Focusrite ISA Two Rackmount 2-Channel Microphone Preamp - Manual (Page 8)

8
English
Mode 1: Mic Gain Range 0-30
With the 30-60 switch (3) off, the stepped Gain control operates over a gain range of 0 dB to +30
dB, the gain setting being indicated on the front panel by the outer arc of numbers around the Gain
control.
Mode 2: Mic Gain Range 30-60
With the 30-60 switch (3) on (illuminated), the stepped gain dial operates over a gain range of +30 dB
to +60 dB, the gain setting being indicated on the front panel by the outer arc of numbers around the
gain knob. An additional 20 dB of gain can be applied to the signal after the mic/line stepped gain
control using the Trim control (4). (See Trim control text below for a full explanation).
Line Input Gain (2)
With the line input selected, the user has access to gain settings from –20 dB to +10 dB in 10 dB
steps, indicated on the front panel by the inner arc of numbers around the stepped gain knob. The
30-60 switch (3) is inactive when the line input is selected. An additional 20 dB of gain can be applied
to the signal after the stepped mic/line gain using the Trim control (4). (See the Trim control text
below for a full explanation.)
Trim - Mic or Line Modes (4)
The Trim control provides additional gain of up to +20 dB when mic or line inputs are selected. The
level of trim chosen is indicated on the front panel by the inner arc of numbers around the trim
knob. The additional 20 dB of gain that can be applied to the mic or line signal is very useful for two
reasons:
• When high gain is required - using trim in conjunction with a mic gain of +60 dB gives a
maximum available gain of +80 dB, making it very useful for getting good digital recording
levels from very low output dynamic and ribbon microphones.
• Gain adjustment during recording - when small amounts of gain adjustment are needed to
correct performance level variations during recording, use the Trim control rather than the
stepped mic/line Gain control, as switching the 10 dB gain steps would be too intrusive. It is
therefore good practice to apply some trim before using the 10 dB stepped gain control to find
the optimum recording level so that the Trim control can be used to gently add or reduce gain
later, if so required.
Trim - Inst Input Mode (4)
The Trim control provides variable gain of +10 dB to +40 dB when instrument mode is selected. The
level of trim chosen is indicated on the front panel by the outer arc of numbers around the Trim
control. Please note that the stepped Gain control (2) is not active in instrument mode, and gain is
only provided by the Trim control.
+48V (5)
Pressing the +48V switch (illuminated when active) provides phantom power, as required by
condenser microphones, at the rear panel XLR microphone connector. If you are unsure whether
your microphone requires phantom power, refer to its handbook, as it is possible to damage some
microphones (most notably ribbon microphones) by applying phantom power to them.