Sonnox Oxford Restore - Manual (Page 15)

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The CPU usage in Para-EQ mode is dependent on the number of filter sections operative; this is
not the case in Comb mode. This is another reason why Para-EQ should be used with care with
a low frequency fundamental.
The Para-EQ filters offer several advantages over the Comb filter. The first is that you can
reduce the amount of attenuation as you increase in frequency. You use the Slope control to do
this.
Secondly, with Para-EQ mode you can choose to notch out only odd harmonics, or both odd and
even harmonics. Frequently you only need to remove odd harmonics, which will inflict less
damage to the signal.
Thirdly, Comb filters become less effective when the fundamental is at higher frequencies
(greater than around 2kHz), so Para-EQ mode is much better at the removal of loud whistles or
whines at higher frequencies.
4.4
Sensitivity Modes for Optimal Removal of Buzz
The correct setting for the Sensitivity control is crucial for best repair and least damage to the
original audio. There are two modes for using the Sensitivity control.
The Default Mode of Buzz removal
With the Sensitivity control fully clockwise (so most sensitive), the detection circuits will be
removing some elements of the signal as well as the buzz. As the sensitivity is reduced, fewer
signal elements will be removed from the audio signal and the quality of the repair will improve.
However, as the sensitivity is further reduced some elements of the buzz will also start to be
excluded from the removal circuits and the buzz will become audible. The best compromise is
with the sensitivity as low as possible while there is still no audible buzz in the signal output.
One way to illustrate this is by considering the Diff output. Auditioning the Diff output at full
sensitivity will reveal full buzz and some distorted signal. Reducing the sensitivity will reduce
the signal content, but will soon also start to change the tonality of the buzz. As you reduce the
sensitivity you are moving signal and buzz elements out of the Diff output into the Audio output.