STEP TWO: OPERATE AT UNITY

Definition of Unity

Unity is the optimal operating level of a given system.

It’s vital that the sound entering the mixer, passing through the mixer, and exiting the mixer is at a level that best suits the mixer’s circuitry. This is called unity , and we always want to dial in the mixer’s settings and operate within the mixer’s unity range. Operating outside this range can add hiss or hum to a recording.

Unity is achieved by adjusting channel volume, master gain, pre-amp attenuator (PAD), or channel gain (trim), and properly metering. Take your time here, and make sure you can operate your mixer at unity.

Figure 4.9

Figure 4.10

The only time to adjust the master gain is when you engage the tone oscillator for calibration. Some mixers will continue to send signal from the channel inputs when the tone oscillator is engaged. So, by turning the master gain fully counterclock-wise to the “off” position, any open mics will be muted, keeping tone clean for calibrating. Most mixers will mute all channel inputs when the tone oscillator is engaged.

Adjusting the Channel Fader

Each channel fader has a unity range or area that the mixer operates at its quiet-est. On a studio console this is indicated with a shaded area on the channel fader. We poor souls in the fi eld have to fi gure it out for ourselves. The channel fader unity range is commonly found between 12 o’clock and 3 o’clock. You should operate in this area.

See Figure 4.12 . Figure 4.11

Adjusting the Master Gain

I start here because the master gain is a “set-and-forget” dial. It will have a

“0” setting and will probably have a détente at this spot. As you might recall from Chapter 3 , détente is a notch so you can set it exactly every time. The “0” setting is not “Off” but the unity output gain of your mixer. Set it here and leave it alone. See Figure 4.11

If you operate your mixer with the channel fader below the unity range (let’s say 10 o’clock), the recording will seem dull and the mixer may add bottom frequency hum. If the channel fader is set above the unity range (let’s say 4 o’clock), the mixer will start adding hiss as you push the mixer beyond its unity range.

Proper Metering

The meters are your visual representation of the sound as it passes through your mixer. You need to know where they should be reading to stay within the mixer’s unity range.

If your mixer has PPM meters (PPM meters have a “dB” symbol), you want to operate between –2 and +8. This is quite hot—which I’ll explain later. See Figure 4.13 .

Figure 4.12

Figure 4.13

Figure 4.14 Mixer with pre-amp attenuator

If the mixer has VU meters (VU meters have a “VU” symbol), you want to operate between –4 and +2—again, a very hot signal.

Setting the Pre-Amp Attenuator (PAD) or Channel Gain

With all the information necessary regarding channel unity and meter unity, we can fi nally start making adjustments to the mixer. As defi ned earlier, when a sound source enters the mixer from a mic, you need to make sure that it is at a level or volume that the mixer can handle. Depending on the type of mixer you are using, it will use either a pre-amp attenuator (PAD) or channel gain (trim) to increase or decrease the level of signal entering the mixer’s pre-amp.

Mixers with a pre-amp attenuator (Pad) adjust as follows:

1. Plug a mic into XLR Input 1.

2. Set the master fader to “0” or Unity.

3. Set CH1 PAD to “0.”

4. Ask talent to speak at performance level.

5. Starting with the CH1 fader at unity, slowly increase the volume until the needle is bouncing within the meter’s unity range (between –2 and +8 on a PPM meter). If the CH1 fader ends up within the channel fader unity range (12 o’clock to 3 o’clock), you are golden. The mixer is ready to go, and you can start operating.

6. If talent starts talking and the needles are beyond the meter’s unity range, you will need to adjust the PAD. Switch it from “0 dB” to “–10dB.” This will decrease the amount of signal entering the mixer. If the addition of a –10dB PAD allows you to adjust CH1 fader within its unity range (between 12 o’clock and 3 o’clock), and the meters are between –2 and +8, you’re operating at unity and again, you’re golden.

If you still can’t increase CH1 fader up to the channel unity range without the needle going beyond the meter’s unity range, you’ll need to increase the PAD to

“–20dB.”

Mixers with a channel gain (trim) adjust as follows:

1. Plug a mic into XLR “Input 1.”

2. Set the master fader to “0” or unity.

3. Set CH1 fader around 1 o’clock.

4. Ask talent to talk at performance level.

Figure 4.15 Mixer with channel gains (trim)

Start with setting it to its lowest setting—usually 20Hz—and listen to the talent’s voice. Focus your listening on the low frequencies of his or her voice and not the ambi-ence. Switch the fi lter to its next higher setting (let’s say 100Hz), and listen if the fi lter cuts into the low frequencies of the voice. As you increase the high-pass fi lter (20Hz 5. Start with CH1 channel gain turned all the way left, and increase it until the needle is

bouncing within the meter’s unity range (between –2 and +8 on a PPM meter).

Think of the channel gain as “coarse” gain adjustment. Once the coarse adjustment is made, use the channel fader for fi ne adjustments during recording.