Blue 315
Isomorphic Mastering Equaliser
The extreme left side of the panel houses switches for Eq In/Out and Power, apart from these the
two channels, mounted one above the other, are identical as are their controls. Starting from the
right hand side of the module:
Input Level sensitivity is controlled by three sets of rotary controls, first a rotary switch for the
course sensitivity with 5dB steps, secondly another rotary switch for the fine sensitivity in _dB
steps and finally a continuously variable control with ±1dB range which is only in circuit when the
Vari push switch has been pressed and is illuminated.
The first section of the Eq is for the High frequency section. This has a shelving characteristic of
the Baxandall variety with switched rotary controls for both frequency , boost and cut .
The next two section, HMF and LMF are identical except for their frequency ranges. All the
controls on these fully parametric stages are multiposition rotary switches. The boost and cut
controls have the same sensitivity as the HF section, with frequency and bandwidth switches for
each stage.
The last section of the Eq is the mirror of the first, the LF section is another shelving stage with
rotary switches for both boost , cut and frequency selection .
There are two further rotary switches for the High and Low pass filters, with a fixed slope rate and
switched selection of turnover frequency.
Below the filter switches there is a Phase Reverse switch and an Overload indicator, which will
light whenever the signal level reaches or e20dB, which is 6dB prior to the onset of
clipping.
The left hand end of the panel houses two further large push switches, the uppermost of these is
the Power switch, which is lit when the unit is active.
The lower large push switch is the Eq In/Out switch . This has two modes of operation, the switch
will latch, electronically, when pushed putting the Eq in-circuit and light the LED, a further push
will unlatch and take the EQ out and the module back to bypass (this is a relay bypass). An
alternative mode is to press and hold the switch, with gives a momentary action to the Eq In state
which will become bypass when the switch is released. This allows the In/Out switching to be
stable and momentary from the same switch.
