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More on cable wiring – balanced to unbalanced

Today we’ll temporarily conclude our thread on cable wiring with suggestions on how to wire balanced outputs into unbalanced inputs. We’ve spent the past few inSync issues detailing exact cable wiring diagrams so hopefully by now we can spare you the drawings and discuss concepts because we have a lot to cover today and limited space for it.

When connecting balanced outputs to unbalanced inputs the big question that must come up with what to do with that third wire? It’s generally pretty straight forward when connecting unbalanced gear to balanced gear (see yesterday’s TTOTD), but when the output device is balanced there are a variety of ways to get into trouble. As always we recommend you consult the manuals that come with your equipment, as they will often tell you how to do it for best results on their gear. Of course just as often they say nothing about it.

So we’ll go about making some generalizations. In “most” cases, when the exact characteristics of the balanced output are unknown you are best to leave the negative (pin 3, or Ring) wire unconnected at the unbalanced input. So (in a pin 2 hot device), pin 2 would connect to the tip (positive) and pin 1 (shield) connects to the sleeve (negative).

This is the preferred default because some devices object very strongly to having either the positive or negative pin tied to ground or shield. You’ll rarely damage any equipment by doing this, but sometimes the resulting output will become almost non existent and very distorted. Basically, it won’t work.

The one sure exception to the floating pin 3 scenario is with transformer balanced outputs. Transformers need to have both the positive and negative connected to complete the circuit, so in those cases you must tie the negative to ground at the unbalanced end. In those cases we prefer to float the shield at that end to prevent it from becoming a signal carrier.

Actually there are many other situations where connecting the negative and floating the shield at the unbalanced end work better. But this gets into an area where you have to consider larger numbers of variables than we have the space to explore here. All I can say at this point is that at Sweetwater we have the expertise to dig in to these potentially complex situations with you and work out the best wiring scheme for your application. This is just another aspect of the Sweetwater difference.

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