My name is Tri, from San Jose, Califronia U.S.A, i'm a student at DeAnza College, Cupertino, majoring in BioTech had no background of electrical or sound.
I started Googling for a mini Microphone booster for sound recording. I had a Motorola Razr v3m phone which has a Audio-Recording feature only allow to record up to 3MINS, however, with some computer knowlege i was able to modified the phone system files to have unlimited voice recording durations.
As you may already know, built-in microphone on most cellphone aren't that high quality, on top of that Audio only being recorded at 10kbs, recording bitRate is fixed no way of changing it. To my understanding, compare 10kbs audio file to most Mp3 songs are between 128-320kbs is no match.
The reason I'm wiriting is, i'm using the phone as voice recorder to record my Biology lecture class to listen to it at later time. So far the recording works just fine but what bother me is, when the instructor giving the lecture he does not stand in one place, he walks back and ford in the lecture hall.
I had my phone sit on his desk but he could be on the other side of the room, so it kinda hard for the phone to pickup the any frequence. I'm thinking if there is a external microphone booster to boost the microphone so it could pick up his voice even though he is on the other side of the room.
I found a couple for $50-150 but i guess i don't want to spend that much, according to your article homebuilt preamp for 5bucks could do the job. I just want to check if this microphone preamp could help boost the voice from far away. or its just for amplifying the voice for better vocal.
If its not, do you have any suggestions on how to build one that could get the microphone to be sensitive for my purpose of use. I remember watching on the dicovery channel that the scientist could able to record foot steps of ant walking on the platform, aren't they using the same techneque by tune microphone to high sensitive that helps them get the result.