OK, thanks. Had a good look around today and while I am still hoping to find a splitter with a stereo plug, I am impressed with the Tascam DR-60D. While it is something else to carry it also gives me backups etc which is very useful.
I think you'll be much happier going this route. That looks like a nice recorder and it can connect to the bottom of your DSLR. The Tascam stuff also sounds a lot better (to me) than the Zoom stuff as far as recorders go. I've found Zoom preamps to always sound harsh and thin, Tascam is very good mid-level equipment and they have a solid reputation for making recorders that goes back quite a while. That recorder will also open up the possibilities for using all kinds of different microphones.
If you are shooting interviews, I do advise you to get a slate for syncing audio with the visual of the slate sticks closing. You'll find that if you sync to the sound spike the camera records and the sound spike the audio recorder records, that the camera will be off by a couple of frames. It's not an external audio recorder problem, the audio recording of the camera itself is at fault (this is the case with all DSLRs, and indeed most video cameras) -- the on-camera sound is actually out of sync with the camera picture by about 2 (sometimes 3) frames. It's not always terribly noticeable, but it's worth knowing. Anyways, you can test this with a slate and see for yourself
Thanks, and yes I have noticed the sync issues at other times. I always wondered what caused that. But a good idea with the slate. :-)
The Tascam DR-60D does seem to address a couple of issues for me. An important one is that it will keep weight off the 1D X mic jack port - two xlr cables in a splitter hanging from there was always going to be a concern. Plus the other is backups. If you set the Tascam to 4-channel (learning from the YT tutorials already) you get a reduced volume image of your recording on the unit itself plus you can plug the thing into the camera mic jack and the camera will record too. So I should not have any excuses for bad audio in future.