The Empirical Labs FATSO has now been in production for over twenty years, yet it still feels like something of an underdog in the Empirical Labs lineup. The Distressor gets most of the attention, thanks to its reputation for emulating a wide range of classic compressors, it’s become a staple in professional studios worldwide. The same can’t be said for the FATSO, which appears far less frequently by comparison. So why is that? Is it simply a case of people not fully understanding what the FATSO does or just how good it actually is?
I remember being immediately intrigued by the FATSO when I first came across it years ago, largely because of my deep fascination with analogue tape machines at the time. For those unfamiliar, FATSO stands for Full Analogue Tape Simulator and Optimizer. According to Empirical Labs themselves, it’s the coolest and most distinctive piece of hardware in their entire range, and it’s not hard to argue with that when you get to know the FATSO.
To really grasp what the FATSO is aiming to emulate, you first need to understand how analogue tape reacts to input levels. In the early days of tape recording, engineers would drive the tape with high levels in an effort to bury the noise floor beneath the signal. The side effect of hitting tape that hard was a natural compression of the signal, a gentle roll-off in the high frequencies, and a playback sound that felt noticeably ‘fatter’ than the original input. This character, warm, rounded, and slightly compressed, is exactly what many engineers felt was missing when the industry began shifting towards digital recording.
No doubt Dave Derr, the mastermind behind the FATSO, felt much the same. The early days of digital recording left many engineers grappling with the sterile, clinical sound of digital tape, (I recall my first ADAT leaving me feeling that way) and the FATSO was designed as a response to that. But to think of it as just a tool for replicating tape warmth would be missing the bigger picture. The FATSO is far more versatile than that, it’s capable of bringing weight, character, and cohesion to all sorts of sources in ways that go well beyond simply mimicking analogue tape.
The Empirical Labs FATSO offers a range of processing tools that give it its unique sonic character. Its Harmonic Generation and Soft Clipping circuit, built around a Class A design, gently rounds transients in a way that recalls the natural saturation of valves or analogue tape (more the later I think). The High Frequency Saturation, labelled WARMTH, is a dynamic low-pass filter that subtly tames excessive high-end build-up, softening harshness without dulling the signal.
Transformer and Tape Head Emulation adds low-frequency harmonic content, simulating the character of vintage input/output transformers and analogue tape machines. Rounding it out is the unit’s Classic Knee Compression, a smooth, musical compressor in the Empirical Labs style. It brings a natural levelling to instruments, vocals, or the stereo buss, striking a balance between sweet and punchy.
About 11 or 12 years ago, I was deep into recording an album of my own songs, a process that stretched out over a few years, with gear constantly coming and going. But the FATSO stayed with me the whole time, and for good reason. I absolutely loved what it did on the drum bus. Once the album was finished, I ended up selling off my entire studio setup, something I’ve regretted ever since.
The internals of the FATSO are rather complex, and the fear of it being copied is clearly evident as all IC chips have had their compnonent identification removed.
These days, I’ve moved to a mostly in-the-box mixing environment, and I really miss having the FATSO around. I’ve tried all sorts of ways to replicate what it brings to drums, but nothing has quite hit the mark. I did try the Universal Audio FATSO plugin back when I was using an Apollo interface, and while it wasn’t bad, it just didn’t have the same magic as the real hardware.
I’ve recently had the chance to spend some time with the new FATSO, and it’s completely reignited my love for the unit. It’s also reminded me just how much I miss having regular access to it, especially now, as I find myself deep in the process of mixing another album. The sound, the feel, the way it pulls things together, it’s still every bit as special as I remember.
It’s about the sound!
So what exactly did the FATSO do for drums? Well, it’s right there in the name, they just sounded fatter. More than that, the FATSO had a way of gluing the drum tracks together in a way that felt effortlessly musical. I used to drive the inputs hard, usually around 7 on the input dial. I’d set the compressor to BUSS mode, with the warmth at 2 and the TRANNY circuit engaged. That typically gave me around 3 to 6 dB of high-frequency compression and about 2 to 3 dB of overall gain reduction. The result was a drum sound that felt cohesive, punchy, and thick, without ever losing definition.
Of course, the FATSO isn’t just limited to drum duties, it also works brilliantly on vocals, bass, and guitars. It’s particularly effective on bass guitar, adding weight and control without killing the dynamics. The latest version of the FATSO has swapped out the original GR compressor setting for a new one called ELEVEN, which emulates the classic 1176. This update makes the unit even more versatile, especially in smaller studio setups where one piece of hardware needs to cover a lot of ground.
With a bit of clever tweaking, the FATSO can also be used for sibilance control on vocals. By combining the WARMTH control with the ELEVEN compressor setting, it’s possible to tame harsh top-end while still keeping the vocal sounding full and natural, giving the FATSO yet another role in the studio. And since it’s a stereo unit, you can even track two vocals at once with the same settings, applying compression and high-frequency smoothing across both channels. A very handy feature that adds to its versatility.
I’ve seen a few mastering rooms using the Empirical Labs FATSO, and I know of one in particular that relies on it during mastering sessions. They absolutely swear by it for certain mixes that, let’s just say, aren’t exactly in top shape. The FATSO’s ability to smooth out harshness, add weight, and bring cohesion can really help pull a problematic mix together in a musical and forgiving way.
Conclusion
If I had to choose just one piece of hardware for my studio, whether due to budget constraints or because I was working primarily in the box, it would be the Empirical Labs FATSO. What it does for drums alone makes it worth the investment in my book. That added weight, cohesion, and warmth is something I’ve never quite managed to replicate with software. If you’re in a similar position, searching for a touch of analogue character for your digital mixes or a versatile piece of gear that can handle multiple duties, do yourself a favour and beg, borrow, or at least audition a FATSO. You might just find it becomes the one box you can’t do without.
