Behringer MX1604A User Manual download pdf (Page 21)

EURORACK MX1604A

+ Care should be taken NOT to plug mics into the console (or stagebox) while the Phantom

Power is on. Also, mute the monitor/PA speakers when turning Phantom Power on or off.

Allow the system to adjust for a couple of seconds after engaging phantom power before

setting input gains.

8.3 Looming problems

Loom wiring is an art unto itself, and it is worth taking time out to get it right. First off, it is important to avoid

earth loops. (A looped wire acts an aerial, picking up hum and 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 some-

where.

A good suggestion is to ensure that all screens are commoned at the mixer. 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. Keep both the earth and screen connected at the

amplifier. The MX1604A will then be earthed via the amplifier. This wiring method is certainly not the only one

but it usually works best.

Some quality equipment has an independent signal and mains earth. In this case at least one screen should

carry earth to the equipment. Sometimes the only way to find out is to experiment.

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 sleeve for all balanced jack sockets

connected to unbalanced equipment, you could use balanced patch leads throughout. There is no benefit in

wiring a balanced output to a balanced input with a mono patch cord.

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!

8. CONNECTIONS

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Behringer MX1604A User Manual Page 21