Setting the recording level control in GarageBand
We're not equipment snobs here at Audio Masterclass. We just want to hear great audio, and whatever equipment or software you use to get great results is fine by us. So if you have a Macintosh computer and want to use a DAW that costs $0.00 (i.e. free!) then GarageBand could be a good choice. Several of our students have used GarageBand and we have had no issues at all with the quality of the audio they achieved.
There are however two issues that have come up more than once. The first is how you connect a microphone to record into GarageBand...
How to connect a microphone to record into GarageBand
The answer to this might seem obvious. But to the person who is likely to choose GarageBand as their DAW, it perhaps isn't so. Apple positions GarageBand as a fun piece of software for people who want to have a go at making music on their computer. Someone like this may never even have heard of an XLR connector, let alone an audio interface. So they use a mic with a minijack on the end of the cable and connect directly to their computer.
Now this might be OK for podcasts and the like, but it isn't OK for pro audio and Audio Masterclass offers no support for this way of working. The reason it isn't OK is that the signal from a microphone is delicate and needs careful amplification by a specialized microphone preamplifier. If a microphone is connected to a general-purpose input, then the audio quality will suffer, particularly in terms of signal-to-noise ratio. Indeed, we have heard recordings made this way with absolutely terrible noise problems. There may also be problems with headroom, leading to distortion, with high-level sound sources.
So to resolve this problem it is absolutely essential to record into GarageBand using an audio interface with an integrated microphone preamplifier. This preamplifier must have an XLR input connector and it also must have phantom power available. (Of course you can also use a separate microphone preamplifier with a line-level only audio interface, but with equipment like this you almost certainly wouldn't be using GarageBand.)
Why an XLR connector?
Why an XLR connector? Well, other connectors could be used. XLR connectors have several advantages, but the key point is that XLR connectors are only ever used on pro audio equipment. They are never used in domestic audio or general-purpose computer audio. If a manufacturer uses an XLR input, it demonstrates that they are targeting the pro audio market and that their product is very likely to be fully usable for that purpose.
Why phantom power?
Why phantom power, if you're using a dynamic mic that doesn't need it? The answer to this is that it's a 'why not?' for a manufacturer. Why not add phantom power when it's simple and cheap to do so? Why omit it and render a huge range of of capacitor microphones unusable with your product?
GarageBand's recording level control
GarageBand has a recording level control for the benefit of podcasters who record without an audio interface. Controlling level in software is fine, as long as the input signal has been optimized first, as it will be in an audio interface with an integrated microphone preamplifier (or separate microphone preamplifier and line-level audio interface). But connecting directly to the computer omits that important step. Even so, podcasters will get a useful degree of control with the recording level feature, at least for their purposes.
Other DAWs don't have this, so it removes the question you have to ask with GarageBand - if you have a gain control on your preamplifier, where should you set GarageBand's recording level control?
Actually the answer is quite easy - just leave it at 0 dB and forget about it. Setting it to a lower level will degrade your signal-to-noise ratio for no good purpose. If you need more headroom then turn down the gain on the preamplifier.
You can boost the signal level by up to 6 dB using GarageBand's recording level control. But if you have an external microphone preamplifier there seems to be no good reason to bother with this. If you were recording a very quiet source and had set the preamp's gain to maximum, then you might think that an extra 6 dB might come in handy. In reality, you would just get an extra 6 dB of background and electronic noise so it wouldn't be of any real benefit.
1. When recording from a microphone into GarageBand, then you should always use a microphone preamplifier and audio interface (which may be integrated into a single unit.)
2. Leave the recording level control in GarageBand at 0 dB and use the gain control on the microphone preamplifier to set the recording level.
This file was recorded into GarageBand with the recording level control at 0 dB. This file was recorded with the recording level control at +6 dB and the microphone gain set 6 dB lower to compensate. Both files are normalized for ease of comparison. Other than differences in delivery, there is very little to choose between them.