In this article for Production Expert, Mastering Engineer Mike Thorne put the RME ADI-2 FS to the test to see if this is the sound card for mastering?

When it comes to working from home studios, many of us don’t have access to really high-end AD/DA conversion. We often use something decent that “gets the job done” but it can be difficult to justify the outlay on getting that final few per cent of quality (remember: profit is what you don’t spend).

RME’s very reasonably priced AD/DA, the ADI-2 FS (catchy), offers an interesting alternative to the expense and hassle of upgrading your current interface: Keep your current setup (and investment) but upgrade the all-important AD/DA stage and clock source.

Imagine using your “old reliable” interface, with all of the interconnects and workflow you’ve invested in, but given a new lease of life with “mastering-grade” conversion and a high-end master clock. Interested?

Why Should You Care About AD/DA Conversion?

Before we get into the details of the RME, let’s take a quick detour and look at why the quality of AD/DA conversion matters.

The simple and obvious answer is that everything you record and everything you hear passes through your analogue to digital and digital to analogue (AD/DA) converters. The quality of converters you use affects every decision you make when working on audio. It has to: You’re literally hearing the converters when you listen to any digital audio.

The extent to which this matters in the real world has been discussed ad infinitum. Once you get beyond a certain level of quality, it really is just about your preference - some of us like the colour yellow, some of us prefer orange. Here are a few things that matter to me in a converter:

• On the DA side, when used for monitoring, I don’t want the converter to add any “colour” to the audio - I just want something that has loads of headroom and that accurately presents the source audio. This helps me work quickly, keeping perspective and without second-guessing what I’m hearing.

• On the AD side, when capturing a performance or printing a master, I don’t always want conversion that is clinically transparent. Perhaps influenced by my years of using analogue tape and valve consoles, I’ve enjoyed using Burl converters for more than 10 years - these have a transformer on each input so you can subtly alter the harmonic content by how hard you drive them.

• However, when looping back to use the analogue gear as an insert, I would prefer an AD stage that is transparent so it’s not adding an additional layer of “vibe”.

I’ll admit that all of this gets very “inside baseball”, very quickly. Suffice to say that if you’re wondering about whether your audio interface is in need of an upgrade, RME has now given you a genuine alternative to having to change your entire system.

RME ADI-2 FS vs. Super High-end Audio Gear - How Does It Compare?

Let’s be honest: How many of us read the manual in-depth before hooking up a piece of new gear and playing with it? Me neither. The RME passes this test with flying colours. Although it does have some nice tricks up its sleeve for which you’ll need to refer to the manual (see the tech section below), basic use as an AD/DA was easy to set up on my system.

How does the RME sound? Well, unless you’re in the room, it’s very difficult to describe or even demonstrate the “sound” of an audio interface because even with audio examples, you won’t be hearing the DA section. But I’ll try.

For context, my usual mastering setup is Pro Tools HDX, with Burl and Avid converters and the analogue monitoring section on an SSL AWS 900+. To integrate the RME into my system I used the ADAT optical connectors on my Avid Omni. This worked reliably. Latency wasn’t a consideration as I was using the RME on mastering sessions, rather than recording sessions.

Used as my stereo monitoring DA, I loved the sound of the RME - it was enjoyable to work with. Over a longish (10 hour) day and with deadlines looming, I appreciated that it wasn’t tiring to listen to - it only sounded harsh if the source material sounded harsh. It didn’t take away or add anything strange to the low end. The midrange, although slightly more forward than the Burl, was something I quickly got used to and was fine.

I noticed very slightly reduced headroom compared to the Burl. But that’s really nitpicking and wouldn’t be an issue in day-to-day use. For context, the Burl has an external massive 300W continuous power supply so it’s not really a fair comparison (The RME’s headroom is up to +19 dBu vs. the Burl’s +22 dBu)

I got to hear the AD side when using the RME as a stereo loopback converter to insert some valve gear into my mastering chain. Again the RME was excellent in that I didn’t notice anything lacking or being added in the round trip. At this stage in the processing chain, I wasn’t hitting anything too hard, level-wise, but I didn’t have any issues with headroom.

The unexpected bonus feature: Like a lot of mastering engineers, I spend a large part of the day on headphones, checking for bad edits, clicks, pops, hums etc, both in the source material and when QC’ing the production masters. For a while, I’ve had the pleasure of using a Chord Electronics DAC and headphone amp to drive my HEDDphones. The HEDDs use an air motion transformer (basically a ribbon driver, rather than a voicecoil), the point being they need loads of power to drive them properly. This is another area where the RME stood up. Although not quite up to the Chord amp (a unit that costs nearly 7 times the RME) the headphone amp on the RME was very good and I could absolutely use it without any issues. I missed the crossfeed option on the Chord but was easily able to recreate this with the Goodhertz CanOpener plugin. Worth noting is that the “Pro Model” (RME ADI-2 Pro FS R) does have a crossfeed feature built-in.

Build Quality And Controls

Mention RME to an audio engineer and you'll likely hear phrases like "professional", "reliable", “accurate" and "reasonably priced”. I have several colleagues that specialise in classical location recording who wouldn’t turn up to a session without their beloved RME gear.

I can confirm that the build quality of the ADI-2 FS unit I received lives up to RME’s reputation. It feels reassuringly weighty and nothing rattled (you’d be surprised!).

On the front panel, the metering is clear, the buttons are solid and the analogue output volume pot is smooth, with no discernible jumps in level.

All the standard controls you’d expect in an AD/DA converter are present. You can select various analogue input levels, from +4 dBu through to +19 dBU and you can independently set the analogue output levels also between +4 dBu and +19 dBu.

You can choose sample rates between 32 kHz and 192 kHz and the RME SteadyClock (see below) will function as master or slave.

You can also bypass the AD converter and use the unit in digital “loop-through” mode. This turns the RME into a digital format converter and distributor. Similarly, the DA converter can be bypassed and the analogue “loop-through” allows you to use the RME as an analogue impedance converter or to balance unbalanced signals (or vice versa). It’s definitely worth digging into the manual for this. Check out the signal flow diagram on this page for details.

On the rear panel, there is no play whatsoever in any of the connectors, living up to RME’s “Made in Germany” credentials. Attention to detail here is obvious - the included external PSU has a power jack with a locking plug that even has an LED on it - super helpful if you’re on location trying to fault find.

Technical Specification

It’s probably clear by now that I’m not a “technical” audio engineer although I’d love to be. Instead, I’m a musician/audio engineer so I can quickly get out of my depth when the conversation moves to technical and theoretical details. With that disclaimer, here are the main tech points:

Analogue inputs: XLR and TRS line-level (via Neutrik combo connectors), servo-balanced design that handles balanced and unbalanced signals correctly. The maximum input level is +19 dBu.

Analogue outputs: 2 balanced line-level outputs on XLRs. 2 unbalanced line-level outputs on separate TRS connectors. The maximum output level on both connecters is +19 dBu.

Digital I/O: Coaxial and optical connections. The RME will automatically detect AES, SPDIF or ADAT formats, although to use AES, you’ll need to make up a simple adapter (details in the manual). Both coaxial and optical connections will accept sample rates between 32 kHz and 192 kHz, 24 bit. To use ADAT formats above 48 kHz the RME uses Sample Multiplexing (S/MUX) to enable sample rates up to 192 kHz.

Headphone amp: Very low impedance (0.1 Ohms) and headroom up to +19 dBu (6.9 Vrms) maximum output. Check out this link for more info on RME’s headphone section:

Clock: The ADI-2 FS uses RMEs top-end SteadClock FS. Aside from telling you that the FS stands for femtoseconds I’m gonna leave this to RME to explain:

Conclusion

We’ve touched on why converters are important and the law of diminishing returns when you’re trying to get the last 1% of quality.

This is where I think the ADI-2 FS can really help. If you have an audio interface that has the functions you need and supports your workflow, not having to throw all that away when upgrading the converters is a great choice to have, especially at the price point of the RME.

Will I be buying the ADI-2 FS? For recording? Probably not. I’m too entrenched in the Avid HDX world for low and consistent latency during tracking and my Burls play nicely with Pro Tools delay compensation when mixing. But for mastering? I loved the RME. It was genuinely useful to have a different flavour of AD, in addition to the Burl and the quality is very good. Hopefully, they’ll forget they’ve lent it to me. Although probably not!

For full details on the RME ADI-2 FS, head to Synthax Audio UK’s website.