Evert wrote:
>Hi Klas
>
>The configuration is a non-inverting opamp configuration. The lo/hi
>switch only switches between 5 or 50 times amplification, no other
>circuitry is used, I checked the service manual to make sure.
>
Yes, and when you use a the 50 times amplification, the headroom of the
op-amp is much lower.
(Glossary: Headroom: How large an input signal can be accepted before
distortion/clipping occurs.)
>When is the selfnoise of an opamp the lowest, at high gain or at low
>gain (closest to unity gain)
At high-gain, generally.
The best way (theoretically) is to use the input op-amp at maximum gain,
(lowest value of the resistor) and attenuate the signal before it reaches
the input stage. However, listening to a modern MD, it doesn't seem to
matter much if you use High or Low settings.
The noise you hear (mostly) come from the microphone, NOT the input
amplifier. It is only when you use low-sensitive mic's that the input amp
noise will be audible. You can't use a dynamic microphone with a modern MD.
for example. ME62 and 67, as well as all Telinga mic's have quite sufficient
sensitivity.
Klas.
Telinga Microphones, Botarbo,
S-748 96 Tobo, Sweden.
Phone & fax int + 295 310 01
email:
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