Eight-channel A-D/D-A ADAT Expander

Converters / Clocks

Published July 2024

Audio interface modders Black Lion Audio enter the world of ADAT expanders.

ADAT expanders add more I/O to compatible audio interfaces via an optical Lightpipe. There are lots to choose from, and the latest to jostle for our attention is Black Lion Audio’s Revolution EXP, a 1U rackmount device that offers eight analogue line‑level inputs and outputs (no mic preamps) and 24‑bit A‑D/D‑A conversion.

Its two pairs of ADAT ports support up to 96kHz operation for all eight channels in both directions, or four channels at 176.4 or 192 kHz. All the analogue connections are balanced TRS jacks on the rear, where I prefer them (when hooking these up to rack gear or a patchbay you’re not left with cables trailing from the front). Each input socket has a ‑10dBV switch. A pair of BNC connectors on the rear cater for word‑clock input and output. It’s also possible to have a clock embedded in the ADAT signal, so you don’t actually need a word‑clock cable, and if you have an interface that lacks word clock then this feature is particularly helpful. But word clock can be very useful, not least when synchronising multiple devices. Also, worth noting is that Black Lion have pedigree when it comes to building low‑jitter digital master clocks, and here they recommend using the word‑clock connection where possible as it can often deliver more reliable sync.

Finally, a USB‑C socket (reserved for firmware updates) is joined by a DC power inlet for the supplied switch‑mode supply, a lightweight wall‑wart type. I’d have preferred a locking connection of some sort, and ideally a PSU that terminated in an IEC socket for convenient connection to my rack PSU. But on the plus side, the external PSU keeps mains AC well away from the audio circuitry, and external supplies are easy to replace if ever they fail.

The Revolution EXP includes both word‑clock in and out as well as dual ADAT ports supporting S/MUX operation up to 192kHz for four channels, and a maximum of 96kHz for all eight channels.

In terms of build quality more generally, the case is robust and nicely finished; flawless. The controls and meters couldn’t be easier to use either. On the front, every input and output channel has its own eight‑segment LED level meter, with input channels 1‑4 and 5‑8 in clusters to the left and output channels 1‑4 and 5‑8 to the right. It doesn’t offer as fine resolution as, say, the meters on my Ferrofish A32’s screen, but it’s a large, clear, no‑nonsense display. Plenty good enough to make the right judgements.

A push‑turn encoder toggles the clock source and sample rate, while a minimalist screen and a few LEDs display the current status clearly. One more LED flashes red when sync’ing over a word‑clock connection, settling to green when sync is established. While this doesn’t occur for ADAT‑only sync, that’s by design — more on that below. Finally, the front panel on/off rocker switch — a feature all devices really should have today.

What this boils down to is a device that’s intuitive to operate. What you see is what you get, and a quick glance tells you almost everything you need to know.

Impressions

To test the Revolution EXP I hooked it up to a couple of ADAT interfaces: a Ferrofish A32 converter (in turn connected to an RME MADIFace USB using optical MADI), which has both ADAT and word‑clock connectivity; and an Avid MBox Studio, which supports ADAT but lacks word-clock support.

Setting the Revolution’s clock source to Macro‑MMC (its internal clock), the Ferrofish to sync to the ADAT signal and the RME to sync to the Ferrofish’s MADI clock, everything worked as expected — I could route sound from the Revolution EXP to my DAW and vice versa. With the same setup, I could slave the Revolution EXP to the Ferrofish. If setting the RME or Ferrofish as the clock master, though, while word‑clock sync was fine, I was unable to get the BLA unit to sync to the ADAT clock. To check if it was an issue with the BLA unit or my setup, I tried it with the MBox Studio, and happily the Revolution EXP sync’ed flawlessly over ADAT. Repeating the test with another device again revealed no problems.

I mentioned that when sync’ing via ADAT, you don’t get the sync light to confirm that sync is in progress/established. BLA say they didn’t want people to rely on an LED, as they’ve learned over years of modding interfaces that ‘multiples’ often sync but sub‑optimally: a device set to 44.1kHz will line up on every other sample with another set to 88.2kHz sufficiently well to pass audio and show sync. So they prefer you to listen. This confused me at first, because the Ferrofish setup wasn’t sync’ing over ADAT and I had no visual cue about the problem. But in general their approach makes sense.

BLA make it very clear that their aim is not simply to improve on‑paper specs, but to judge the best configurations through painstaking listening tests.

As with BLA’s audio interfaces, the main selling point in the company’s literature is the sound. BLA’s roots lie in modifying converters and audio interfaces to improve the analogue stages, through tweaks of the sort Sam Inglis described when he reviewed their Revolution 2x2 interface. The technical specs are published on BLA’s site, but BLA make it very clear that their aim is not simply to improve on‑paper specs, but to judge the best configurations through painstaking listening tests. Consequently, they’re keen to point out that they could have ‘bettered’ some specifications through different component choices but this would have sounded less good than what they settled on. For example, the dynamic range figures (112.837dB for the inputs, 110.175dB for the outputs) could be made more impressive, because they selected some components with a slightly higher noise floor than alternatives that, by implication, they felt compromised the subjective sound quality.

The sample rate and clock sync are easily set without any menu‑diving required.

Clocking Off

With all that in mind, how does the Revolution EXP compare with other ADAT expanders? Well, it certainly sounds very good to me — a touch better than my Ferrofish A32 when listening critically over headphones (though it’s hard to set up tests where the act of switching can’t influence your judgement). Subjectively, I’d describe it as very clean, with a nice, extended top end. It’s clearly very good.

Another factor one might judge an ADAT expander on is the feature set. Some might consider the Revolution EXP to be a little light in this respect: my Focusrite Clarett+ OctoPre, for example, not only has eight mic preamps but also caters for line and instrument signals, as well as offering the Air processing option and insert points, and it’s not dissimilar in price. Another alternative is the Ferrofish Pulse 16, which provides twice the line‑level I/O count with full S/MUX support and allows you to adjust the input gain and output level for each analogue channel to boot. In short, the competition is fierce, and inevitably for a US‑made device, the price is a little more accessible in the US than the UK, while it’s the other way around for European companies’ devices like the Ferrofish.

But for all that, I love the simplicity and no‑nonsense approach of BLA’s Revolution EXP. Do you want more line‑level I/O to hook up some outboard to your DAW? Here it is. It’s high quality, well built, sounds great and is very easy to operate — and there’s an awful lot to be said for that!