Hello Robert.

> I think you are assuming that the input signal to each preamp would be
> halved because the input impedances of the amps are now in parallel.
> This is a faulty analysis, though, and would only be true if the input
> impedance of the amplifier was comparable to the source impedance of
> the transducer.  In fact, the amplifier impedance can be _much_ higher
> than the transducer impedance.

  REALLY?  Well, in that case, wouldn't it be far more sensible to match
the impedance better by using a step-UP transformer before resorting to
parallel amplifiers?

  Hint:  That's how they do it in microphone pre-amplifiers.  They do
however not infrequently trade off poorer noise figure for lower cost
and/ or slightly flatter frequency response by omitting the transformer
and using a second pre-amp module to provide a balanced input.  This is
however, just that, a trade-off.

  Hmmm.  I thought I was replying to a list, but it turns out it was
direct.  You may care to redirect it or not, and I will reply to the
others.

  Cheers,
        Paul B.