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McDSP Moo X & APB-8

Hybrid Processing System By Sam Inglis
Published July 2020

McDSP Moo X & APB-8

McDSP's software-configured analogue processing system now has new hardware and software options — and support for more DAWs.

Engineers are often forced to trade off quality against convenience. Convenience usually wins in the end, and when it does, we tend to look for ways to rationalise it. Mixing 'in the box' is a classic case in point. The practical advantages of instant recall and go-anywhere portability are obvious — and as plug‑ins get better and better, any sonic advantage that analogue outboard has gets narrower and narrower. Or so we tell ourselves

Speaking for myself, I've been mixing 'in the box' forever, and if I'm honest, had stopped wondering whether it might not be perfect. If I couldn't always make crushed room mics sound good, or I had to laboriously automate fader moves to make vocals sit in the mix, I took that as a reflection on my own limited abilities rather than any inherent problem with plug‑in compression. Then, last year, I tried McDSP's APB‑16 — you can find my review online at — and I changed my mind.

A Better Box

There have been many attempts to introduce digital convenience to analogue processing. For instance, there are analogue compressors and equalisers with digitally controllable parameters, and sometimes these can even be manipulated through a plug‑in interface in your DAW. However, the Analog Processing Box takes the concept much, much further. Behind its none-more-green 1U front panel there lurks an array of what McDSP call programmable analogue circuitry: gain-reduction and saturation components that can be configured remotely using digital control. This circuitry sits between high-quality D‑A and A‑D converters, and is topped off with a Thunderbolt connection that pipes audio directly in and out of an Apple Mac computer.

So, in comparison with conventional analogue hardware, you lose the tactile experience of working with physical knobs and buttons, and you lose the option of tracking through compression in the normal way. But you also lose the headaches associated with patchbay wiring, level calibration and latency compensation. And, more importantly, there are huge gains. From a usability point of view, the APB processing is no different from a conventional suite of plug‑ins. Simply saving a project in your DAW is enough to save all APB parameters, meaning full recall is guaranteed. And not only are APB parameters controlled from plug‑in windows, but they can be automated in the standard way too. The APB doesn't tie up any of your audio interface's I/O, or impact on the 32-channel limit that Pro Tools users love to complain about.

Better still, the programmability of the APB makes it far more versatile and powerful than any traditional analogue outboard unit. Depending on how those internal components are arranged, it can adopt a wide variety of compression characteristics, from valve and opto-like gooiness, through fast and hard SSL-style 'mix glue' to full-on pumping. And the number 16 in the model name is no accident: an APB‑16 offers no fewer than 16 mono (or eight stereo) channels' worth of analogue compression, each independently configurable using an instantly familiar plug‑in interface.

The Better Half

Compared with a native plug‑in suite or a DSP co-processing box, the APB‑16 is undeniably expensive. However, the experience of using it quickly convinced me that such a comparison is the wrong one to draw, because it sounds like no digital compressor I've heard. Change your parameters and compare a single APB‑16 with an outboard rack containing 16 channels of top-quality analogue compression, plus all the apparatus needed to integrate that into your DAW, and it's not expensive at all. In fact, it could represent better value for money than almost anything else in your studio.

Outwardly, the new APB‑8 hardware appears identical to the APB‑16, the only difference being the number of processing channels available.Outwardly, the new APB‑8 hardware appears identical to the APB‑16, the only difference being the number of processing channels available. The APB units connect to your Mac via Thunderbolt, but also need to be sync'ed with your audio interface using word clock (or both sync'ed using a master clock).The APB units connect to your Mac via Thunderbolt, but also need to be sync'ed with your audio interface using word clock (or both sync'ed using a master clock).

The fact remains, though, that you can only access that value for money if you have the money, and the APB‑16's price tag puts it out of the reach of many. Comparing APB to conventional outboard also raises the question of whether 16 channels' worth of premium analogue compression might not be a bit of a luxury; even the most devoted advocates of hybrid mixing would be lucky to have 16 rackmount compressors on tap in their control rooms. So the new APB‑8 makes perfect sense.

It is, in every respect apart from channel count, identical to the APB‑16. It's the same size and shape, every bit as green, sounds exactly the same, and likewise requires only a Thunderbolt connection to the computer and a word-clock feed from your audio interface. (Like the APB‑16, it comes with a word-clock cable but not a Thunderbolt cable.) The only differences are, first, that it is limited to eight mono or four stereo channels of APB processing, and second, that the price looks a lot more attractive to the penurious project-studio owner. And you needn't worry about the channel count being limiting in the long run, because the APB concept is inherently scalable, allowing you to add further APB‑16 and APB‑8 units at any time — up to five in total can be connected in any combination.

The APB concept is inherently scalable, allowing you to add further APB‑16 and APB‑8 units at any time.

On The Move

If this was just a review of the APB‑8, it would therefore be very short, but the review unit arrived in time for me to test two new APB features. At its launch, the APB‑16 was only compatible with Pro Tools, and only with Apple computers. It's still Mac-only, but you can now use it with pretty much any DAW courtesy of VST and Audio Units support. Officially, only Logic and Cubase are qualified at the time of writing, but I had no problem running the APB‑8 plug‑ins in PreSonus Studio One, which is compatible with both standards. Functionally, VST and AU versions appear to be absolutely identical to the AAX ones. As before, the only real restriction compared with conventional plug‑ins is that any bounces or renders have to be done in real time — just as with any outboard processor.

The other new feature is less utilitarian and more sexy. Moo X was announced back at last year's AES Convention, but has only just become available. Like the other APB plug‑ins, it's included as standard with the hardware, though it needs to be separately authorised to an iLok account. Apparently a play on 'mu', McDSP use the name Moo for a number of their offerings which emulate valve-based circuitry, and Moo X draws its inspiration from '50s valve mixing consoles by the likes of RCA. However, there aren't any actual valves in the APB hardware: the Moo processors emulate the same behaviour using solid-state circuits.

Functionally, Moo X adopts the same paradigm as existing products such as Slate Digital's VCC, Waves' NLS and Softube's Console 1, meaning that although it's a mixer emulation, it doesn't actually mix audio. The idea is that you have a number of separate instances on individual channels or busses, plus an optional 'master' instance. The individual channel Moo X plug‑ins have only the controls relating to that channel, while the master instance displays a full mixer window with controls for all the individual channels. These are, in effect, remotely controlling the individual channel instances: the actual routing and summing of audio is still being handled in the background by your DAW.

McDSP describe Moo X as a "hybrid mixer", and that's because the channel plug‑in combines analogue saturation and compression with digital EQ. The latter is intentionally very simple, providing the sort of basic tone-shaping you'd expect from a '50s mixing console: broad treble and bass bands, with continuously variable frequency controls and up to ±12dB boost or attenuation. The EQ can be placed pre or post the analogue element of the processing, which is governed by just three controls: saturation, compression amount and 'TC', which jointly varies both the attack and release times. A VU meter and an output fader are augmented by solo, mute and polarity switches.

Each instance of the Moo X channel plug‑in can be assigned a number, and thereafter controlled from the relevant channel on the 'master' mixer.Each instance of the Moo X channel plug‑in can be assigned a number, and thereafter controlled from the relevant channel on the 'master' mixer.The VU meters can be switched to display either output level or gain reduction, but there's no visual indication of this setting apart from the actual behaviour of the needle. It's clear enough when the transport is stopped, but less so when compression is happening, so it might be helpful if the background changed colour when you click to engage gain-reduction mode.

Each individual instance of the Moo X channel plug‑in can be assigned a number, and appears in the corresponding slot on the 'master' Moo X Mixer plug‑in. You can then conveniently adjust all the individual channels' controls from one place. The Moo X Mixer plug‑in doesn't include EQ for the bus or channel it's on, but has a somewhat more flexible master bus compressor with separate Threshold, Attack and Release controls. Moo X can't automatically pick up channel names or numbers in the way that Console 1 can, but this won't be a problem in real terms unless you are lucky enough to have several APB‑16s and want to run a huge mix. Channels within the Moo X Mixer plug‑in are viewed in two banks of eight, and a virtual scribble strip at the bottom lets you name them manually if you wish.

Each Moo X channel takes up one APB processing 'slot', so on an APB‑8, you can have a stereo Moo X Mixer as your master along with six mono or three stereo channel instances. At the other end of the spectrum, a single Moo X mixer can span multiple APB units; the limit is currently 16 stereo channels per Moo X.

Incidentally, one neat feature I've not seen before is that if you bypass a single instance of Moo X in the Pro Tools mixer, all the other instances are simultaneously bypassed. This makes it trivial to do A/B comparisons, as long as the output fader in the Mixer instance is set appropriately.

Moo Music

In use, I found I didn't often employ the saturation on the individual channels. A little of this goes a long way, and if you crank it to the top you can find yourself in full-on 'Revolution' territory. If warmth rather than outright grit is what you're after, it's easier to achieve by turning up the make-up gain on the Moo X Mixer's bus compressor — and it sounds rather fab when you do.

The channel EQ also takes a little bit of getting used to if your reference is anaemic plug‑in equalisers, because a couple of dB makes a serious difference to the sound. Once you get into the swing of things, though, you quickly learn how to balance channel EQ and compression settings to shape both the tone and dynamic response of the source, in exactly the way that one might do with analogue outboard. The limited control set on the channel compressor is much more of a blessing than a curse, allowing you to very quickly dial in settings that just work. On many sources, the default time constants do the job admirably; if they don't, the TC dial runs all the way from snappy to sloppy, and sounds great throughout.

Even on an APB‑8, Moo X gives you the resources to transform a drum kit recording. Place mono instances on the kick and snare, stereo channels on the overheads and room mics, and a Moo X Mixer across the drum bus, and if two minutes' work with the Compression knobs doesn't bring a smile to your face, you're in the wrong job. In particular, you can absolutely smash a room mic without it sounding lifeless, or jerky, or bringing up all those unpleasant mid-range components in the way that plug‑in compressors usually do. Nor is it only useful on drums, and if you decide that the vocals, bass and electric guitars should share in the love, they'll certainly love you back. Very shortly after this you might find yourself wondering what you can sell in order to add another APB to your system!

In other words, Moo X sounds great, and is yet another demonstration of the worth of the APB concept. The APB was already a very powerful and versatile wolf of an outboard rack in plug‑in sheep's clothing; Moo X integrates all that power into a single framework, with benefits that are both audible and ergonomic. On an APB‑8 you'll have to pick and choose fairly carefully which channels should receive those benefits, but whether you take this route or simply treat it as eight top-class compressors in a single 1U rack, it offers more than enough power to make a real difference to any mix. Revisiting the APB has only strengthened my view that it's a concept whose time has come. It shows that with enough ingenuity on the part of manufacturers, there needn't be a compromise between quality and convenience. We can have both!


  • APB‑8 offers a more affordable, yet still very powerful, way to access McDSP's analogue plug‑in technology.
  • Moo X sounds great and is very easy to use.
  • VST and AU support mean any Mac owner with a Thunderbolt socket can join in the party.


  • Metering in Moo X could be clearer.


McDSP's APB system integrates analogue processing into 'in the box' mixing as never before. The APB units are more versatile and more convenient than conventional outboard, but they don't compromise on sound quality.


£3999 including VAT.

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