Noise During Recording: Part 3

We’re continuing our series on noise during recording with preamp noise. This is noise created by the internal components of your recording system, specifically the op amps inside your microphone preamps.

This is most commonly an issue with budget audio interfaces or preamps-if you’re using a red Focusrite interface or something at a similar price point, this is probably an issue for you.

Diagnosing Preamp Noise

Plug in a mic, put on your headphones, and turn monitoring ON for a recording channel. You should now be hearing the sound of the mic picking up any ambient room noise in your ears.

Next, being very careful of your hearing, turn the volume up and down on your preamp, and listen to only the sound of the mic and preamp together picking up the empty room. Don’t play an instrument or anything.

If preamp noise is an issue, you’ll find a spot on the preamp volume dial where, if you go past it, the preamp starts to add a lot of noise into the signal. When you pull the volume back down, the noise will get softer. Often this point is around 2-3 o’clock on the input dial. Usually this type of noise sounds like a high frequency hiss at 5 kHz and above, but I’ve heard everything from clicks to buzzes to drones. It just depends on the exact preamp circuitry.

If you hit record with your preamp input knob set at this noisy level, you will be adding this unflattering preamp noise onto everything you record. When you turn the preamp volume down, the signal to noise ratio should improve and you’ll get a cleaner, yet softer, sound.

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Side note: all preamps, even the nice professional ones, add noise of some kind into your signal when you use them. The only difference here is that the noise of a cheaper preamp can be very loud, hissy, and unflattering. In contrast, many of the most coveted pro audio preamps add transparent or flattering noise that can make a source sound “warmer” or more appealing.

Solutions for managing audio preamp noise

1. Move your microphone closer to the source, then turn down the preamp.

2. If the signal is now clean, but too soft, try adding a software plugin to boost the gain further inside your DAW. Digital gain in a modern DAW is often very clean, so this may let you add some level without adding preamp noise.

3. Try using an in-line preamp (something like a Cloudlifter or Fethead). This is a small $100 gadget that adds a fixed amount of level between the mic and the preamp. This lets you drive your preamp less hard, which will add less noise, while still getting a usable input signal.

4. Try swapping out the preamp, or use a better quality preamp.

5. Try using a more sensitive microphone, like a powered condenser design, instead of a dynamic or ribbon mic.

Try to get a useable signal while keeping that preamp input knob at around noon on the dial, and you’ll get much cleaner recordings!