How to Add Inputs to Your Audio Interface with Carbon Pre

If you’ve ever found yourself needing more mic preamps and have available ADAT or Line input ports on your current audio interface, you're in the right place. We'll dive into what ADAT expansion is, how it works, and show you how a versatile mic preamp and expander like the Pro Tools | Carbon Pre can help you seamlessly expand audio interface’s available mic pres.

What is ADAT Expansion?

ADAT expansion refers to the process of increasing the number of available audio input and output channels on an audio interface or other digital audio devices by using the ADAT (Alesis Digital Audio Tape) protocol. This is typically done by connecting an external ADAT-compatible device, such as a mic preamp, converter, or expander, to your primary audio interface. The key benefits of ADAT expansion include increased flexibility and scalability for recording and mixing larger projects.

How ADAT Expansion Works

By using an ADAT-compatible audio interface, you can easily add more inputs and outputs to your setup. Here’s a closer look at how ADAT expansion functions:

• Digital Audio Transmission: ADAT uses optical cables (commonly TOSLINK) to transmit up to 8 channels of digital audio over a single optical cable.
• Connecting Devices: To expand your audio interface, you connect an ADAT-compatible expander to the ADAT input and/or output on your primary audio interface. This setup allows you to add additional preamps, inputs, or outputs to your existing system without needing a new audio interface.
• Synchronization: The devices involved need to be synchronized to ensure proper timing and data integrity. This is usually done via a word clock connection or using the ADAT signal itself for clocking.

How to Add inputs to your audio interface with Carbon Pre

Pro Tools Carbon | Pre is a versatile, high-fidelity mic preamp expansion that can integrate seamlessly with MTRX Studio, HD IO, or any other audio interface with available connectivity. It’s capable of expanding your audio interface's inputs by providing additional pristine mic preamps via ADAT, analog, or AVB connections. This guide will focus on expanding your audio setup with ADAT and analog connections, using MTRX Studio as an example:

1. Connect to your audio interface

Start by connecting the ADAT or analog outputs of the Carbon Pre to the ADAT or analog inputs of your interface.

• If you plan to run at higher sample rates such as 96k, connect two ADAT cables. One ADAT cable can transmit 4 channels at 96k, so connecting both will allow you to maintain a count of 8 preamps at this higher sample rate.
• If you plan on primarily running at a base sample rate (e.g., 44.1k or 48k), you can connect two Carbon Pres, one to each available ADAT port on your interface, to allow for 16 additional preamps.
• If you are connecting from the analog outputs of Carbon Pre, sample rate is not an issue for channel count—you can have 8 channels at all sample rates when going out the DA.

2. Connect the ethernet cable

Now, connect the Ethernet port from the Carbon Pre to your computer. This connection allows you to remotely configure the Carbon Pre's settings from Pro Tools or your control surface. Note that with this setup, the Ethernet cable does not transmit audio; it is only used for data transfer, enabling remote control and configuration.

3. Set up clocking

Since we are connecting two digital interfaces, we need to synchronize them to ensure proper timing and data integrity. There are two primary ways of doing this:

• ADAT Clocking: Connect an additional ADAT cable from MTRX Studio output to Carbon Pre input. Carbon Pre will always clock off of this ADAT connection when set up this way.
• Word Clock: Alternatively, you can take the Word clock out from your interface and connect it to Word clock in on Carbon Pre. (With this connection type, you will need to update the sample rate on the front panel of Carbon Pre manually).

4. Route your analog signal

In DADMan, route the incoming ADAT or analog signals to the desired DigiLink or Thunderbolt channels going to Pro Tools.

5. Tell Pro Tools to look at Carbon Pre

In Pro Tools, go to Peripherals – Mic Pre and select Carbon Pre from the drop down to enable control over the preamps. This step allows Pro Tools to recognize the Carbon Pre as an input source, enabling you to adjust preamp settings such as gain, phantom power, and more directly from within Pro Tools. 

6. Select the channels Carbon Pre is routed to

And lastly, go to Setup – IO– Mic Preamps and select the channels Carbon Pre is routed to. This step maps the inputs from the Carbon Pre to the appropriate channels in your Pro Tools session. By doing this, you ensure that the audio from the Carbon Pre is correctly routed, allowing you to record and monitor through the designated channels. This configuration is essential for proper signal flow and effective use of your expanded inputs

Now you’re record-ready

Now when you create a track assigned to one of these inputs, you can access all the Preamp controls directly from Pro Tools and any EUCON-enabled control surfaces (including the free Avid Control app).

This setup process is essentially the same for any interface with available ADAT or Line inputs. We happen to love the combination of a Pro Tools | Carbon Pre with a MTRX Studio because it gets you a few specific benefits including a solid immersive audio setup.