At 7:21 AM +0000 5/5/04, digidandy wrote:
>--- In Dan Dugan <> wrote:
>> This is not a valid test. Many good mic preamps will transmit
>> higher-than-normal noise when "unterminated," i.e. without a
>> low-impedance source connected.
>
>I know. But not using a mic shows the noise in its "cleanest", most
>stable state.
Not without terminating the input. An unterminated input may be
strongly influenced by the local RF field, not a stable thing at all.
>If I turn on the connected microphone the "aliasing" is
>still there - I have heard it in between loud sounds, and I have
>heard it "on top" of quiet sounds.
>
>Using a Sony ECM-MS957S, btw.
That's a rather noisy mike, maybe that's what you're hearing!
> > To test the self-noise of a mic preamp, solder 200-ohm resistors
>from
>> each channel to the shield in a mini-stereo plug. With that plugged
>> into the recorder you'll hear a more realistic example of the
>> recorder's noise performance.
>
>Thanks for the tip.
>
>I just find it strange that comparing my "mic-connected-but-turned-
>off" recordings with similar recordings from a Sharp MT-290 produces
>results in favour of the latter - which doesn't have
>the "aliasing"/quantising-like noise in the mid-range.
The behavior of improperly terminated inputs can be misleading in
relation to how they perform normally.
-Dan Dugan
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