Behringer EURODESK SX4882 User Manual download pdf (Page 18)

18 EURODESK SX4882 User Manual

◊ With an LF cut at 100 Hz and a low shelf boost at 80 to 160 Hz, you have

pretty much got a peak response rather than shelving at the bottom.

◊ Look at the extraordinary width of the frequency sweep of the upper

mid EQ -300 Hz all the way up. Set to maximum boost and play about

with the frequency in real time. We bet you’ll get some stunning filter

sweeps. Try it on drumloops – great for dance music!

◊ You can cascade channel EQs by connecting the DIRECT OUT

(see section 7 “Connections”) of one channel into the LINE or TAPE

INPUT of another. The first channel should first be un-routed to all

buses, including L/R and aux sends. The second channel then becomes

the “control” channel, routing to the buses. You now have a 23- channel

mixer, but one channel has a 4-band (semi)-parametric plus 30 dB of

shelving swing!

◊ Remember EQ contouring can be done with CUT as well as BOOST.

E.g.: cutting away the top and bottom, then pushing up the gain is

equivalent to MID-RANGE BOOST! EQ is NOT a 1-way street!

◊ Always re-set a channel’s input gain after altering the amount of

EQ cut or boost applied (see 3.3).

10. Gain Optimization

PFL (Pre-Fader-Listening) is the way to set a desk level. Setting up the channel

input gain is discussed in the essential section13. Optimum master aux send

levels will be dependent on the sensitivity of the FX device being driven,

butunity gain is a useful starting point. As the mix progresses, more and more

channels are likely to be sending to eects via the aux buses, and it’s best to

PFLall sends (aux, su/jointfilesconvert/347833/bgroup, MIX-B) just before setting up for the nal mix.

Outboard reverbs etc. should all be made to work hard. There’s no point in having

an 85 dB dynamic range if the input meter of your reverb is barely ickering.

On the other hand, digital distortion is not one of the nicer noises around.

Fortunately you can SOLO the FX returns. Here you’ll have to rely on your ears

to detect digital distortion, since dierent outboard processors calibrate their

meters dierently, and their dynamic range is not sucient to allow, say, 15dBof

headroom (as is the case with DAT etc.). The PFL/SOLO meter, on the other hand,

looks only at the desk’s analog aux input level, if you hear distortion, but the

meter says you’re just hitting 0 dB, then it must be coming from the aux send

amp or the FX unit. If PFL on the aux send reveals nothing amiss, turn down the

input on the FX unit, and turn up the desk’s aux return.

◊ 99 times out of 100 distortion in the aux send > FX > aux return loop

will come from the FX unit (FX GAIN TOO HIGH), and the same goes for a

high noise level (FX GAIN TOO LOW).

◊ Noisy FX (or synth) returns can be greatly improved by the addition

of single-ended noise reduction between FX output and aux

(or channel) returns.

◊ We found out that using analog single ended noise reduction can

help warm the sound of certain digital reverbs which sound too cold/

metallic, and also give that “Echoplex” sound to digital delay decays.

◊ Analog multitrack tape should be driven quite hard, since its dynamic

range (without noise reduction) is likely to be 20 to 30 dB worse than

other elements in the recording chain. Try to record bright. You can

always mix back duller. Brightening up an off-tape signal will bring up

the level of tape noise.

◊ When mixing or recording, keep the channel FADER levels around or

below 0 dB. If you do find the faders creeping up or down, apply a

suitable offset over all channel faders, and try to control your bad habit

in future!

11. Impedances and Tuning

Electronic inputs tend to have impedances measured in tens of kiloOhms.

Outputs, on the other hand, are generally two or three orders of magnitude less.

This is just as well, otherwise a signal at an output might nd that the line of

least resistance is the limit of the preceding unit.

In the patchbay section we recommended that you parallel the MAIN MIX

output of the EURODESK SX4882 into all 2-track recording inputs. It would not

do any harm to buer each output from the primary one (i.e. that feeding into

your most expensive DAT recorder or 1/2” mastering machine) with a 470 Ohm

resistor. Cassette, DAT and reel to reel recorders’ input impedances should be

similar, butjust in case they aren’t, it is better to add a fraction of a dB of thermal

noise to the inputs of the secondary recorders in the shape of a resistor, rather

than having an unusually low impedance input grabbing most of the signal.

Anotherneat idea is to parallel the Monitor L/R output via a 47 kOhm resistor

pair. Now you can safely connect e.g. a tuner to either extra hole, without

shifting the stereo image (this would happen if a low impedance tuner input was

connected directly across one side of the monitor output). Now, whenever you

monitor an instrument’s input level with the PFL/SOLO function, you can check

its tuning also. That should impress the customers. Especially those using old,

unstable, butvery desirable analog synths.

All output / input pairs normalised!

Fig. 11.1: Resistor-buered parallel wiring for bay 8 (see section8 “The patcheld”)

12. (Un)balanced Lines

Balanced inputs and outputs are oered on most audio connections on the

EURODESK SX4882 (inserts and direct outs being the major exceptions).

Why? Though all audio cables (except speaker cables) have earthed screens,

the shielding they aord from the electromagnetic garbage that permeates

the atmosphere is never perfect. The balanced line is a simple but eective

mechanism to overcome this problem. Instead of one insulated audio

conductor, two, usually twisted together, are contained within a single screen.

Oneconductor, wired to pin 2 of an XLR-type connector by international

convention (after decades of total confusion!) carries a signal variously referred to

as “hot” or“positive”. Pin 3 is wired to the “cold” or “negative” conductor.

What does this mean? Consider an unbalanced line. Now, that’s much easier

to understand. You have one “hot” or “positive” core, and an earthed screen.

The “hot” wire’s waveform, if looked at on an oscilloscope, would be directly

correlated to the audio signal waveform. If you looked closely at the trace,

you‘dsee random noise along the X axis. What you probably wouldn’t see,

however, is any superposition of 50, 100 Hz, etc. corresponding to mains hum

interference, since these frequencies would be tangled up in the audio signal

(to spot them visually you’d need to perform a FOURIER TRANSFORM). AC mains

frequency and its overtones are picked up by any wire, and some will always leak

through a cable screen. The question is, when does it become audible?

Well, all other things being equal, the amount of mains hum picked up by a cable

is independent of the signal level. Speaker lines run 50 or more volts, enough to

diminish the eect of mains radiation to vanishingly small even with no screen.

(In fact, at these voltages another eect comes into play: capacitiveresistance.

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Behringer EURODESK SX4882 User Manual Page 18

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