[LAD] Half-OT: Fader mapping - was - Ardour MIDI tracer

Fons Adriaensen fons at linuxaudio.org
Sun Aug 24 15:25:24 UTC 2014

On Sun, Aug 24, 2014 at 07:19:11AM -0700, Len Ovens wrote:

> That is true and for most studio mics (anyone use crystal mics?) it
> would be minimal. Anytime eq is used to bring back low level
> frequencies, it is likely to bring back the noise around that
> frequency too. Instrument pickups are most sensitive to this. I have
> a classical guitar that I put a piezo into.

Piezos have a capacitive impedance, together with the preamp resistive
input impedance this forms a first order highpass filter. A typical mic
input is around 2 kOhms, this would place the cutoff frequency somewhere
in the high audio range, with 6 dB/oct below that. Could be EQ'd in theory,
but for musical use it's usually better to use a high-Z preamp.

Some specialised preamps (e.g. for piezo hydrophones), actually do use
a 'zero impedance' input, and integrate the signal to compensate. This
provides the best FR and the most stable calibration, and allows the use
of very long cables.. 



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