Low sound in Snapz

[göran]

I have a iMac DV SE 400 Mhz with internal mic. When I try to record
speech in system 10.2.3 I get very low sound level despite max sound
input. I am trying with Quickvoice and SnapzPro but get the same poor
result. What can I do? Buy a mic? Would it help? I borrowed two external
microphones and connected to the mic input but still got very low sound 
level.
Do I need an amplifier for microphones? Would iMic help?
Grateful for all suggestions.