Rupert Neve Portico II - Master Buss Processor - Manual (Page 5)

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This maximum level provides a large margin over and above the likely maximum
requirement of any destination equipment to which the module may be connected. This is
especially true when feeding digital equipment!
Freedom from the interference fields that are inevitably present in any control room is virtually
guaranteed by the balanced, ground-free design used in the MBP. The classic Rupert Neve designed
modules always used transformers, as do a number of other high quality vintage modules still in current
use.
High quality transformer connectivity has been used for many years, enabling modular amplifier
units to deliver the sonic performance for which they are famous. The outputs are very appropriate for
driving unusually long lines that may be needed when used remotely.
Bear in mind that human ears are very sensitive and can perceive incredibly minute interference
signals that are not part of the “desired” signal. If unbalanced connections are used, great care must
be exercised to avoid ground loops and common signal paths. Reduced immunity from various
forms of interference can be tolerated (sometimes) but usually results in a loss of that transparent
musical resolution that we all love.
However, the output of any Portico II transformer-coupled XLR may be used with one side
grounded if necessary, for example to use with “Hi-Fi”, “consumer” or other unbalanced audio
gear, without degrading the performance of such devices. Care must be exercised when using
ancillary equipment to avoid overloading it.
THE SIDE CHAIN INSERT JACKS
These pairs of jacks are only used to perform some fine tuning of the compressor operation. The audio
that normally controls the compressor is available on the “SIDECHAIN OUTPUT” jack. One can take
this audio and pass it through an external equalizer then return it back to the “SIDECHAIN INPUT”
jack. Now changes on the external EQ affect the sensitivity of the compressor. For example, if you cut
some low frequencies on the external EQ, then the compressor will tend to not want to reduce the gain
as much on bass notes. This is not the same thing as simply boosting lows on an equalizer, because the
latter changes the frequency response while the former changes levels. Similarly, one could boost highs
(6kHz for example) on the external EQ and cause the compressor to be extra-sensitive to that part of the
spectrum which happens to correspond with sibilance (esses). This can act as one type of a de-esser that
pulls down the volume of the whole signal if it senses an “ess”.
A few notes about these jacks. They are unbalanced and ideally best suited to be used with unbalanced
equipment. However most balanced EQ’s will work fine interfaced to these jacks. The simple symptom
of a balanced / unbalanced mismatch is that the “compression meter” will indicate a significant change
of compression depth (like zero) when the EQ is set flat. Keep in mind that nobody hears this signal path
so that any old nasty sounding EQ you tossed in a closet years ago might be perfectly suited for a side
chain insert task.
A NOTE ON DISTORTION
The human hearing system is a remarkably complex mechanism and we seem to be learning more
details about its workings all the time. For example, Oohashi demonstrated that arbitrarily filtering out
ultrasonic information that is generally considered above our hearing range had a measurable effect on