However, the preamp design is optimised for low noise with this

mismatch. This is the difference between a straight impedance match and a
noise optimum impedance match.

The ultimate check is to record at a higher recorder level setting in a ver=
y
quiet place, or possibly under a pile of bedclothes, and look at the hiss
spectrum. If it tips up above 5KHz, this could be the thermal noise of the=

air (rising at 3dB per octave) which sets the lowest noise threshold anyway=
.
This fundamental noise level of course is chopped off by the "A" curve, but=

we can hear it at high gain settings. If this test works, it is the only wa=
y
to bypass reality over theory. :-)

David Brinicombe