8
Metering
ISA One’s front panel provides three level meters: a traditional
moving-coil VU meter – which shows the average volume
level, plus two peak-reading LED bargraphs – which indicate
dBFS, ie., the level in dB, relative to maximum output (when
the red ‘0’ LED illuminates).
The VU meter and the left Input LED bargraph are linked and both indicate the main signal
(the
selected Input, post Gain & Filter)
at the point set by the status of the Post Insert switch:
• Post Insert Switch Off – The VU and Input LEDs indicate the signal level at the Insert Send
connector. This will also be the Main O/P when the Insert switch is off.
• Post Insert Switch On – The VU and Input LEDs now indicate the signal level at the Insert Return
connector. This will also be the Main O/P when the Insert switch is on.
The right DI/Ext bargraph indicates the level at one of two different signal locations, determined by
the presence of a jack at the rear Ext I/P socket:
• Ext I/P unused – The right LED meter indicates the level at the DI O/P connector.
• Ext I/P jack inserted – The right LED meter now indicates the level at the external input.
Metering the A-D Inputs
The two inputs to the A-D option card are fed from; Ch.1: the Main O/P; Ch.2: the Ext I/P.
With the Ext I/P jack connected – and the left LED meter indicating the Main O/P
(see above)
– the LED
bargraphs will display both signals being sent to the A-D card inputs.
At default calibration, LED ‘0’ indicates a signal level of 22 dBu, which is the maximum input level of the A-D card.
Meter Calibration
The calibration of the VU and LED meters can be adjusted using trim controls on the rear panel. Note
that changes to the VU meter calibration will only take effect by pressing the VU Cal switch.
• VU Meter – The default VU meter lineup (VU Cal switch off) is 0 VU = 4 dBu.
With the VU Cal switch on, rotating the VU Meter Cal knob will set the value at between
0 VU = 11 dBu (fully anti-clockwise) and 0 VU = 26 dBu (fully clockwise), with 0 VU =
22 dBu at the centre detent position.
• LED Meters – The default setting of 0 dBFS = 22 dBu occurs when the knob is in its
central detent position
– to correspond with the maximum input level of the A-D card.
Rotating the Peak Meter Cal knob will set the value at between 0 dBFS = 15 dBu (fully
anti-clockwise) and 0 dBFS = 26 dBu (fully clockwise).
