Setting Up - Chapter 1
When to use Balanced Connectors
There are three options for connecting analog audio to the Q20: 1/4Ó unbalanced, 1/4Ó balanced (TRS) and XLR balanced. If your source and destination use balanced connectors, you should try to stay balanced throughout the chain. Balanced cables have a higher signal level and have the ability to cancel out hum and noise, which can make your mixes quieter. XLR connectors have the added bonus of locking into place, a good idea if you need to move your effects rack from place to place.
Keeping this in mind, your order of preference when connecting the Q20 to a mixer should be to use the XLR connectors first, then to use balanced 1/4Ó cables, then unbalanced 1/4Ó cables if your mixer doesnÕt have balanced sends and receives.
Avoiding Ground Loops
In todayÕs complex studio there are many opportunities for ground loop problems to occur. These show up as hums, buzzes or sometimes radio reception, and can occur if a piece of equipment ÒseesÓ two or more different paths to ground. While there are methods to virtually eliminate ground loops and stray radio frequency interference, most of the professional methods are expensive and involve installing a separate power source just for the sound system. Here are some easy helpful hints that a professional studio installer might use to zap those stray hums and buzzes.
➀KEEP ALL ELECTRONICS OF THE SOUND SYSTEM ON THE SAME AC ELECTRICAL CIRCUIT. Most stray hums and buzzes happen as a result of different parts of the sound system being plugged into outlets of different AC circuits. If any noise generating devices such as air conditioners, refrigerators, neon lights, etc., are already plugged into one of these circuits, you then have a perfect condition for stray buzzes. Since most electronic devices of a sound system donÕt require a lot of current (except power amplifiers), itÕs usually safe to run a
➁KEEP AUDIO WIRING AS FAR AWAY FROM AC WIRING AS POSSIBLE. Many hums come from audio cabling being too near AC wiring. If a hum occurs, try moving the audio wiring around to see if the hum ceases or diminishes. If itÕs not possible to separate the audio and AC wiring in some instances, make sure that the audio wires donÕt run parallel to any AC wire (they should only cross at right angles, if possible).
➂TO ELIMINATE HUM IF THE ABOVE HAS FAILED:
A)Disconnect the power from all outboard devices and tape machines except for the mixer and control room monitor power amp.
B ) Plug in each tape machine and outboard effects device one at a time. If possible, flip the polarity of the plug of each device (turn it around in the socket) until the quietest position is found.
C)Make sure that all of the audio cables are in good working order. Cables with a detached ground wire will cause a very loud hum!!
D)Keep all cables as short as possible, especially in unbalanced circuits.
If the basic experiments donÕt uncover the source of the problem, consult your dealer or technician trained in proper studio grounding techniques. In some cases, a Òstar groundingÓ scheme must be used, with the mixer at the center of the star providing the shield ground on telescoping shields, which do NOT connect to the chassis ground of other equipment in the system.
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