On Fri, 28 Apr 2006 09:40:45 -0000, Jasen Betts
wrote:

On 2006-04-26, Don Pearce wrote:
On Wed, 26 Apr 2006 13:13:24 +0100, "Dave Plowman (News)"
wrote:

In article ,
Don Pearce wrote:
In broadcasting the most common combination with balanced mics is an
approx 150-300 ohm output going into an about 1.2k input on the mixer.
Older STC ribbons were sometimes 30 ohms. Accurate 600 ohm matching
only really was used into very long lines. Like telephones. But most
long lines these days will be digital.

Shouldn't that be 12k in? A pair of 6.2k ohms in series feeding the
phantom power would give you that. Even with phantom switched off, the
resistors are still there, so the input impedance doesn't get any
higher for dynamics.

No - the phantom 'stand off' resistors don't go in series with the signal
path. They are from the plus side of the phantom supply to each leg of the
balanced input - very simply.

That's right - but from the point of view of the balanced signal, they
are in series, from one side to the other.

sound the two resistores in series are parallel with the input to me

Bye.
Jasen

The resistors are in series with each other, that combination is in
parallel with the input. Because the resistors are 6.2k, the
combination applies 12.4k as the maximum possible input impedance of a
microphone preamp.

d

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Pearce Consulting
http://www.pearce.uk.com