User manual

P1 Audio Processor User Manual Page 41
Answers to some common questions;
Q. Why don’t 24 bit soundcards achieve their theoretical 144dB
dynamic range in practice?
A. The highest audio signal level which most 24 bit A/D chips
can handle is around +7dBu limited by the +5V supply
voltage which these chips are designed to run from (not to be
confused with the soundcard’s maximum input level which is
often much higher but this is simply fed through an analogue
level attenuator to the actual A/D chip).
The lowest audio signal level which an A/D chip can resolve
is limited by two main factors;
The noise floor of the analogue input circuitry.
The problems of sampling very low voltage levels accurately.
These last two factors usually determine the level at which
the dither noise is added to the digitally sampled audio signal
and this in turn sets the soundcard’s noise floor.
So there are practical issues which limit both the maximum
and minimum signal level which the A/D converter can work
with and these limit the dynamic range achievable in
practice.
Q. Why don’t you offer a higher output dynamic range in the P1
processor?
A. There are two factors which set the output dynamic range of
the P1;
Remembering that the P1’s maximum output is limited to
prevent digital clipping of your recording device;
Increasing the limiter’s natural threshold above 0db (+7dBu)
would decrease the available input headroom (set at 14dB)
as we worked closer and closer to the P1’s own maximum