[Arny Krueger]

"David Nebenzahl" wrote in message
.com

I'd say that since a differential amp practically
eliminates common-mode noise, there's no reason *not* to
use one (which, after all, was the question the OP asked).

Transformers are an effective means of elimination common-mode noise. They
are as a rule more effective than differential amplifiers. If you have an
input transformer, you don't need a differential input and you pick up some
inherent protection against EMI and casualty losses.

If you've ever had a grounding problem that a standard active differential
input can't handle, you know what I mean.

Trnasformers also provide galvanic isolation, or isolation of signal
ground. We would probably be a little less critical of the configuration of
safety grounds in audio if we were still in the days of transformers.

Transformers would probably rule the inputs of professional grade gear were
it not for costs. While it is hard to make transformers have as flat of
frequency response and as have ultimately low distortion as differential
inputs, it is possible to make them perform well enough to be sonically
innocious.

Transformers are still the preferred means for obtaining the best possible
freedom from grounding problems in areas where the cost issues are not so
severe, such as analog and digital communications.