DIY summing box?

[Slaytex]

Can anyone guide me in the right direction as how to build a passive summing box? Anyone have a schematic? I'm sure it's pretty basic, I would love to stick my head under the hood of a Folcrom.
Thanks.

[Matt Syson]

Hi
The essence is simply a bunch of resistors. Then you presumably want channels to be switchable so you need some switches. Then you want sockets so you can plug stuff in, then you want a box to make it look pretty, then you have a Folcrum.
To take it back to basics and you have a DAW using PT / Tascam wiring on a SubD25 all you actually need is a sub D connector, a bunch of resistors and an XLR plug or two to stick it into your mic amp input. This will work and it is cheap but you don't get the switches, extra sockets to do more exciting things, or a sexy box. The choice is yours!
Matt S

[Slaytex]

Cool thanks for the reply. I did some googling and found this:
http://www.forsselltech.com/8chsum_2.pdf
Easy as pie. I do not care for the switches as I will be sending everything out in stereo pairs.
Thanks.

[Matt Syson]

Hi
I am not wishing to say anything at all negative about the Folcrom unit or anyone else's for that matter. The simple design in the link has limitations in that disconnecting one or more inputs will affect the mix level but this is a fully workable solution. I had wondered about making one up on a cheap patchfield using the break contacts to short the inputs if unused thus keeping the levels constant. I don't want or need one personally so I haven't bothered.
Matt S

[ulysses]

That's one big difference between the circuit shown in that schematic and the one contained in the Folcrom. Switches are necessary if you ever want to vary the number of channels in use or their assignments to the left and/or right busses. Otherwise, leaving unused channels floating will affect the remaining channels in use. When you start adding switches, the parts cost and difficulty of assembly start to go way up. Without them, the usability of the circuit is severely limited. If one person is going to use it one way all the time for their own specific needs, this isn't a problem - just build it how you're going to use it. If your plans change though, you'll have to get out the soldering iron and rework it.

[Jason Poulin]

http://gearslutz.com/board/showthrea...t=roll+summing



it's a good one.



Jason

[Matt Syson]

If you can work out which end of an iron is hot you coule make up a couple of 'mixers' with say 7 into 1 mix and 1 direct out on 1 Dsub and the same for a second to give you a stereo mix and 2 direct outs on a 16 channel system. It's cheap enough to make a few variants which would be fine for the 'fixed' installation. Don't like it, just unplug and do something else!
Matt S