Using the Clarett⁺ Octopre

All eight analogue inputs use “Combo XLR” connectors. These accept male XLR connectors, TS (unbalanced) ¼” jacks or TRS (balanced) ¼” jacks.

When you use an XLR connector, the preamp automatically configures gain and impedance to receive microphone level signals. If using a ¼” plug, the preamp accepts balanced or unbalanced line level signals. When you enable INST mode (Channels 1 or 2), the 1/4” input is optimised for an unbalanced, high impedance signal.

You can connect the line outputs of the Clarett⁺ Octopre to the analogue line inputs of outboard equipment (or any other device), to use it either as an analogue, 8-channel microphone preamplifier, or as an analogue “break-out box” for ADAT signals when in ADAT>LINE mode.

The outputs are balanced; see [20] on for the pinout. Ready-made DB25-to-XLR or DB25-to-jack breakout cables are available from professional audio suppliers.

Use the OPTICAL OUT ADAT port(s) [18] to connect the Clarett⁺ Octopre to the ADAT input(s) of an audio device using TOSLINK optical cable(s).

The ports can send eight channels of audio at 44.1 kHz or 48 kHz sample rate via a single optical cable. At these sample rates, the two ports carry the same eight channels.

At 88.2 kHz or 96 kHz sample rates, each port sends four channels. The right-hand port carries Channels 1 to 4, the left-hand port carries Channels 5 to 8; you need two TOSLINK cables to send all eight channels.

At 176.4 kHz or 192 kHz sample rates, each port can transmit two channels. The right-hand port carries Channels 1 and 2, the left-hand port carries Channels 3 and 4. The OctoPre is restricted to four channels of digital audio at these sample rates; the outputs of Channels 5 to 8 are not available via the ADAT ports.

Use the SAMPLE RATE switch [9] to select the sample rate frequency. It is essential the sample rate selected on the Clarett⁺ Octopre matches the sample rate set on the receiving digital device.

Two synchronisation options are available:

Clarett⁺ Octopre as clock leader:

Connect the OctoPre to the receiving device via the OPTICAL OUT port(s) and ensure the receiving device is set to source its clock from its ADAT input (and the sample rates on both devices match).

On the OctoPre, SYNC should be set to INTERNAL and the LED will illuminate.

An alternative method is to synchronise the receiving device to the Clarett⁺ Octopre’s WORD CLOCK OUT using a BNC cable. The receiving device’s sync source will need to be set to its external word clock input.

Clarett⁺ Octopre as clock follower:

Connect the OctoPre to your interface via the OPTICAL OUT port(s) and connect a BNC cable from the digital system’s word clock leader to the OctoPre’s WORD CLOCK IN connector (also ensuring the sample rates on all devices match).

On the OctoPre, SYNC should be set to W/CLOCK and the LED will illuminate.

Use the OPTICAL IN ADAT port(s) [19] if you need to convert digital audio (e.g., the output of a DAW) to analogue, using the Clarett⁺ Octopre’s ADAT > LINE mode.

The right-hand port can receive eight channels of audio at 44.1 kHz or 48 kHz sample rate via a single optical cable.

At 88.2 kHz or 96 kHz sample rates, each port can receive four channels of audio. The right-hand port carries Channels 1 to 4, the left-hand port carries Channels 5 to 8; you need two TOSLINK cables to receive all eight channels.

At 176.4 kHz or 192 kHz sample rates, each port can receive two channels of audio. The right-hand port carries Channels 1 and 2, the left-hand port carries Channels 3 and 4. The OctoPre is restricted to four channels of digital audio at these sample rates.

Use the SAMPLE RATE switch [9] to select the desired frequency. It is essential the sample rate selected on the Clarett⁺ Octopre matches the sample rate set on the transmitting digital device.

An important feature of all models in the Clarett+ range is the analogue preamplifier design. The circuitry includes an AIR function, individually selectable on each channel. AIR subtly changes the preamp’s frequency response to model the impedance and resonance characteristics of Focusrite’s classic transformer-based ISA mic preamps. When recording with microphones, you will notice an enhanced clarity and definition in the mid frequency range, just where it is most needed for vocals and many acoustic instruments.

Each preamplifier channel includes a switchable insert point to connect external processing equipment such as compressors or noise gates. The insert includes a send and a return: with no jack in the INSERT socket, the channel signal path is uninterrupted. The insert send and return are both unbalanced. Use a TRS jack wired with the tip (send) and ring (return) of the jack wired to two separate cables; such cables (often referred to as ‘Y-cables”) are available from professional audio suppliers.

The insert point is post the AIR circuitry (external equipment will receive a signal modified by AIR) and post the front panel GAIN controls [4]. When using an insert point, try to adjust the input and output levels of the external processor so the return signal is about the same level as the send. If the external processor has too much gain, you run the risk of overload within the OctoPre, so use the channel meters [7] to check the return signal level.

Use the front panel INSERT/AIR buttons [6] to enable the insert point. (First select INSERT using the main switch [8].) The channel LED will illuminate green to confirm selection.

Selecting ADAT>LINE mode ([12] on the front panel) reassigns the eight sources feeding the analogue LINE OUTPUTS D-sub connector [20].

This mode allows you to use the Clarett⁺ Octopre to connect an 8-channel ADAT format output (from a DAW, for example) to a set of analogue inputs. For example, you can send the channels from your DAW to outboard equipment to use as part of your mixing process.

When ADAT>LINE mode is enabled, the eight Clarett microphone preamplifiers are still operational, and their outputs remain available at the OPTICAL OUT ports.