MacIntyre Music -- Tech Tips

Tech Tip #1 - Buzz free wiring for unbalanced systems

I've done a fair amount of research about the subject, talked to the tech at my repair place etc. Also I got my hands on the enclosed wiring diagram. So I thought I'd share what I've learned with you.

I'm working to implement these changes in my own place, by the way, and found them to be well worth the extra trouble.

Most buzzes and radio frequency interference (RFI) are caused by ground loops. As I understand it, the RF and line noise which is supposed to drain off in the shield of the wire gets recirculated when multiple units are connected together. It's like sitting in the barbers chair and looking at the mirrors across from each other. There are seemingly infinite reflections of the source image. Commercially available cable for unbalanced connections (i.e. RCA or phone plug connectors) is bi-directional, and so exacerbates the recirculation (or ground loop) problem. A design with balanced connectors offers protection against this problem, because signal ground and shielding are taken care of by two different wires. That's why they are more highly regarded and expensive.

In my experience, the solution to the ground loop problem, when you are using gear with unbalanced connectors, consists of the following 6 steps:

1) power source - try to get all your power for the studio from a single leg or circuit. When you use separate circuits, unless your power is extremely clean, you sometimes hear the difference in voltages between the two as audible hum at the frequency of the difference (often 60 Hz) in your studio electronics, a 15 or 20 amp breaker should easily handle your needs for the time being.

2) isolate all outboard gear, modules, etc. from metal rack rails or contact with other units (since signal grounds are sometimes routed to the chassis in an electrical device.) use duct tape, plastic spacers, etc. to accomplish this. Be especially sure to do this with your patch bays. (where all this stuff meets)

3) In the manner shown in the 3rd wiring diagram from the top, make custom cables for all ins and outs of analog devices utilizing tip/sleeve type connectors of any kind (RCA or 1/4" plugs). As you see from the diagram your custom cables are one directional. Always mark which end is which, and use 3 conductor cable (2 leads and a shield). Otherwise signal grounding and shielding have to take place in the same wire (not good). This is the procedure:

¥ On the output or transmitting end of the cable leave the shield disconnected, use the red lead for the plug tip and the black lead for the plug's sleeve connector.

¥ On the input or receiving end of the cable as before, use the red lead for the plug tip but connect the shield AND the black to the plug's sleeve connector.

4) In all cases, but particularly for speaker cables, use the shortest run of cable for the job.

5) Use large gauge speaker wire - 18 gauge or larger (larger gauges are lower numbers by the way). Regular lamp cord is fine. Keep in mind speakers sometimes hum in the presence of video monitors. (and therefore need to be repositioned)

6) Try to run different types of wires bundled in separate groups whenever possible. Keep, for instance, power cables bundled together in one group, and audio cabling in another. when they must cross, try to do so at right angles.

If all this custom wiring seems daunting as a single large project, try it on your noisiest piece of gear and work backwards, doing one piece of gear when you have the time. If your experience mirrors mine, you will be amazed at the quietness of gear you thought was chronically noisy. And you'll start to notice your system in general has more output and detail as your wiring improvements fall into place.

Hope this helps-


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