DIY Passive summing mixer build

[dj_subjective]

Hi there guys, ive been all over the net and cant find what im looking for, i want to build an 8 channel passive summing mixer with no bells and whistles, just 8 ins and stereo out.

Heres where the fun begins, i have just got a focusrite saffire pro 24, whish has 2 pre's+ 2 balanced ins, 6 balanced outs and a stereo headphone out. now the 6 balanced outs going into the summing box in easy, but for channel 7 & 8 i want to use the stereo headphone out, which im shure isnt balanced.

Now my concept is to send 4 stereo groups to the box, using the 6 outs (3 stereo groups)and the headphone jack (stereo group 4) to be summed, but i dont want to slice up cables or mix balanced and unbalanced signals if its going to add noise or just end up being a mush mix.

I have found many designs on the net, but none that mix balanced & unbalanced signals in an 8 channel summing mixer.

Any advice,schematics or otherwise would be much appreciated. 

 

[signalflow]

Here is a kit you can buy that has everything that you'll need but If you do a search here on the site you will find a number of discussions on the topic.

http://www.diyrecordingequipment.com/store/product-category/endless-summer-analog-summing-kit/

-Casey

 

[dj_subjective]

i have seen this one, i have all the parts to make one, and ive been to this site and many other forums to try and find info on mixing balanced and unbalanced signals passively, but no one seems to have the expertise to give me info.

All the designs ive found are 'neve summing' clones, so they use either balanced or unbalanced ins, not a combo of the 2.

All i want to know is if its possible to mix the 2, and possibly an equation to get the resisters or a schematic or pics of an example.

 

[dj_subjective]

so much for DIY. order a kitset??????  im obviously on the wrong forum.

 

[signalflow]

Seems like Samuel answered a similar question 7 years ago.

http://www.groupdiy.com/index.php?topic=12016.0 took 2 min to find.

You could use a balanced summer and tie the "cold" input to ground for the unbalanced sources. If you use stereo jacks for the inputs and mono jacks for the cables (for the unbalanced sources only, of course), this is done automatically.

There is a slight degradation in "balance" when doing this, but probably not enough to matter.

A solution without this degradation is far more complex and needs transformers and/or active electronics for every input.

Samuel

Here is Fred Forsell's summing designs

http://forsselltech.com/media/attachments/8chsum_2.pdf

Just make some bal-unbal cables for the first 6 outputs and use un-bal cables for the HP out then make an un-balanced summing unit.  Sometimes the simplest answer is the right one and requires thinking "outside the box".

so much for DIY. order a kitset??????  im obviously on the wrong forum.

obviously.......there are 3 different kinds of diy.  The kind you design from the ground up, the kind you find in a kit and the kind you get an attitude with because someone didn't spoon feed the answer to you.

-Casey