Everyone in the recording industry talks about the sound of transformers, and vintage gear is still used in every major studio mainly because of the wonderful properties of tubes and audio transformers. Talking specifically about output balancing transformers, they tend to not only give the sound a particular coloration (most of the time a desired one), but they also create the perfect true servo balanced output only if the ground connection on the output jack (usually pin 1 of an XLR plug) is taken in consideration.
It is very important to use true balanced connections on devices that contain audio transformers on their inputs or outputs. And if an unbalanced connection is required (for some odd reason), make sure you ground the unused pin of that connection. For example:
A mic-pre like the Neve 1073 would have a transformer on it’s output. If the XLR cable used on the output of it looses let’s say pin 3 (the negative or inverted signal in a balanced connection) normally you would expect about 6dB of level loss. Not that big of a deal right?...Wrong! Not only would you lose useful signal, and decrease your S/N Ratio (Signal to Noise Ratio) but also the whole frequency response would change. You would lose most of the low frequencies depending on what kind of a gear you are going in to after the 1073. The reason for that is because the transformer on the output really would not have much to do with the ground of the device. When you lose one of the active pins on a balanced connection (pin 2 or 3 of the XLR) all you have left is one active pin and the ground. In a sense you would be trying to sort of bypass the transformer and “mess” with the audio before it hits the output transformer, because ground is usually present in the primary winding of an output transformer and not really connected to the secondary – (final output) of the transformer. That of course is not always the case but if you end up with a super week signal with no low end coming out of your Neve mic pre, check your cables first before you take it apart.
Balanced audio Connections http://en.wikipedia.org/wiki/Balanced_audio
Primary winding http://www.thefreedictionary.com/primary+winding