Two-input Ruby as a practice amp?

[H5N1]

I want to plug a guitar and an ipod into a headphone Ruby.  I tried simply connecting the 1/4 guitar jack and 1/8 Ruby jack in series, but it doesn't work. The guitar and ipod work singly, but when plugged in together, the iPod signal gets shorted out.
Any and all suggestions appreciated.
-h

[PRR]

[H5N1]

Brilliant!
I'm going to put it together right now.