It’s very simple – if you record music using Pro Tools with any regularity, and don’t require (or can’t afford) a full-blown HDX system, I cannot advise you strongly enough to buy Avid’s new Carbon interface. It has the two main features that I have been waiting for in a non-HDX system for the two-plus decades I’ve been using Pro Tools: near-zero latency monitoring through the DAW itself, and latency-compensated round-trip printing.

Most readers will likely understand the benefits of ultra low-latency monitoring immediately, since latency during tracking and overdubbing is something everyone has to jump through hoops to avoid, utilizing either an analog front end or one of the software solutions that interface manufacturers include with their hardware, such as Universal Audio’s Console or Metric Halo’s MIO Console. These applications allow you to tap into the audio that you’re recording before it hits Pro Tools, minimizing the delay between what’s being played live and what you’re hearing in the headphones. However, when it comes time for playback, you now need to listen post-Pro Tools, necessitating a completely new monitoring chain. This process of switching monitoring sources works alright for simple tracking, but during overdubs, especially when punching in, this double-pronged approach quickly falls apart. Carbon solves this problem handily by utilizing what Avid calls its “patented Hybrid Engine technology.” As opposed to a classic HDX system (without the Hybrid Engine) – where most audio processing is happening on an external DSP card, or an HD Native system – where all processing is happening directly on your computer’s CPU, the Hybrid Engine lets you determine on a track-by-track basis which “brain” is doing the “thinking.” I’ll explain more about this below.

The second above-mentioned game-changer may be less obvious, but I can’t tell you the number of sessions I have received to mix over the years that could have used this feature. The deal is, if you send a source from Pro Tools out into the real world, through, say, an outboard compressor or pedal chain, and record it back into the DAW, Carbon automatically aligns the processed signal with the original in a sample-accurate fashion, allowing for easy prints of phase-aligned parallel hardware processing. This is absolutely huge for those of us who love incorporating our analog gear into our mostly digital mix workflows, and not even something that most non-Avid HDX interfaces do properly! (My trusty old Lynx Aurora [Tape Op #73] system did; I miss that thing…).

I’m going to spare you the full description of the physical layout of Carbon. You can search for pictures and descriptions online to get an idea of the specifics of the I/O and how to control it via the two rotary encoders on the front of the unit. Basically, you get 25 inputs at 44.1 kHz and 48 kHz sampling rates (8 analog, 16 digital, plus the talkback mic). For the digital inputs, you get eight fewer at 88.2 kHz and 96 kHz, and twelve fewer at 176.4 kHz and 192 kHz, due to the antiquated and annoying ADAT protocol. For outputs, it’s 34 at the lower sample rates, since the stereo monitor outputs and the four stereo headphone outs (!) can all be accessed separately from within Pro Tools’ I/O Setup window.

Connection to the computer is over the AVB protocol, which uses the now ubiquitous RJ45 Ethernet jack. The Carbon interface shows up as a Core Audio device on a Mac, so it can be used for non-Pro Tools applications. There’s no Windows support yet, and for now, you can’t daisy-chain Carbon units, but there is a second jack for future expansion possibilities. Not all Ethernet adapters work for AVB; I had to purchase Apple’s Thunderbolt-to-Ethernet dongle to get Carbon to work with my Mac laptop even though I already had two different off-brand Ethernet adapters. Also, it does not work through a switch; it has to have a dedicated home run to the computer.

There just isn’t enough space here for me to get into the nitty-gritty about all that Carbon has to offer, so I’ll just quickly explain DSP Mode, and then give you my main pros and cons. (Spoiler alert: the pros outweigh the cons, big-time.) DSP Mode is a feature of the Hybrid Engine within Pro Tools (2020.11 and up) that unlocks when you use the Carbon as your main interface. It allows you, on a per-channel basis, to put tracks into a low-latency state while recording, via a little lightning bolt icon in the channel strip. Like, really low-latency, not just setting your buffer at the lowest setting and dealing with it. Like, under 1 ms latency at lower sample rates. In other words, Pro Tools HDX-levels of feeling, as if you’re monitoring through an analog recording device. In addition, you can add any plug-in that has a DSP version without introducing any discernible latency to your monitoring chain. Of the many plug-ins I use, only Metric Halo, Plugin Alliance, Softube, and Avid’s own formidable included plug-in suite can run in DSP Mode. Any native-only plug-ins (SoundToys, FabFilter, UAD, etc.) aren’t available to run in DSP Mode, either on the track itself or on any busses that the DSP-enabled track is feeding. These plug-ins can still run in your session, just not with DSP-level latency. That means that time-based native effects such as reverbs and delays can still be utilized while recording, they’ll just have a little extra delay time added to them. There’s a setting in Preferences to have all record-enabled tracks automatically enter DSP Mode, but sadly there’s no setting yet to have them automatically switch out of DSP Mode when you take them out of record.

Overall, from an audio standpoint, I’ve been extremely happy with all of the recordings I’ve done with Carbon. The mic preamps sounded good during my tests, and the converters and clocking have given me excellent results, both on the way in as well as during monitoring. You can even record at 32-bit, which I just discovered while sitting down to write this review, and I look forward to testing.

My main complaint about Carbon is that I have no love for ADAT as a digital protocol. In addition to the channel count limitations at higher sample rates, even “pro” Lightpipe/ADAT cables and connectors feel cheap and flimsy and don’t lock into place. On a mobile recording session I had numerous issues with the ADAT cables popping out. The time feels overdue for manufacturers to abandon ADAT in favor of more robust digital interconnectivity, like what you get with AES, MADI, or Dante. On the other hand, my 20-year-old Metric Halo 2882s [Tape Op #34] can feed them signal, which allows me to extend the life of those units within my new setup. Be aware that there are input latency differences between the analog and digital inputs on the Carbon, as on any interface with similar ports. If you split multiple mics on a single source between the analog and ADAT inputs, you will induce phase problems.

Another issue is that there are still several bugs to work out, whether they are in the current version of Pro Tools (2021.3.1 as of this writing), Carbon itself, or a combination of the two. I’ve had increased odd/glitchy Pro Tools behavior – including a few catastrophic crashes – since adopting the Carbon interface into my workflow. I’m sure between software and firmware updates, Avid will iron it all out, but be prepared for a little frustration here and there if you are an early adopter.

My last gripe is that Carbon has a bunch of features many of us don’t need. If you already have a substantial studio setup, you may well already have a talkback and cue system, monitor switching, enough preamps, etc. If not, you’ll appreciate the depth and style of those features with Carbon, but if so, you’re paying extra money for features you’ll rarely or never use. I would love a line-level “Pro” version with AES I/O and none of the “center section” features, and I think a lot of home and project studio owners would agree.

Yes, $4000 is a lot to spend on an interface when there are other devices for less money that appear to have most of the features of Carbon. However, once you take into account that a premium plug-in suite plus a year-long subscription to Pro Tools are included, the price tag does get easier to swallow. Also, the profound way in which Carbon has sped up my home studio workflow is worth every single penny, and it still costs way less than even the most affordable HDX solution.

Tape Op is a bi-monthly magazine devoted to the art of record making.

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