hi,no, you cannot plug your headphones into the minilab - it is a master keyboard, not a sound module, it cannot produce any sounds.an iOS device is a good option for producing sounds. your iphone 3G, though, will most likely not work as it is too outdated in terms of processing speed and resulting software capabilities. sorry!i use the minilab with an iphone 5S and an ipad mini retina. both work fine using the apple lightning USB adapter. no additional power necessary, minilab is powered by the iOS devices - very handy when on the go. controlling various synth parameters in realtime via knobs (MIDI CC) works fine, too.good luck