User Manual
7
THE LINE INPUT
The Line Input is a balanced female XLR jack (Pin 2 hot). As previously mentioned, the MICROPHONE
XLR inputs can double as line inputs due to the unusual headroom they exhibit, but we also included
dedicated line inputs with separate jacks and a position on the input gain to select them. Electronically,
there is very little difference except between the Mic and Line inputs except that the Mic inputs have
much more gain available and the Line inputs have one less gain stage if minimalism is a concern or
phantom power might be dangerous.
THE LINE OUTPUT
The output stage is also similar to that of the 5088 console, using high voltage class-A discrete circuitry,
driving a carefully congured output transformer that can deliver a full +25dBu from the balanced and
ground-free secondary winding.
This maximum output level provides a large margin over and above the likely maximum
requirement of any destination equipment to which the channel module may be connected. This is
especially true when feeding digital equipment!
Freedom from the interference elds that are inevitably present in any control room is virtually
guaranteed by the balanced, ground-free design used in the Channel Strip. 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 amplier
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
This pair of jacks are only used to perform some ne 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 the Portico II 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