TC Electronic M5000, User Manual, Page: 99 / 203

ALGORITHMS
M5AMBIEN
Rev 1.2 Page 28
12dB/oct. Cut filters are switchable between 12dB/oct maximally flat amplitude (Butterworth)
or flat group delay (Bessel) types. The parametric equalizer features a natural and well defined
bandwidth behavior at all gain and width settings.
Fig.2 The bandwidth of the parametric EQ is expressed Fig.3 The bandwidth of the notch filter is defined at its
in octaves and is defined at half the eq gain -3dB points.
Shelving and parametric filters are with a 100% symmetrical boost/cut response, i.e. a
positive setting in one band can be canceled exactly by another with the same negative gain
setting (using the same frequency and bandwidth settings).
All equalizer settings can be changed ‘on the fly’ with no unnatural audible artifacts. A fast
acting morphing technique naturally transforms any eq setting into another (including EQ type
and on/off selections). The morph time is fixed.
All filters are minimum phase types, i.e. there is a unique relationship between the amplitude
and the phase response of the filters.
The filters are done in extended resolution implementations with active noise shaping that
forces errors at the 48th bit level further towards zero.
DITHERING:
As all processing inside the M5000 is done with a higher bit resolution than e.g. a CD or a
DAT normally is capable of storing, when leaving the M5000, we are normally faced with the
fact that we have too many bits. Just throwing away the bits e.g. below the 16th bit level,
which will cause a graininess in the audio (and a quite objectionable distortion at low signal
levels). If instead, a more intelligent form of ‘throw away bits’ processing is used, it is
possible to eliminate these artifacts, and to some extend, it is even possible to obtain an audio
resolution exceeding the 16 bits of the target storage medium.
The technique is simply to add a very slight amount of well controlled noise to the audio
signal. This added noise will then cause the otherwise very signal dependent error signal (the
thrown away bits) to loose all relations to the audio signal itself, i.e. the distortion is turned
into signal independent noise. If we look at the resulting behavior of the least significant bits
we may realize that they suddenly become very busy. In fact, on the average, they will tend to