External Preamp

What’s all this about noisy pre-amps? And say, what is a pre-amp to begin with? It all goes back to how much electricity you can generate simply by talking. A microphone converts sound pressure waves (what you hear with your ears) to an electric signal. Talk into a microphone, and generate a small signal. Dynamic microphones require no additional electrical input to generate a signal, they do it with magnets. How much electricity can you generate simply by talking into a microphone and causing its small diaphragm to vibrate past a looped coil? Not very much. The signal is low. It needs to be amplified to reach the same kind of signal strength that most home and portable audio equipment uses.

The microphone’s weak signal is called “Mic level”

The standard signal strength for home and portable audio equipment is called “line level”—named (I presume) for the signal strength of the line between your cassette deck and your tuner. It’s the signal strength that goes from your iPod to your headphones. It’s the signal strength that goes from your computer to your desktop speakers or stereo.

How does the weak mic level signal get increased to line level? Mic levels get a boost from a pre-amp, or pre-amplifier. The microphone signal is amplifies before it gets recorded. Most portable recorders that take microphones have pre-amps included.

Quiet pre-amps and Noisy pre-amps. What are they, and which do I want? Pre-amps boost the signal from too low to just right.

I held the recorder up to my ear and I didn’t hear any noise. I didn’t hear the sea, either.

Noise occurs in the electrical signals. If the electronics are built in such a way, extra electrical current is leaked into the low signal, and exacerbated into hiss or hum or rumble when the signal is boosted to line level. In the great scheme of things, you get what you paid for. In order to offer a lower-cost piece of equipment, they cut costs.

To answer the question, which one do I want? You want quiet pre-amps. Quiet pre-amps give you all signal, and low (or no) noise.

Most recorders take microphones and have internal pre-amps.

Advantages: Good ones amplify without adding noise
Disadvantages: Poor ones add noise

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