ok. i bought a preamp today from jaycar i have wired it all up but it's not working. when i use a 12vdc power supply it hums like crazy and if you tap the mic really hard you can hear the thump. i am using shielded cable. i thought the power supply might be causing interference so i then used a 9v battery and then there was no hum but if i hit the mic extremely hard i could here a faint thump. whats wrong ? below are amp specs and diagram of what i have done.
kemo m040 preamp
Specifications:
Operating voltage: 9...24 VDC
Frequency response: 10 Hz ... 100 kHz
Input: 2 - 50 mV
Output: 200 mV 1 V
Dimensions: 30 x 25 x 15 mm