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• Tips on Acoustics for Your Home Studio
• Frequently Asked Questions from Voice Talent
• Tips on ISDN, 2 3
• Tips on Wiring Your Home Studio, 2 3
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• Recirculating grounds cause hum. To keep recirculating grounds from occurring, you should develop some sort of rule to keep only ONE interconnect cable as a ground path from a piece of equipment. In the following examples, you are instructed to connect the ground lead to the ground pin on both ends of the cable you are making. But when you have perhaps 4 cables connecting to a piece of gear (left, right, in and out) and all the cables make the ground connection complete, you have 4 paths ground can follow. This causes problems called recirculating current which causes hum. You should establish only ONE path ground can follow between any two pieces of equipment. To solve this issue, either leave ALL grounds lifted on the unbalanced gear and use a star ground system or adopt one cable that always makes the ground connection (like left input) and lift the rest on the unbalanced end.
• When making cables, use wire designed for balanced connections even though you are mixing the two. Balanced wire has a positive lead, a negative lead and a drain or shield wire. Pick a color common to all the wires you are using that can represent the positive lead and use that color for the positive lead throughout.
• Cables that connect balanced and unbalanced equipment are not wired the same for either direction. For example, when feeding unbalanced input with an balanced output, you might use a cable with and RCA connector and a TRS (stereo phone) connector. That same cable should not be used to go the other way feeding balanced input with an unbalanced output. This should be kept in mind not only when building cables but when buying cables. See this diagram for the differences.
• When feeding a balanced output to an unbalanced input - On the balanced connector, connect the positive wire to the positive pin, the shield wire and the negative wire to the ground pin. On the unbalanced connector, connect the positive wire to the tip pin and the negative wire to the shield pin. Don't connect the shield wire at the unbalanced connector. It's best to shrink wrap the shield to keep it from accidentally touching anything.
• When feeding a transformer or "servo" balanced output to an unbalanced input - On the balanced connector, connect the positive wire to the positive pin, the shield wire to the ground pin and the negative wire to the negative pin. Install a small jumper wire between the ground and negative pins on the balanced connector. On the unbalanced connector, connect the positive wire to the tip pin and the negative wire to the shield pin. Don't connect the shield wire at the unbalanced connector. It's best to shrink wrap the shield to keep it from accidentally touching anything. (Most balanced equipment outputs are NOT transformer or "servo" balanced. Consult your manual to see.)
• When feeding an unbalanced output to an balanced input - On the unbalanced end, connect the positive lead to the tip and the negative lead to the shield pin. On the balanced end, connect the positive lead to the positive pin, the negative lead to the negative pin that the shield lead to the ground pin.
• When feeding a unbalanced output to and unbalanced input - connect the positive lead to the tip on both ends. Connect the negative lead and the shield lead to the ground pin on the output side and connect only the negative lead to the ground pin on the destination end of the cable leaving the shield lifted. CAVEAT: As mentioned above, to eliminate recirculating grounds, lift the shield AND the negative leads on the destination end for all but ONE cable going between two devices.
• When feeding a balanced output to an balanced input - just do it! This is the best and most trouble-free way to interconnect equipment. Connect the positive lead to the positive pin, the negative lead to the negative pin. Again, to reduce recirculating grounds, you should only connect the shield on one end and float it on the other on all but one cable.