In addition to the generally preferred sound of analog to digital converters running 6 to 12 dB below maximum levels, other reasons to keep levels below maximum are:
• Often, clip indicators don’t indicate clipping unless several consecutive samples are
“over” – by which time the problem is more serious than a single sample being over.
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• This also means that if a single sample is clipped, but multiple samples in a row do not, the clip will not be indicated. Just because it doesn’t show up, doesn’t mean it hasn’t happened and distorted the sound.
A big difference between competing digital recording devices and systems is how they distort when overloaded. Some are more sonically forgiving than others. You can expect a cheap device to produce ugly clicks and chirps immediately on clipping, while you might be able to get away with the occasional and light clip on a more expensive, better quality device.
On an analog device, with a dBV peak meter, the level can happily be pushed past “0,” and into the “+” values. On many analog devices, more of the unit’s real character will be picked up by doing just that. Care must be taken not to light any “over” light though!
A VU needle type meter cannot show you peak level, so good levels peaking at, or just above “0” are appropriate for less percussive sounds, and lower for more percussive sounds.
Again – the “peak” light should not come on.
With good input levels established, it should be easy to get good levels to the recording device.
FROM THE MIXER TO THE RECORDING DEVICE
Mixer outputs to the recording system may be pre-fader or fader, and pre-panner or post-panner. If they are post-fader and/or post-panner, faders in-between the pre-amps and outputs to the recorder should be set at unity (which is marked “0” near the top of the fader’s travel), and pan controls should be set correctly if odd/even panning rules apply to the outputs in use.
• In its unity position, a fader does not boost or cut the level of the signal on that channel. What leaves the channel is the same level as was set at the input gain/pre-amp stage – possibly minus a few dB depending upon the output being used, because of the stereo panning laws used to maintain perceived equal amplitudes when a sound is panned to different positions. (When a sound is panned centrally for example, two loudspeakers reproduce it – that’s twice as much power than if it was hard panned and only reproduced by one loudspeaker. Panning laws attenuate the sound’s amplitude slightly as it is panned towards center so that it is perceived at equal amplitude regard-less of where it is panned.)
• Turning a fader above unity also turns up mixer channel noise. If a channel needs turning up above unity, it usually implies that the input gain is too low, so the input level to the channel should be checked.
• Turning a fader down below unity is fine during mixing, but if post-fader sends to the recording device are used during tracking, low levels will be sent to the recorder.
When mixing, good main/master output levels can be achieved by setting the faders for the most important, loudest channels of the mix at around unity, and other faders below unity. If too
many faders are set above unity, the main output levels can be too high, clipped, or overloaded;
or noisy, due to the additional amplification applied by faders that are above unity. Conversely, running too many faders too low will result in low main/master output levels and an increased relative percentage of noise. A compensating gain increase will be required in the next record-ing device that, while turnrecord-ing up the desired signal, will also turn up the undesired extra noise.
1.16 ANALOG AUDIO CONNECTORS
Microphones and all of the equipment in the recording chain diagram (Figure 1.18) need to be plugged in and connected together correctly. You need specific cables to do this, so you need to know the names of the connectors used, and what each type of connector is commonly used for.
XLR CONNECTORS
XLR connectors are the preferred connectors for single channel analog connections. They are robust and lock into place – a little release button needs to be pushed to disconnect them. They can be found with varying numbers of pins in the connector. Three-pin connectors are usually Fi g u r e 1.19 Left: Good input levels and good unity gain output levels on the top device produce good input levels on the bottom device. Right: Low input levels and undesirable fader gain on the top device, and increased input gain on the bottom device results in a more noisy signal, due to the two additional stages of amplification after the top device’s input gain.
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CHANNEL FADER and MAIN OUT FADER at"0"dB, unity
OUTPUT LEVEL METER
INPUT LEVEL METER INPUT GAIN
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f
CHANNEL FADER and MAIN OUT FADERabove unity
" + N O ISE"
OUTPUT LEVEL METER
1
INPUT LEVEL METER INPUT GAIN
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" + N O ISE"
used for standard audio connections. XLR connectors can be male or female – the male plug is the one with the pins, the female (jack) the one with little holes. Signal always flows out of the male and into the female, so if you’re ever wondering “which end do I need,” think about signal flow – if you’re connecting to the output of a device (outputs always have a male connector) you need the female end of the cable, and if you’re connecting to an input (inputs are always female) you need the end of a cable with a male plug. XLR connectors are most commonly used for mic connections, and many line level connections on a lot of professional equipment.
QUARTER-INCH PHONE CONNECTORS
Quarter-inch phone connectors are also used on a lot of audio equipment. They come in two types:
• quarter-inch TRS connectors have three segments to the connector – the tip, ring, and sleeve.
• quarter-inch TS connectors have just two segments to the connector – the tip and sleeve.
Quarter-inch connectors come in male and female sexes – the male plugs and the female jacks.
The genders of quarter-inch connectors are not dedicated to inputs or outputs like XLR con-nectors – sound can go in or out of a male plug or female jack.
Line level connections commonly use quarter-inch TRS connectors. Instrument level, stan-dard “instrument cables,” and some speaker level connections use quarter-inch TS connectors.
From the outside, all female quarter-inch jack sockets – instrument, line or speaker level, TRS or TS – look identical, so it’s really important to know what you’re hooking up and use a cable with the correct connectors and wire for the job! You don’t want to fry a mixer channel by connecting a speaker level output to a line level input!
Fi g u r e 1. 2 0 XLR Connectors. Top: Male. Bottom: Female.