
   Hope I've helped some!

   Tony

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I can't drive (my Moog) 55!         |     The E-Music DIY Archive
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Tony Clark -- clark at andrews.edu     | aupe.phys.andrews.edu/diy_archive
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