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Mic input impedance (Z In) selection
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Selects the high (30-60 dB) mic gain range on the Gain switch
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10 dB stepped Mic/ Line Gain switch Mic: 0-30 / 30-60 Line: -20 +10
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Filter roll-off frequency pot
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Applies the variable-frequency high-pass Filter to the selected input
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Switches the external Insert return into the channel path
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Input Trim pot Mic/Line: 0 +20 dB Instrument: +10 +40 dB
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Applies +48V phantom power to the mic input XLR
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Inverts polarity (Phase) of the selected input
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Input source selection
The Input button selects the input source for the main channel path: Mic/Line/Instrument.
Pressing Phase inverts the polarity of the selected input. This can be useful when multiple mics are used in close proximity (ie., on a drum kit).
The Gain switch adjusts the mic gain in 10 dB steps. Its range is either 0–30 dB or 30–60 dB when the 30–60 switch is pressed. An additional 0–20 dB of continuous gain adjustment is available using the Trim control.
Caution
To avoid an excessive jump in level, It is recommended that the stepped Gain switch is turned to minimum before pressing the 30-60 switch.
Before starting a recording, set the Trim control to near its centre position. This will allow for some gradual gain adjustment up or down without the use of the stepped control.
Pressing the +48V button applies phantom power to the Mic input XLR. This switch does not affect the Line or Instrument inputs.
If you are unsure whether your microphone requires phantom power please refer to its handbook. Certain microphones (most notably ribbon and unbalanced mics) could be damaged by applying phantom power.
The Gain switch adjusts the gain between -20 dB and +10 dB in 10 dB steps. Continuous gain adjustment of up to 20 dB can be added using the Trim control.
The Instrument input is via a standard 1/4” mono jack (DI) on the front panel. The level is set using the Trim control and is continuously adjustable from +10 dB to +40 dB.
With the Mic input selected, pressing the Z In button steps through the four transformer preamp input impedance options. The values are shown in the table.
Tip
For information on impedance selection see Preamp Input Impedance.
The Line input impedance is fixed at 10 kΩ and is not affected by the Z In switch.
Pressing the Filter button inserts the 18 dB/octave high-pass filter into the channel path; it is applied to whichever input is selected. The High Pass Filter control allows the roll-off frequency to be set within the 16 Hz to 420 Hz range.
Tip
The filter is useful for removing any unwanted low frequencies, eg., rumble transmitted through floor-mounted mic stands, etc.
Pressing Insert places the Insert Return signal into the channel path before the Output connector, allowing the inclusion of external effects units.
The Insert Send is always available and is post the input Gain and Filter & Phase controls.
The LED meters indicate the level at the channel output connectors. The scale is in dBFS, ie., the level in dB, relative to maximum output (reached when the ‘0’ LED illuminates).
The default calibration is for ‘0’ to indicate a signal level of 22 dBu
The level at which the ‘0’ LED illuminates can be adjusted using the Peak Meter Calibration pot on the rear panel. The default setting of 0 dBFS = 22 dBu occurs when the knob is in its central, detent position.
Rotating the pot sets the value between 0 dBFS = 16 dBu (fully anticlockwise) and 0 dBFS = 24 dBu (fully clockwise).
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Mains inlet
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Insert Send and Return
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Channel Output
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Line input
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Mic input
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Meter calibration trim pot
Standard IEC receptacle for AC mains. ISA Two features a ‘Universal’ PSU, enabling it to operate on any supply voltage between 100 and 240 V AC
Balanced 1/4” TRS Jack sockets for Insert Send and Return. The insert can be added to the channel path by pressing the front panel Insert switch
Adjusts the level at which the channel meter ‘0’ LED illuminates. See page Meter Calibration.