I recently purchased a Casio CDP-230R digital piano, which so far has been working quite nicely, apart from one feature. It comes with a 1/4" microphone jack, with which you can sample a sound and then play it back using the piano keys. I have yet to get it to pick up any sound from either of two microphones: one that I got for my pre-school daughter (a very cheap Disney-branded plastic microphone with a flaky cord) and a nicer one that I ordered just this week (a Shure PG58 dynamic microphone), despite following the piano user manual's instructions to the letter.
What I've noticed is that if I plug a powered sound source (such as my cell phone playing an MP3) into the piano's microphone jack, the sound comes through as you would expect, its volume can be adjusted using the microphone jack's volume knob, and it can be sampled as per the user manual's instructions. However, the manual makes no mention of needing an amplified sound source, the diagram on page 18 shows a (presumably) unpowered microphone being plugged directly into the microphone jack, and the one relevant Google result I've found is from a user who says he "Just plugged it in and worked."
Does anyone have experience with the microphone input on this or a similar piano? Does it need a pre-amp, or am I just picking the wrong kinds of microphones, or might the jack be faulty?