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Inputs 1 and 2 – “Combo” input sockets - connect microphones, instruments (e.g., guitar), or line level signals here. Combo sockets accept both XLR and ¼” (6.35 mm) jacks. Microphones connect using XLR plugs: instruments and line level signals connect via ¼” (6.35 mm) jack plugs of either TS or TRS type. The preamp gain is appropriate for microphones when an XLR plug is inserted, and for higher level signals when a jack plug is inserted. Do not connect anything other than a microphone - e.g., the output of a sound module or FX unit - via an XLR plug, as the signal level overloads the preamp, resulting in distortion; , if phantom power is enabled, you may damage your equipment.
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Inputs 3 and 4 – XLR Combo type input sockets – as [1], but accept mic or line level signals only. Direct connection of instruments should be via Inputs 1 and/or 2.
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48V – two switches enabling 48 V phantom power at the XLR contacts (mic inputs) of the Combo connectors, in pairs (1 & 2; 3 & 4). The 48V indicators illuminate red when phantom power is selected.
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GAIN 1 to GAIN 4 - adjust the input gain for the signals at Inputs 1 to 4 respectively. The gain controls have tricolour LED ‘rings’ to confirm signal level: green indicates an input level of at least -24 dBFS (i.e., ‘signal present’), the ring turns amber at -6 dBFS to indicate the signal is close to clipping, and red at 0 dBFS (digital clipping).
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INST – the input type for the jack at Inputs 1 and 2 can be selected in Focusrite Control. The red LEDs illuminate when INST is selected. With INST 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 (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.
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AIR – four yellow LEDs indicating selection of AIR mode for Inputs 1 to 4. AIR mode, selected from Focusrite Control, modifies the frequency response of the input stage to model the classic, transformer-based Focusrite ISA microphone preamps.
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PAD – four green LEDs; illuminate when PAD is selected from Focusrite Control for Inputs 1 to 4. PAD decreases the signal level going to your DAW by 10 dB; use when the input source has a high level.
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USB LED - a green LED illuminates when the Scarlett is connected and recognised by your computer.
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ALT – when Speaker Switching is activated via Focusrite Control, the main monitor mix is diverted from LINE OUTPUTS 1 and 2 to LINE OUTPUTS 3 and 4. Connect a pair of secondary monitor speakers to the LINE OUTPUTS 3 and 4, and select ALT to switch between your main monitors and the secondary pair. ‘ALT’ illuminates green when selected. This function may also be selected from Focusrite Control.
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MIDI LED – a green LED illuminates when MIDI data is received at the MIDI IN port.
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MONITOR - main monitor output level control - normally adjusts the level at Outputs 1 and 2 on the rear panel, but follows selection of ALT mode. It also controls the level of any other outputs assigned to Hardware Control in Focusrite Control.
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- Connect one or two pairs of stereo headphones at the two ¼” (6.25 mm) TRS jack sockets below the headphone volume controls 1 and 2. The headphone outputs have independent mixes and carry the signals currently routed to Headphone outputs 1 and 2 (outputs 5 & 6 and 7 & 8 as stereo pairs) respectively in Focusrite Control.
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LINE INPUTS 5 to 8 – the inputs are balanced, on ¼” (6.35 mm) jack sockets. Connect further line level sources here, using either ¼” TRS (balanced) or TS (unbalanced) jack plugs.
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LINE OUTPUTS 1 to 4 – four balanced analogue line outputs on ¼” (6.35 mm) jack sockets; use TRS jacks for a balanced connection or TS jacks for unbalanced. Outputs 1 and 2 will normally be used to drive the primary monitoring system, though the signals available at any of these outputs may be defined in Focusrite Control. Outputs 3 and 4 can be used for driving alternative speakers (i.e., midfield, nearfield, etc.), or to drive outboard FX processors.
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OPTICAL INPUT – TOSLINK connector, able to carry eight channels of digital audio in ADAT format at 44.1/48 kHz sample rate or four channels at 88.2/96 kHz. These are additional inputs (13 to 20) to the Scarlett 18i8 3rd Gen. The optical input can also be used as an S/PDIF input if you need to connect equipment with an optical S/PDIF output. Note that the optical input is disabled when sample rates of 176.4/192 kHz are in use.
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MIDI IN and MIDI OUT – standard 5-pin DIN sockets for connection of external MIDI equipment. The Scarlett 18i8 3rd Gen acts as a MIDI interface, allowing MIDI data to/from your computer to be distributed to additional MIDI devices.
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S/PDIF IN and OUT – two phono (RCA) sockets carrying two-channel digital audio signals in and out of the Scarlett 18i8 3rd Gen in S/PDIF format. Like all the other inputs and outputs, signals at these connectors may be routed in Focusrite Control.
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External DC power input – power the Scarlett 18i8 3rd Gen via the separate AC adaptor (PSU) supplied with the unit. Note that the Scarlett 18i8 3rd Gen cannot be powered via its USB port from the host computer.
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Power On/Off switch.
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K (Kensington security slot) – secure your Scarlett 18i8 3rd Gen to a suitable structure if desired.
Your Scarlett 18i8 3rd Gen should be powered from an external 12 V DC, 1 A mains adaptor. A suitable adaptor is supplied with the unit.
Important
We recommend you only use the supplied mains adaptor. Failure to use this adaptor is likely to permanently damage the unit.
USB Port Types: The Scarlett 18i8 3rd Gen has a single Type C USB 2.0 port (on the rear panel). Once the software installation is complete, connect the Scarlett 18i8 3rd Gen to your computer; if your computer has a Type A USB port, use the Type A-to-Type C USB cable provided with the unit. If your computer has a Type C USB port, please obtain a Type C-to-Type C cable from a computer supplier.
USB Standards: Note that because the Scarlett 18i8 3rd Gen is a USB 2.0 device, the USB connection requires a USB 2.0 compliant port on your computer. It will not operate with USB 1.0/1.1 ports: however, a USB 3.0 port will support a USB 2.0 device.
When the USB cable has been connected, turn the Scarlett 18i8 3rd Gen on with the rear panel power switch.
The Scarlett 18i8 3rd Gen is compatible with any Windows-based DAW that supports ASIO or WDM or any Mac-based DAW that uses Core Audio. After following the Getting Started procedure, you can start using your Scarlett 18i8 3rd Gen with the DAW of your choice.
Please note - your DAW may not automatically select the Scarlett 18i8 3rd Gen as its default I/O device. You must manually select Focusrite USB ASIO as the driver on your DAW’s Audio Setup* page. Please refer to your DAW’s documentation (or Help files) if you are unsure where to select the ASIO/ Core Audio driver. The example below shows the correct configuration in the Ableton Live Lite Preferences panel (Windows version shown).
*Typical name. Terminology may differ between DAWs.
Once the Scarlett 18i8 3rd Gen is set as the preferred Audio Device* in your DAW, all inputs, and outputs appear in your DAW’s Audio I/O preferences. Depending on your DAW, you may need to enable certain inputs or outputs before use.
The two examples below show two inputs and two outputs enabled in Ableton Live's Input and Output Config pages.
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*Typical name. Terminology may differ between DAWs.
Two additional inputs, inputs 11/12 are listed in the Input Config page of your DAW’s I/O Preferences. These are virtual “loopback” inputs within software, not additional physical inputs. You can use Loopback to record DAW tracks from sources within your computer, e.g., from a web browser. Focusrite Control incudes a Loopback 1-2 mix tab, where you can choose which inputs to record.
Full details of how to use the loopback inputs can be found in the Focusrite Control User Guide.
The Scarlett 18i8 3rd Gen is an excellent choice for several different recording and monitoring applications. Some typical configurations are shown below.
This setup shows a configuration for recording a group of musicians with DAW software on a computer. Inputs 1 and 2 are used for two guitars, while Inputs 3 and 4 are used for vocals. Two stereo keyboards are connected to Inputs 5 to 8 at the rear. During recording, playback of the DAW can be monitored on the loudspeakers (if they are in a separate room – otherwise use headphones), and Focusrite Control can be configured to provide each vocalist with their own dedicated headphone mix. This can consist of any mix of themselves, the other singer, the guitars and keyboards, plus any other DAW tracks that may have already been recorded.
The front panel input sockets are XLR Combo type, which accept either a male XLR connector (you will have one on the end of your microphone cable) or a ¼” (6.35 mm) jack plug. Note the Scarlett 18i8 3rd Gen has no “Mic/line” switch – the preamplifier stage is automatically configured for a microphone when you plug an XLR into the input, and for a line or instrument when you connect a jack plug. Select INST in Focusrite Control (on the Device Settings page) if you are connecting a musical instrument (like a guitar) via an ordinary 2-pole guitar jack. INST should be off if you are connecting a line level source, such as the balanced output of an external audio mixer via a 3-pole (TRS) jack.
Note
The Combo connector accepts both types of jack plug.
If you are using condenser microphones, press the 48V button to supply phantom power to the mics. (In the example, this would be the 48V button for Inputs 3 and 4.) Most modern microphones of other types, e.g., dynamic or ribbon, will not be damaged by the inadvertent application of phantom power, but note that some older mics may be; if you have any doubt, please check the specification of your mic to ensure it is safe to use.
Input channels 1 to 4 of the Scarlett 18i8 3rd Gen each have a PAD function: when selected from Focusrite Control (PAD illuminates green when active), the signal level fed to your DAW is reduced by 10 dB. You will find this useful if the output level of your source is particularly “hot”, when you might notice clipping or the gain halo turning red, even at minimum gain.
You will frequently hear the term “latency” used in connection with digital audio systems. In the case of the simple DAW recording application described above, latency will be the time it takes for your input signals to pass through your computer and audio software, and back out again via your audio interface.
While not an issue for most simple recording situations, under some circumstances, latency can be a problem for a performer who wishes to record while monitoring their input signals. This might be the case if you need to increase the size of your DAW’s recording buffer, which could be necessary when you record overdubs on a particularly large project using many DAW tracks, software instruments and FX plugins.
Common symptoms of a buffer setting too low could be glitching audio (clicks and pops), or a particularly high CPU load within your DAW (most DAWs have CPU readouts). If you experience this on a Mac, you can raise the buffer size from the DAW itself. On Windows, you most likely need to change this from the ASIO Control Panel, which can usually be accessed from your DAW Setup Preferences*.
The Scarlett 18i8 3rd Gen, with Focusrite Control, allows zero latency monitoring, which overcomes this problem. You can route your input signals directly to the Scarlett 18i8 3rd Gen’s headphone and line outputs. This enables the musicians to hear themselves with ultra-low latency – i.e., effectively in “real time” – along with the computer playback. The input signals to the computer are not affected in any way by this setting. However, note that any effects being added to the live instruments by software plug-ins will not be heard in the headphones, although the FX will still be present on the recording.
When monitoring your inputs through Focusrite Control, ensure your DAW software is not set to route any inputs (what you are currently recording) to any outputs. If it is, the musicians will hear themselves “twice”, with one signal audibly delayed as an echo.
* Typical name. Terminology may differ between DAWs.
The 1/4” LINE OUTPUTS 1 and 2 jacks on the rear panel will normally be used to send audio to monitoring speakers. Active monitors have internal amplifiers with a volume control, and may be connected directly. Passive loudspeakers will require a separate stereo amplifier; the rear panel outputs should be connected to the amplifier’s inputs.
Connecting active speakers:
Connecting passive speakers with a stereo amplifier:
All the line output connectors are 3-pole (TRS) ¼” (6.35 mm) jack sockets, and are electronically balanced. Typical consumer (hi-fi) amplifiers and small powered monitors will probably have unbalanced inputs, either on phono (RCA) sockets, or via a 3.5 mm 3-pole jack plug intended for direct connection to a computer. In either case, use a cable with jack plugs at one end.
Professional active monitors and professional power amplifiers will generally have balanced inputs.
LINE OUTPUTS 1 to 4 incorporate “anti-thump” circuitry to protect your speakers if the Scarlett 18i8 3rd Gen is turned on while the speakers (and amplifier if used) are connected and active.
Caution
You run the risk of creating an audio feedback loop if loudspeakers are active at the same time as a microphone! We recommend you always turn off (or turn down) monitoring loudspeakers while recording, and use headphones when overdubbing.
The Scarlett 18i8 3rd Gen’s ALT function makes adding a second pair of monitors easy: connect the second pair to LINE OUTPUTS 3 and 4. After enabling Speaker Switching in Focusrite Control, you can switch between your main monitors and the secondary pair by clicking on the on-screen MAIN and ALT buttons. When ALT is active, the main mix output will be fed to the LINE OUTPUTS 3 and 4 instead of 1 and 2, and the green ALT LED will light to confirm this.
Note
As you switch between MAIN and ALT, the Line Outputs feeding the pair of speakers not in use are muted. When Speaker Switching is disabled, Line Outputs 1 to 4 are all initially muted (for safety); you need to unmute the appropriate outputs in Focusrite Control. Please see the Focusrite Control manual for more details of Speaker Switching.
In addition to the eight analogue inputs, the Scarlett 18i8 3rd Gen has an optical ADAT input port which can provide an additional eight audio inputs at 44.1/48 kHz sample rate or four at 88.2/96 kHz. (Note that the optical ADAT input port does not support 176.4/192 kHz sample rates.) Using a separate eight-channel microphone preamplifier equipped with an ADAT output – such as the Focusrite Scarlett OctoPre – provides a simple and excellent method of expanding the Scarlett 18i8 3rd Gen’s input capability.
The Scarlett OctoPre’s ADAT output is connected to the Scarlett 18i8 3rd Gen’s ADAT input with a single TOSLINK optical cable. To synchronise the devices, set the clock source of the Scarlett OctoPre to Internal and Scarlett 18i8 3rd Gen (via Focusrite Control) to ADAT.
Tip
When interconnecting two digital devices by any method, always ensure both are set to the same sample rate.
You can route the additional ADAT inputs realised using Focusrite Control in the same way as the other inputs. The additional inputs can form part of any musician’s headphone mix, as required.
The Scarlett 18i8 3rd Gen has the ability to store a mix configuration defined in Focusrite Control within the hardware. This feature lets you configure it – for example, as an on-stage keyboard mixer – using your computer, and upload the configuration to the device itself. Then you can use the Scarlett 18i8 3rd Gen as a simple local mixer as part of your keyboard rig to control the overall mix of multiple keyboards.
In the example shown, three stereo synthesisers are connected to the inputs of the Scarlett 18i8 3rd Gen; the Monitor Outputs go to the main PA system. You can adjust the gain for two of the keyboards against the third from the front panel; you can also adjust the overall level of the keyboard mix.
Using the digital connections on the Scarlett 18i8 3rd Gen 3rd gen, S/PDIF, it is possible to use it as a two- channel standalone preamp.
You can connect two input sources to any of the inputs on the Scarlett (microphone, line or inst) and using Focusrite Control you can route the analogue inputs directly to the S/PDIF outputs. Then you can connect the S/PDIF output to the S/PDIF input on another interface to expand that interface’s channel count, for example a second Scarlett 18i8 3rd Gen, or larger interface such as a Scarlett 18i20.