AD122-96 MX
Appendix III
18
Appendix III: AD122-96 MX Soft Saturation
The SOFT SATURATION feature provides a digital emulation of an ideal magnetic tape saturation
characteristic. The three available settings are:
1. SOFT SATURATION OFF: yields normal converter operation (see lower curve VOFF).
2. SOFT SATU3dB: provides a digital gain of 3dB for sample amplitudes below
-6dBFS and digital compression for amplitudes greater then -6dBFS (see middle curve V3dB).
3. SOFT SATU6dB: provides a digital gain of 6dB for sample amplitudes below
-12dBFS and digital compression for amplitudes greater then -12dBFS (see upper curve 6dB).
The graph below shows the three transfer functions. The plots show input versus output value between
-20dBFS and 0dBFS.
The algorithm for soft saturation is fundamentally different from classical audio compression. A
compression algorithm provides time varying gain as a function of signal power. The gain variations
are slowed down (attack and decay envelopes) to minimize distortions (a sudden step in signal gain
generates a time decaying distortion).
The soft saturation algorithm operates on a sample by sample basis. All sample values below a given
threshold (-6dBFS or -12dBFS) are amplified by a constant gain (+3dB or +6dB) and all sample values
above the threshold are reduced by a pre-assigned amount emulating ideal tape magnetization curve
(exponential function). While signal peaks get "pushed down" (peak signal distortions), the dynamic
performance for signals under the selected threshold stays intact.
