summing mixer pics and schem

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for the sake of anyone interested in building a summing mixer, here are some pics of an experimental "work in progress" that uses a combination of transformers and analog devices 2141 as inputs. it also has a 4-winding output Cinemag transformer that allows several outputs. it can use either 5534 or op604 for the summing amps. i prefer the 604. i am using an external Lambda +- 18 psu. this thing looks like a rats nest as i like to change things on a daily basis lately, but, it sounds awesome. one day i wll convert the whole thing to one circuit board. in the beginning it started as a 48 ch bal input mixer for monitoring 6 tascam da88's. you will see the board underneath with all the mogami coming off of it for connection to the inputs and to the summing boards. not looking to win any beauty contests, but maybe it will make some sense to someone trying to build a similar version of the dangerous 2 bus(which so far i haven't seen an actula unit or schematic for it). any schematic improvements welcome.

my schematic here:

http://carterdemo.com/sumschem3.jpg

pics here

http://carterdemo.com/boxback.jpg

http://carterdemo.com/topview.jpg

http://carterdemo.com/sumboards.jpg

http://carterdemo.com/transformers.jpg

http://carterdemo.com/trans2.jpg
 
I found that having an LM833 at the summing junction was better than the 2142.
This also gave a buffered unbal output as well as the 2142 bal output.

If you do use a 2142 and multiple windings output trafo, do be careful that the load on the 2142 doesn't drop too low cos they do get week into double teminated loads of less than 300 ohm ... even 300 is getting low.

I do have a couple ALL PCB mounted 12 and 16 mixers if any one wants to see a picture I guess I could get the camera out sometime.
 
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