User manual

Page 38 User manual P1 Audio Processor
being exercised and this only happens when you pump in the very
highest audio level which the converter will accept before digital
clipping. This level is called 0dBFS.
So, allowing our 12dB safety margin, a quiet vocal phrase may only
be peaking 20dB below this maximum safe level (down at -32dBFS).
In the analogue world this will makes no practical difference to the
achievable distortion, but in the digital world, lower levels into the A/D
means less bits representing the audio means more distortion.
Typically a -32dBFS signal will achieve a distortion performance of
around 0.01%. Not quite the dazzling figure quoted in the sound
card spec, is it? Once we get down to –60dBFS distortion degrades
to around 0.3%.
So there are audio performance advantages in getting a decent level
of audio into 24 bit digital recording systems. If your working 16 bit
then it’s even more critical.
How the P1 limiter manages dynamic range
Despite the claims of many soundcard and A/D chip manufacturers,
the usable dynamic range of most affordable 24 bit soundcards is
around 100dB. We define this as;
‘the difference in dB’s, measured RMS unweighted, between the
maximum signal which the soundcard can handle, called 0dBFS, and
the minimum tone level which is audible (not necessarily the same
level as the soundcard’s noise floor).’
Most soundcard manufacturers quote dynamic range in dBA which is
a weighted measuring scale taking into account the sensitivity of the
ear to different frequencies. It also happens to be a way of quoting a
higher dynamic range figure! Soundcard manufacturers also tend to
claim a higher dynamic range, claiming that the ear can detect sound
content which is buried far into the noise floor. The use of frequency
weighted digital dither has made such claims very fashionable but
many independent reviewers have questioned their validity.
It is desirable to manage dynamic range when recording because the
available dynamic range from recording sources such as