It wasn't really an SCA problem. Unfortunately, I don't know how the issue got resolved.
It was a really bad hum from the guitar amps (any of several tried) plugged into same outlet or not, w/ either the sca unit's D11 or my profire 2626's DI inputs or any other similar device. I changed a zillion things when troubleshooting and could not figure it out. No matter how I split the guitar signal, any connection from my guitar to the amp to 2/3 of the DIs I had handy had the same mad hum.
A few days went by, then I took apart the sca to change the jumpers as per your suggestions and put it back together and the hum was gone. Then I changed it so the only thing different from the earlier state was one ground lift jumper lifted. Then I could see if that was the solution. No hum on EITHER input. So I put it back the way it was.
No hum
Anyway, I hate it when an issue ends with no real information so the real answer to my question ends up being some other products.
A third solution I had handy through this that did NOT hum was an mxr bass di. It has an xlr di output that works swimmingly in all occassions I've tried. So I figured I'd still have to rely on that.
Today I got a Peterson Strobostomp and it has a nice DI that is only very slightly different from the mxr. They both sound very good and very similar to each other by my ear.
The Boss TU-2's tuner output into the SCA D11 into Profire 2626 mic preamps had quite a bit of hissy noise. NOT saying it's the D11 there are several other factors and long messy cable runs at this point.
Tim you should sell kits of some of the jensen reference designs, there's a huge need.
You could make them super flexible.
Put two transformers on a board w/ i/o. A pair of the 1:1 or a pair of the 1:12 or maybe one of each.
I built one of these recently and it's wonderful. I might try to somehow put it in the sca chassis.
http://www.muzique.com/lab/patent1.htm
http://www.jensen-transformers.com/datashts/dbe.pdf
http://www.jensentransformers.com/as/as013.pdf