I think the OP sorted it out...considering he asked the question 7 years ago.
Ummm...Nine???
But this is a pretty common question, and now that it's been bumped there probably will be some people clicking on it because they're in a similar situation. Unfortunately, there's a lot of conflicting information and no real resolution.
The real answer to this question is in reply #10. The document in that link has a very thorough discussion of all aspects of this question, and down at the bottom is a nifty quick reference chart and even wiring diagrams for about any type of "mismatched" connection we might need to make in the studio. Yes, it's pretty long, but not overly technical. Yes, it requires that you know something about your gear, and some of the information that you need isn't always on the spec sheet or even really available at all.
The fact is that with most modern gear (which is not directly cloned from vintage sources) will work fine with either a TS>TS or TRS>TRS cable. The first will short the source's R to ground (S) which might damage certain older gear, but I've never owned anything that cared. The second will just leave the R floating open, which could theoretically piss off some very uncommon types of circuits, but again shouldn't be an issue with most things.
The problem with TRS>TS cables is that there are several ways to wire them, and how they are connected matters. If you're buying cables, you will almost never actually know how they are wired until you get them in your hands and either inspect or test the connections. And if you build your own, you need to first decide which way is best for your application and then remember and/or somehow mark the cable so you can identify it later.
Rule of thumb: Plug it in with whatever is handy, and if it doesn't sound all fucked up (it probably won't) just go with it, but don't blame me if it starts to smoke.
It's about the same thing going the other way, too. Unbalanced source to balanced input has a different set of considerations, but it usually works fine either way.