If you’re going directly to line level inputs of a recording device as suggested chances are it’s coming from the microphone’s internal capsule pre-amp, some of the older microphones sought after for their character and warmth especially the tube versions have rather noisy electronics. Check input signal level. The input signal may be too low. If so, boost the incoming signal (if possible) or move your mic closer to the signal source. Obviously drum over-heads will need a lot less gain than an acoustic guitar.