Yamaha S80 A/D Input question

[pete psingpy]

I'm trying to connect the output of 2 synths into the mono A/D input on my Yamaha S80. I currently have a korg DW8000 plugged into the A/D input, and it works great (allows the korg to use the S80's effects).

 

I've added a roland JX-3P to my setup, and I'd like to be able to run both the korg and roland through the A/D input.

 

I've tried a couple of things:

 

1. patch the DW8000 and JX-3P into a RadioShack mic mixer, and then the mixer output to the A/D input. But no matter what I did with different cables, connectors, and input level settings, I could not get a clean signal. I'm picking up a lot of noise.

 

2. Patched both the DW8000 and JX3P to a mackie 1202VLZpro (mono inputs), then ran a cable from the Aux Send 1 on the mackie to the S80 A/D Input. This worked a bit better, but still had the noise problem.

 

I'm not sure what else to try, but before I give up, I thought I'd ask if anyone out there has done something like this or has a suggestion.

Thanks