Recording Signal Level
Sat Jan 16, 2016
It's been a couple weeks since my last post on this subject. I've been recording vocals for two songs and taking note of the process.
Alright, I've got the mic in position and I've got my headphones ready to go. I'm ready to record vocals. My next focus is on the recording level.
I first started recording using a Panasonic tape recorder. Then I bought a boom-box that recorded as well. My first mic was a cheap little thing from Radioshack. I would record something onto the cassette deck then play it back and record into the boom-box by positioning the microphone to pick up the cassette speaker and whatever live part I was doing next. Background noise was a problem to say the least. I tried to record the loudness signal in order to reduce the background noise. Later I bought a Fostex 4-track tape deck and a little Yamaha mixer. Here I also tried getting the loudest recording I could. In each situation if the signal was too loud I could hear distortion. So I'd back off the mic or turn down the mixer channel to reduce it. When I went digital and bought Pro Tools (I started at version 3) I carried over the same philosophy, as loud as possible. As I learned more and more about digital recording and mixing I discovered this is not ideal.
In a nutshell you can't make a signal louder than 0db in digital. A higher signal will create distortion. If -3db was the target for the loudest level in analog, -18db is the target in digital. This provides some headroom between -18 and 0 to allow for spikes in the signal. For example a slapping bass note. The initial attack may be very strong and quick. You may not see it on the meter. You'll see a level as the note rings but it may not represent the transient.
Another reason for needed headroom is mixing. When multiple tracks are played back those signals are added together. It doesn't take long to find out you need to pull down a lot of faders when mix buses are distorting. Pro Tools' faders allow for finer adjustments when the fader is positioning around zero. When you pull it down 7-15db it's difficult to get move it in fractions of a db.
This applies to anything being recorded. Specifically with vocals, I know I'll be increasing the level in the box when I start adding EQ and compression. Again, having the headroom allows me to add these processors and keep the fader level hovering around 0.
Alright, so if you recall I've got a mic plugged in to a mic preamp. The preamp is plugged into my Avid MBox Pro. The MBox allows their mic pre-amp to be bypassed by using an insert cable to connect my preamp in the back of the unit.
I've adjusted the gain so the signal is riding between the green and yellow leds, usually on the yellow side for vocals. I took a quick look through the manual. I didn't see it but I believe this area is centered around -18db.
I've played around with the headphone volume to get it where I want. Ready to press the record button and start tracking.