The Røde NT-USB is a USB microphone. USB microphones have one major benefit: you don’t need a driver or an ADC (Analogue-Digital-Converter) to make it work. To get best results from a USB microphone you need to set the gain correctly. The NT-USB has an optimised gain for its internal circuits, but unless you have a loud voice, that gain setting may be too low. Here is how you set it for optimum results.
You’ll need a DAW (Digital Audio Station – music creation software) or an audio editor, a Røde NT-USB mic and a Mac for this setup walkthrough. Your DAW could be Logic Pro X, Reason or ProTools. As for audio editors, Audio Hijack is great, but Sony Sound Forge Pro 2 is better because it has more features that we can use for optimisation of the input signal.
I used Audio Engineering’s Spectre for metering, Logic Pro X and Sound Forge 2. The first thing we’ll need to do is connect the NT-USB to a USB port. If you have one available on your Mac, use that one. A direct connection is always preferred when working with audio equipment, but if you don’t have open USB ports, a hub will do fine too. I’m assuming you have your NT-USB mounted on its included mic stand with the pop filter in place.
Open OS X’s System Preferences panel and select the Sound tab. As soon as you connected the NT-USB, the microphone appeared in both the Inout and Outout tabs. By default, you’ll notice the gain setting for the Røde microphone to be identical as the setting for any microphone, i.e. at about 1/4.
Place the NT-USB at 15cm from your mouth. 15cm is about the distance between your little finger and your thumb, both stretched outwards. Now speak at a normal voice and look at the Input level. Not much will be happening. The gain is too low if you don’t speak in a loud voice. We can fix that by cranking up the gain with the slider, but the System Preferences Input level display gives too little feedback to be of use.
The Audio MIDI Setup control panel of OS X isn’t going to help you either as that panel doesn’t have an input level gauge at all.
Hijack Audio Pro
If you have Audio Hijack on your system, open it now. In the Input tab, select Audio Device as Source Type and Røde NT-USB as Input Device. The blue input level meters should work when you speak into the microphone. But again, these level meters are only an indication that something is happening. We need more information than this.
Go to the Effects tab and select the VU Meters effect from the effects list (I’m assuming you know how to work Audio Hijack Pro — if you don’t, then read the manual first). The VU Meters let you boost the input gain, but if your voice is like mine, you’ll never get to a level that’s higher than -20dB.
You therefore will now increase the gain with the System Preferences. First reset the gain in the Audio Hijack Pro VU meters effect to its default setting. Switch to the System Preferences but keep the VU Meters somewhere you can see them. Now, drag the slider until you see the VU Meters move to about -20dB. On my system, this will be at about 3/4 of the maximum gain the OS X System Preferences Input level can be set.
In Audio Hijack Pro you can now increase the VU Meters gain to a level slightly higher than normal and you’ll have set your NT-USB microphone to the best level possible without clipping.
Logic Pro X
In Logic Pro X you have more options to increase gain, but the easiest and most simple is to crank up the Gain slider to about -4dB. You can also use several different effects and filters, but these will actually process your signal, not strengthen it. The only way you can strengthen the signal really is by increasing the slider.
Sony Sound Forge Pro 2
In Sound Forge Pro you don’t have much choice but to set the gain with the System Preferences panel only. This works the same as in Audio Hijack Pro, with one exception: you can arm the recording channels and set your Input level until the recording level meters in Sound Forge Pro reach the level you want.
Audio Engineering Spectre
If you have Audio Engineering’s Spectre — a full set of gorgeously designed professional-grade audio meters — you’re in luck, because these meters will allow you to set your NT-USB gain level to a “just right” setting. In fact, when using Spectre, you can perhaps better use the Audio MIDI control panel as it allows for more granular control over the gain levels of your microphone.
There’s no need to write down the level settings, unless you want to make absolutely sure you have them for later reference. OS X’s Audio MIDI control panel as well as the System Preferences Sound panel save your settings and even if you disconnect the NT-USB to reconnect later, the panel will restore them to your preferred settings.
Your gain level should be at -10dB to -5dB. Why not go all the way to 0dB? Because that’s an invitation to background noise as well as clipping with every ‘p’ or ‘t’ you pronounce.