redirecting 3.5mm jack input

[ren_zokuken01]

since i still don't have my PC back (thought i am very, very very, very anxiously looking forward to getting it back ASAP), i play my MP3 music from my cheap cellphone.

i also happen to have this alarm radio that's got a big speaker. it's got no audio input jack, though. now basically, i want to add a 3.5mm audio input to it.

seems easy enough, but my question is, say if i have the radio on, so the pre-amp is taking the audio signals from the radio component. how do i make the pre-amp take the signal from the said 3.5mm jack when i INSTANTLY plug in my phone?

i'm getting my jack from here:
http://www.digikey.com/product-search/en/connectors-interconnects/barrel-audio-connectors/1443095?k=3.5mm%20jack

if i have stereo, do i choose a jack with an internal switch of DPST? coz i remember my high school electronics teacher showing me some sort of jack with a contact leaf that lifts when he plugs in a 3.5mm connector; back when he built an amplifier once.

[Muhammad Abu Bakar]

You have a clever idea. I don't think it would be a pretty work. You need to trace the circuit where audio amplifier takes input. Then tap these wires out. No gaurantee that it will not damage the rf output.