ISA C8X hardware features

Selecting a preamp channel allows you to adjust the channel's gain and preamp settings.

Select an ISA preamp

Select preamps 3 - 8

If you link channels, both channel numbers light.

Selecting the channel input source

Each channel on the C8X has a separate connector for the different input types. This means you can leave all your equipment connected to the inputs, or connect the C8X to a patch bay for easily connecting sources quickly.

Each input has separate connectors for Mic/Line inputs; the ISA inputs have instrument connectors on the front panel.

To change input source, both the ISA channels and channels 3 - 8 have an Input button. Press the Input button to cycle through the input sources. The indicators beneath the meters show the currently selected input source for each channel.

Pressing the Input button cycles between:

• ISA preamps:

  • Microphone

  • Instrument

  • Line-level

• Ultra-low-noise Focusrite mic preamps:

  • Microphone

  • Line-level

When you change input source, the preamp settings remain the same.

What preamp controls affect the C8X's line inputs?

The settings available for line inputs are slightly different to the other inputs on your C8X. When you set the input to Line the following input controls won't be available:

• Gain (the line inputs are fixed-gain inputs)

• 48V

• High-pass filter

• Auto Gain

• 430 Air/Air

• Impedance Ω

The preamp input gain controls how much signal you are sending into your computer and recording software.

It's essential to set a good level for the preamp input gain so you get the best quality recording. If the preamp input gain is too low, your signal will be too quiet and when you try to boost its level later you may hear noise in the recording; if the preamp input gain is too high you might 'clip' the input and hear harsh distortion in your recording.

Using the ISA preamps' input gain

Each ISA preamp has two gain controls. These work together to set the microphone or instrument gain. Stepped gain sets the main gain in 10dB increments; Fine gain lets you make 1dB adjustments.

Together, Stepped and Fine Gain provide a 79dB gain range.

Tip

You can use Fine gain on its own to set your gain. When Fine reaches maximum, Stepped gain increases.

For example, if Stepped is at 20dB and Fine is 9dB, turning Fine clockwise increases Stepped to 30dB and Fine resets to 0dB.

When you change ISA channels, both gain indicators show the stored gain for the newly selected channel.

Stepped Gain

Stepped Gain sets the gain level in eight steps across a 70dB range. After you select a channel, you can turn the Stepped Gain control to move through the eight positions (0dB, 10dB, 20dB, etc.). The LEDs around the encoder show the current gain value.

Once you've reached the set Stepped Gain to its maximum or minimum gain value, it won't increase or decrease the gain any further. You can fine tune the gain using the Fine Gain control.

Fine Gain

Fine Gain adds up to 9dB in ten smaller steps.

After you select a channel, you can turn the Fine control to move through its ten increments. The indicator around the control updates to show the setting.

When you reach the maximum Fine level, the Stepped gain increases. For example, if Stepped Gain is set to 40 and Fine Gain is set to 9, turning Fine Gain clockwise increases Stepped Gain to 50 and Fine Gain resets to 0.

Together, Stepped and Fine Gain provide a 79dB gain range.

Instrument input gain

When you set the input type to Instrument, both gain controls remain active and provide the same 79dB range as the microphone input. The gain value is consistent across Mic and Instrument modes.

Using preamps 3–8 Input Gain

To set the input gain for the standard channels (channels 3–8) use the select buttons to select the channel and move the Input Gain control.

The control's halo shows the current gain level. You can use the meter to set the correct level.

The gain changes in 1dB increments with a 69dB gain range.

Meters 1–8 show each C8X's input level.

As you increase the gain, or as the source gets louder the meters show more level coming into your computer.

To the meters' left, there's a scale from -48dBFS to 0dBFS. When you're recording aim for a signal level around -18dBFS, with the loudest parts of the signal reaching -12dBFS.

Press Input to cycle through the available sources. The LED shows which one is active:

You can only use one input type at a time per channel.

ISA preamp input source selection

Inputs 3–8 input source selection

You can change input source remotely from Focusrite Control 2 using the input source selector at the top of each channel strip.

The ISA inputs change between: Mic, Line, and Inst. Inputs 3–8 change between Mic and Line.

48V, also commonly referred to as 'Phantom Power', sends 48 Volts from your interface's XLR connector to devices needing power to work. The most common use is sending power to condenser microphones, but you may also need 48V for inline mic preamps, active dynamic microphones, and active DI boxes.

To turn on 48V:

The 48V icon lights to show it is enabled.

48V phantom power is now being sent to the selected XLR input and to any devices connected to the XLR input.

48V (Phantom Power) software control

To enable 48V (Phantom Power) from Focusrite Control 2 click the +48V button on the input you want to enable it for. This is the same as pressing the 48V button on the C8X's front panel.

+48V Phantom Power off

+48V Phantom Power on

Press the high-pass filter button to activate the 75Hz, 18dB/octave high-pass filter on the selected input.

Use it to reduce unwanted low frequencies, such as rumble from mic stands.

To enable the high-pass filter from Focusrite Control 2 click the high-pass filter button for the input you want to enable it on. This is the same as pressing the high-pass filter button on the C8X's front panel.

High-pass filter off

High-pass filter on

Auto Gain allows you to send a signal into your ISA C8X (for example singing or playing your instrument) for 10 seconds and let the ISA set a good level for your preamps. If you find the levels aren't right, you can adjust the gain controls manually to fine-tune the levels before recording.

To use Auto Gain:

If the Auto Gain was successful, the meter lights green before the C8X shows the gain value is shown. The gain is now set at a good level for your recording.

If Auto Gain fails, the meter lights red. Please see the section, The Gain Halo turned Red, for more information.

Auto Gain Software Control

To use Auto Gain in Focusrite Control 2:

1. Click the Auto Gain button in Focusrite Control 2.

2. Speak or sing into the microphone, or play your instrument during the Auto Gain countdown. Perform as you would while you're recording to make sure Auto Gain sets a good level.

   The Auto Gain process starts and the software Gain halo turns into a countdown timer.

If the Auto Gain was successful, the meter lights green before the C8X shows the gain value is shown. The gain is now set at a good level for your recording.

Auto Gain failed and the meter turned red

If the signal is unsuitable for Auto Gain (for example, there's no signal detected), after ten seconds, Auto Gain stops and the meters light red. The gain returns to the value you set before starting Auto Gain.

Auto Gain unsuccessful

This can happen for all unusable signals, including no signal, very quiet signals, and too loud signals. If you see this error message, try the following:

• Make sure you've connected the source to the correct input. 

• For condenser microphones, turn on 48V (phantom power).

• Ensure you're making sound while Auto Gain runs.

• Ensure the signal is not too loud. 

  • If you are using the XLR inputs for a line level device (synths, keyboards, amp modellers), use the jack inputs instead.

  • Reduce the connected device's output.

• If the signal is too quiet, increase the gain 25–50% before starting Auto Gain.

Multichannel Auto Gain

Auto Gain allows you to send a signal into your ISA C8X (for example singing or playing your instrument) for 10 seconds and let the ISA set a good level for your preamps. If you find the levels aren't right, you can adjust the gain controls manually to fine-tune the levels before recording.

You can use Auto Gain on as many channels as you like on your ISA C8X.

To use multichannel Auto Gain

1. Hold the Auto button for one second.

   When you're in multichannel Auto Gain mode, all the Select LEDs pulse.

2. Press the Select buttons for the channels you want to run Auto Gain for.

3. When you're ready, press Auto again to start the Auto Gain process on the selected channels.

Note

To cancel Auto Gain, press the Auto Gain button again at any time during the process. The gain returns to the value you set before starting Auto Gain.

Multichannel Auto Gain in Focusrite Control 2

You can also run multichannel Auto Gain from Focusrite Control 2.

To do this:

1. Open Focusrite Control 2 and go to the Inputs tab.

2. Click the dropdown arrow on the Auto Gain button.

3. Choose Auto Gain all or Auto Gain multiple….

   • Auto Gain all starts running Auto Gain for all your ISA C8X's channels.

   • Auto Gain multiple allows you to choose the channels you want to run Auto Gain for.

4. If you clicked Auto Gain multiple, tick the channels you want Auto Gain.

5. Click Start Auto Gain.

Once Auto Gain has finished, Focusrite Control 2 shows the channels and their new gain levels:

All Channels

Multiple Channels

Multichannel Auto Gain failed

Multichannel Auto Gain might fail during the process for one, multiple, or all channels.

If Auto Gain fails for all channels, you'll see the Auto Gain failed message.

If Auto Gain fails for one or some channels, you'll see the Auto Gain complete message, but with the option to Retry Auto Gain on all channels.

You can either:

• Click Retry and all Auto Gain runs again for all the channels you ran Auto Gain for, even the successful channels.

• Click close and run Auto Gain for any failed channels.

• Click close and manually adjust the gain for any failed channels.

430 Air is a modern recreation of ISA 430 MkII's Mic Air mode. It enhances the signal's high-frequency content, adding a sense of spaciousness, often referred to as “air”, to the sound. 430 Air uses an inductor-based circuit, which interacts with the preamp to deliver additional clarity, without the need for EQ.

To enable 430 Air from Focusrite Control 2 click the 430 button on the preamp channel strip. This is the same as pressing the 430 button on the C8X's front panel.

430 Air off

430 Air on

Press Insert to toggle the signal path through the Send/Return TRS connections for the selected ISA preamp. Use these to route the signal through outboard gear (e.g. compressors or EQs) before it reaches the ADCs.

To enable the channel's Insert point from Focusrite Control 2 click the Insert button at the bottom of the preamp channel strip. This is the same as pressing the Insert button on the C8X's front panel.

Insert point off

Insert point on

Press the impedance button labelled, Ω, to cycle through the four impedance values for the Mic input or two for the ISA Inst inputs. The ISA indicator LEDs show the selected setting. Different values affect the preamp’s gain and frequency response, as well as how connected microphones behave.

Line input impedance is fixed at 20kΩ and isn’t affected by the impedance Ω button.

To change the preamp impedance from Focusrite Control 2 click the impedance Ω button at the top of the preamp channel strip.

Different input types have different impedance available. Focusrite Control 2 greys out impedances unavailable for the currently selected input type.

When you enable the Console button, the ISA channels behave like they're part of an all-analogue signal flow. At lower levels the signal remains clean and transparent, but then you drive the channel harder (with higher-level input signals, or increasing the gain) you start to hear analogue saturation on the signal.

Console is a variable, all analogue effect and the result is warm saturation and low-end punch.

The Console effect uses a soft-clip circuit with variable control so you dial in the effect amount.

Variable Console mode

You can adjust Console mode and the effect applied to a channel. To enter Variable Console mode, hold the Console button for one second.

When Variable Console mode is active:

• The Console button and indicator LEDs begin pulsing blue.

• The ISA Fine value changes to blue.

The ISA Fine Gain now sets the Console effect amount.

If you change channel, the behaviour depends on the Console state for the new channel:

• If Console is on, Fine Gain stays in Variable Console mode and shows the Console amount for the new channel.

• If Console is off, Fine Gain goes back to controlling gain.

To exit Variable Console mode, press Console. If you enter Variable Console mode while Console is off, the channel activates Console automatically.

If channels are linked, adjusting the amount affects both channels together.

Note

The ISA Gain controls become temporarily unavailable in Variable Console mode.

In Focusrite Control 2 you can enable Console mode and adjust how much the Console has on the signal using a slider.

The Console button lights amber when it's on.

To adjust the Variable Console mode, click the drop-down arrow on the Console button and move the slider. Move it left for a more subtle effect and right to hear more saturation and low-end punch.

To enable Air, press the Air button. When you enable Air, this engages an analogue high-shelf circuit to subtly change the preamp’s frequency response to model classic transformer-based ISA mic preamps' impedance and resonance characteristics.

When you record with microphones this adds an enhanced clarity and definition in the mid-frequency range. Air is great to give an extra flavour on most sources, but works well on vocals and acoustic instruments.

To enable Drive, press the Drive button on your ISA C8X's front panel. Enabling Drive adds variable, DSP-based, harmonic distortion to emulate analogue preamp warmth.

Drive off.

Drive on.

In Focusrite Control 2 you can enable Drive mode and adjust how much effect Drive has on the signal using a slider.

The Drive button lights amber when it's on.

To adjust the Variable Drive mode, click the drop-down arrow on the Drive button and move the slider. Move it left for a more subtle effect and right to hear more distortion and warmth.

Linking channels lets you control two adjacent channels together as a pair, simplifying operation when you need matched settings for stereo sources or paired inputs.

Linking the ISA preamps

Linking preamps 3–8

Linking and unlinking preamps in Focusrite Control 2

To link preamps in Focusrite Control 2, click the linking button in the top-right corner of the inputs page . In the pop-up you can choose which inputs you'd like to link or unlink.

When you link two preamps, the link icon appears at the bottom of both channel strips.

When you unlink preamps:

• The first preamp of the previously linked pair becomes selected and lights amber.

• Gain levels and preamp settings stay the same, but you can now change them independently.

The Monitor control section relates to anything controlling your monitor outputs, including:

The Dim button reduces the output level being sent to your outputs by 18dB.

Dim off

Dim on

The Dim button is useful to help allow conversation or to try ideas in the room without stopping playback.

By default, Dim affects the Main monitor outputs 1 and 2, but in Focusrite Control 2 you can change this to control your Alt outputs.

Dim Software Control

To enable/disable Dim in Focusrite Control 2 click the Dim button in the Outputs section on the right.

The Dim button works in the same way as the Dim button on your C8X 's front panel and reduces the output level being sent to your outputs by 18dB.

Dim off.

Dim on.

The Mute button silences the signal being sent to your outputs.

Mute off.

Mute on.

By default, Mute affects the Main monitor outputs 1 and 2, but in Focusrite Control 2 you can change this to control your Alt outputs.

Mute Software Control

To enable/disable Mute in Focusrite Control 2 click the Mute button in the Outputs section on the right.

The Mute button works in the same way as the Mute button on your ISA C8X 's front panel.

Mute off.

Mute on.

The Mono button lets you sum a stereo monitor group to mono. While Mono is active, the C8X sums the left and right signals.

When you switch to another two output monitor group, the current mono state carries over.

Mono is only available when the current monitor group uses exactly two outputs. If the monitor group uses more outputs, the Mono button won't do anything.

Mono button off

Mono button on

Mono software control

To enable/disable Mono in Focusrite Control 2 click the Mono button in the Outputs section on the right.

The Mono button works in the same way as the Mono button on your ISA C8X's front panel.

Mono off.

Mono on.

Hold, or press, the Talk button to activate talkback. By default, talkback routes to the two headphone outputs.

If the Talkback button is unavailable, it may not be routed to any Mixes. See Talkback Software Control.

When you enable Talk, the other mix outputs dim, to make it easier to hear the talkback microphone.

You can change the talkback routing in Focusrite Control 2 to feed multiple mixes.

By default, the Talk button is ‘momentary’ – talkback is only active while you hold the button. You can change the Talkback button between momentary or latching from Focusrite Control 2. You can tell Talk is on if the button is lit.

Your C8X has a Monitor to adjust the level going to your monitor speakers. The Monitor control affects the three monitor groups, Main, Alt 1, and Alt 2, you can set up and edit in Focusrite Control 2.

Each monitor group lets you assign specific outputs to a setting and switch between different monitor setups at the touch of a button.

There are three options:

For example, your Main group could be a 5.1 surround sound system, Alt 1 could be only outputs 1-2 in stereo, and Alt 2 could be only output 3 to a centre-mono speaker for checking your mixes.

Your monitor group choices are stored and recalled with presets.

Assigning Outputs in Focusrite Control 2

You assign outputs to monitor groups in the Focusrite Control 2 Routing page. You can add up to all 12 analogue outputs to each monitor group, either as stereo pairs or as mono outputs. Each output can have its own source.

Any output you assign to one or more monitor groups is reserved for monitor use only. This prevents accidental routing to your speakers.

Any outputs you don't assign stay available in the Routing page as normal.

You can set the Level for each output individually to calibrate your system while in your listening position.

Note

You can't assign digital outputs, e.g. ADAT or S/PDIF to your monitor groups.

In this example there are three monitor groups: Main includes 12 physical Outputs, fed from 12 software Sources for a 7.1.4 immersive speaker setup, Alt 1 includes six outputs for a 5.1 surround sound speaker setup, Alt 2 is a stereo speaker setup. You can configure the Software Playback channels in your DAW's settings for the different listening formats.

In this example we're using the Main and Alt buttons to change the source for a single set of outputs: Main uses a stereo output from Software, Alt 1 uses Mix A, Alt 2 uses Mix B. Assigning mixes to the Alt buttons allows you to quickly change what's coming through your speakers. For example, a mix might include hardware inputs to allow us to direct monitor inputs alongside software playback.

Your ISA C8X has two headphone outputs. Both headphone outputs are independent from the analogue outputs. Each headphone output can have its own dedicated mix.

The headphone outputs are 6.35mm (¼”) TRS jacks. Many headphone have a 3.5mm TRS jack, to connect them to your ISA C8X you must use a TRS 6.35mm to 3.5mm adaptor.

The controls above the headphone outputs control the level going to your headphones.

Around the headphone controls are halo meters. These fill up clockwise, from blue to amber, to show the level going to your headphone outputs. The meters are pre-fade, meaning they are not affected by the headphone control setting.

The headphone output controls are encoders; you can control the level from the dial, or remotely from Focusrite Control 2.

Below the headphone controls are two Mute buttons to quickly mute the headphone outputs from the front panel.

The ultra-low-noise inputs, inputs 3–8, are switchable between microphone and line level.

You can leave the XLR and 6.35mm inputs connect and switch between them using the Input button on the front panel.

The ISA inputs, inputs one and two, are switchable between microphone, line, and instrument level.

Both ISA inputs have switchable insert path where you can connect outboard equipment using the line-level Send and Return 6.35mm jacks.

You can leave the XLR and 6.35mm inputs connect and switch between them using the Input button on the front panel.

ISA channel Send and Returns (Inserts)

The ISA channels have dedicated insert points with, balanced, Send and Return sockets for including inline external processors and outboard equipment (for example EQs, compressors, gates, multi-effects, or amp simulators) before the signal reaches the converters.

To use external processors with your ISA channels:

1. Connect the C8X's Send output to your external processors input.

2. Connect your processors output to the Return input on the C8X.

3. Press the Insert button to hear the effect.

The Send is taken after the Impedance setting, HPF, and 430 Air, but before Console. Send is always active.

To hear the Return signal, press the Insert button on the C8X's front panel, or in Focusrite Control 2.

Outboard tips

• Set the external processor’s input and output so the Return level closely matches the Send, and check the channel meters to avoid overload.

• While you can use time-based effects like delay and reverb, generally effects like this aren't used as inline processors and added in parallel to the original signal.

The Outputs labelled 1 and 2 can either be balanced 6.35mm (¼") jack or balanced XLR outputs.

Other than this, they are identical to Outputs 3–12.

Outputs 3 - 12 are 6.35mm (¼") TRS jack connectors.

You can use these outputs to send signal from your DAW to mixers or outboard equipment, or use them as extra monitor outputs.

To use the outputs with monitors, you can assign them to the Monitor control for surround sound and immersive sound applications, or use them in Alt Monitor groups. For more information see Assigning Outputs in Focusrite Control 2.