18EURODESK SX4882 User Manual

Bay 8:

L7 & R8 equals the L/R recording input to the 2-tracks. On Bay 8 we have hard-wired these to recording outputs 1 to 6 in order to drive all recorders simultaneously. Copying from any 2-track source to all recorders may be done by patching the source outputs into L7 and R8.

We have assumed you have a HiFi amp available to enable a variety of secondary sources to be condensed into the XTRN (external) input for easy monitoring selection via the HiFi amp’s input selector switch, if you want to record from any of these sources, best patch direct from the individual outputs (17 to 22) rather than the HiFi amp mix (15 and 16) for the cleanest result. (The exception being vinyl, which will need to use the HiFi amp’s RIAA pre-amp to present the mixer with a flat response signal).

All output / input pairs normalised!

Fig. 8.4: Wiring for bay 8 (for advanced wiring scheme refer to section 11)

8.3 Looming problems

Loom wiring is an art in itself, and it is worth taking time out to get it right. First, it is important to avoid earth loops. (A looped wire acts as an arial, picking up electromagnetic radiation.) Think of a tree: Every part of that tree is connected to every other part, but only by one route. That’s how the total earth picture for your entire studio should look. Don’t take the earth off your power cable plug to reduce audible 50 Hz mains hum (or its harmonics). Rather you should be looking at disconnecting the signal screen somewhere.

You could do worse than ensure that all screens are commoned at the patchbay in which case all unearthed equipment would pick up earth from this point via a single screen (more than 1 route = an earth loop), while mains-earthed equipment would have all screens cut at the equipment end.

◊Some quality equipment has an independent signal and mains earth. In this case, at least one and possibly all screens should carry earth to the equipment. Sometimes the only way to find out is “suck and see”.

Take care to ensure that using the patchbay does not disturb the studio’s earth architecture. Always use short as possible patch leads with the screen connected at both ends.

If you’re really serious about hum levels, you could run balanced lines wherever appropriate. The earth wiring scheme would be the same as before. By shorting the ring to the barrel for all balanced jack sockets connected to unbalanced equipment, you could use balanced patch leads throughout. (There is no percentage in wiring a balanced output to a balanced input with a mono patch cord!) (See section 12 “(Un)balanced lines”.)

Having designed mains hum out of the system, make up your cable looms from the patchbays outwards, and use cable ties, flexible sheaths, multicores etc. to keep the back of your racks tidy. It’s going to get very busy in there, and loose cables will inevitably mean lost signals. Possibly even lost equipment!

9. Equalization

The variable parameters of the channel A and B equalizers on the EURODESK SX4882 are described in sections 3.4 and 3.7.

Few people buying the EURODESK will need to be told how an equalizer works. But how to get the best out of it? Well, that’s another story.

In the beginning EQ was an instrument for removing unwanted frequencies, or compensating for imperfect microphone response curves, or bumps in a studio’s acoustic. It was a corrective device. Tamla Motown turned that notion upside down in the sixties with the novel idea that you try to find for each instrument a characteristic frequency not shared by the other instruments in the mix. Then you whack up its gain. This makes individual voices punch through

a mix in a slightly unnatural but exciting way. In general, corrective EQ usually involves broadband (slope) contouring, together with narrowband notching of unwanted resonances. The narrower the notch or “Q”, the less the total signal will be affected.

◊Finding bad resonances is made easier by first frequency sweeping in boost mode.

“Motown” EQ is achieved by applying boost in a fairly broadband way.

The broader the band, the more musical but less instrument-specific the effect. Applying boost over a narrow bandwidth will sound “Honky”. The two semi- parametric bands of the EURODESK EQ have had their Q fixed at 1, a typical and sensible value. For sounds which require drastic corrective EQ (remember no MIDI instrument should need it), it is advisable to have a couple of channels of fully comprehensive equalization in your rack. (You can always bounce tracks though the outboard EQ, freeing up the unit for the next task). Check out our BEHRINGER ULTRACURVE PRO DEQ2496, which promises to be another price/ performance buster.

The EURODESK EQ might be applied to a signal as follows: First, trim the LF and HF shelves to achieve the required slope or “LOUDNESS”. (These controls mirror the tone controls of a typical HiFi amp.) Now use one parametric band to boost the nicest frequency, and another to cut the nastiest. Over all channels in the mix, if too many of the nicest frequencies coincide, then you might have to settle for second best in some cases! Often you might want to boost two nice frequencies. Really nasty frequencies will need notching. Time to go outboard.

Why does the upper mid bell frequency go up to 20 kHz? A more pertinent question might be, why has it taken so long to get there? After all, even 16 bit (the lowest acceptable quality) digital audio sports a 20k bandwidth: surely if

20k is important then so is controlling it. OK. You and I will never hear a pure 20k sine tone. However, Rupert Neve, the audiophile Guru, would argue that when it comes to real instruments, what happens even above 20k may have a perceptible effect on the listener. It seems that one reason why high- quality (1/2" at 30 IPS) analog tape sounds better than DAT to many discerning ears is because, although its frequency response begins to roll off at 12 dB/octave somewhere around 15 to 20 kHz, it is not abruptly cut off at 20!

We have heard, or “detected”, a 20+ kHz low pass filter being switched in and out when monitoring an analog master tape through a speaker system that included piezo-electric tweeter elements capable of reproducing up to 40 kHz. Perhaps less controversially it can be shown that if cut/boost is applied at 20 kHz, a significant portion of the resulting EQ curve for all but the tightest of Q’s actually occurs in the audible spectrum, below 16 to 18 kHz. For example if the BEHRINGER EQ is boosted by +15 dB at 20 kHz, the amount of boost at 10 kHz will be 3 dB. The resulting EQ curve will bear no relation to one where 3 dB of boost is applied at 10 kHz.

◊A good vocal signal can be enhanced by applying a significant boost in the 15 k region or higher, above the nasty sibilance region. Especially effective if you’ve got a de-esser post EQ.

◊Use the LF cut to tighten up channels in a mix: maybe remove it only for the bass, kick drum, toms, tablas, didgeridu and other deliberate subsonics. (When recording classical music ignore this advice).

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