User Guide

HARDWARE FEATURES

Front Panel

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The front panel includes all the input gain and monitoring controls as well as two of the input

connectors for Mic, Line and Instrument signals.

1. Inputs 1 and 2 – Combo type input sockets - connect microphones, instruments (e.g., guitar),

or line level signals via XLR or ¼” (6.35 mm) jacks as appropriate. Either ¼” TRS (balanced)

or TS (unbalanced) jack plugs can be used for instruments or line level signals.

2. MIC 48V – two switches enabling 48 V phantom power at the XLR contacts of the Combo

connectors for mic inputs 1-4 and 5-8 respectively. (Note that inputs 3 to 8 are on the rear

panel.) The switches each have an associated red LED indicating that phantom power is

selected.

3. Gain 1 & 2 – adjust the input gain for the signals at Inputs 1 and 2 respectively.

4. INST – two switches changing the input conﬁguration for the jack contacts at Inputs 1 and

2. When INST is selected, the gain range and input impedance are altered (relative to LINE),

and the input is made unbalanced. This optimises it for the direct connection of instruments

(usually via a 2-pole (TS) jack plug). When INST is off, the inputs are suitable for the connection

of line level signals. Line level signals may be connected either in balanced form via a 3-pole

(TRS) jack or unbalanced via a 2-pole (TS) jack. The switches each have an associated red LED

indicating that INST is selected.

5. PAD – two switches which insert a 10 dB pad in the signal paths of Inputs 1 and 2. With the pad

applied, the maximum input signal level is +16 dBu. The switches each have an associated red

LED indicating that PAD is selected.

6. Gain 3 to 8 – adjust the input gain for the signals at Inputs 3 to 8 respectively. (Note that the

connectors for these inputs are on the rear panel.)

7. Input meters – eight 5-segment LED bargraph meters indicating the signal levels of the eight

analogue input signals. The meters show signal level after the input gain stage, and thus

their indication is affected by the gain controls. The LEDs illuminate at -42 (green, “signal

present”), -18 (green), -6 (green), -3 (yellow) and 0 dBFS (red). A level of 0 dBFS implies digital

clipping, and should always be avoided.

8. USB active LED – a green LED which illuminates when the unit is recognised by the computer

to which it is connected.

9. Locked – a green LED which conﬁrms clock synchronisation, either to the Scarlett 18i20’s

internal clock or to an external digital input.