That's not how it's supposed to work, you know. By using AC-coupled sources, you're actually going to have trig/gate signals (of a sort) that aren't exactly in time with everything else. There'll always be a little lag. And as you've noticed, not every module will respond to this method.
Why NOT get a DC-coupled interface? You don't have to get something like an ES-8...you can get on eBay or Reverb and rustle up a secondhand MOTU 828 (I use a mkii FW version for synth control, linked via Firewire 400 to my DAW machine) for, at worst, about $150. Plays nicely with CV Tools in Ableton. Plus, it gives me eight return lines, which is great if I want to use a hardware synth to generate modulation signals for something in software. And I should note, you CANNOT do that without a DC-coupled interface!