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Mäag Audio Magnum-K

Analogue Compressor & EQ By Bob Thomas
Published June 2017

Mäag Audio Magnum-K

With dual compressor stages and dual-band, boost-only EQ, the novel Magnum-K shows that high-end outboard needn’t be retro.

Many of today’s new hardware processors are emulations and/or recreations of a relatively narrow range of iconic, vintage mic preamps, EQs and compressors. Thankfully, though, there are still some very talented designers out there who bring different ideas to market. One such designer is Cliff Mäag Senior, a highly respected and experienced studio recording engineer who also has a background in audio hardware development at NTI and Nightpro — he designed the latter’s PreQ3 and EQ3D, with the then-novel ‘Air Band’ concept, in the early 1990s.

Founded in 2009, Mäag’s eponymous company Mäag Audio offer a focused product line-up comprising three 500-series units (the PreQ4, EQ2 and EQ4), two native plug-ins made in association with Plugin Alliance (EQ2 and EQ4, the latter also being available on the UAD DSP platform), the EQ4M, which is a 1U, dual-channel, rackmount version of the EQ4, and the all-new Magnum-K, which is the subject of this review. This 1U, single-channel rackmount unit features two separate, series compressor stages, which run in parallel with Mäag’s EQ2 Air Band equaliser. It’s an intriguing product paradigm that I don’t recall having seen before.

Solid Air

The first thing to strike me about the Magnum-K was a confidence-inspiring solidity and quality — this thing is built to last! It boasts a heavy-gauge steel chassis, positive-action switches and 20-position detented knobs. These sit in a substantial front panel, on which the umlaut in the Mäag Audio logo is illuminated by twin orange micro-LEDs. Inside, a single circuit board carries, alongside an onboard mains power supply, WIMA capacitors and other components of similarly reputable provenance.

As you’ll see from the photographs, the front panel isn’t short of knobs and switches, and you might think that the spacing could be a little tight in places, particularly in the Magnum Compressor section. But in practice, the slim knob design and intelligent positioning of controls in relation to each other combined to give me an unexpected feeling of spaciousness.

The first control in the Magnum-K signal path is Input Attenuation, which can reduce the level of an incoming signal by up to -12dB, enabling you to tame the output of, for example, a mic pre when you’re pushing its output transformer. A separate Input Gain control follows, giving you up to +12dB of boost to play with. Sitting between the two, you’ll find Signal Present (-30dBu threshold) and Peak (lights at 3dBu below the 26dBu clip point) LEDs.

Next, the signal enters the Magnum optical compressor, in which Mäag Audio have taken an operational approach that I’ve not encountered before in hardware. The signal entering the Magnum’s side-chain is compressed, restricting the range of gain reduction being applied by the unit’s optical gain element to the main signal to 4, 8, 12 or 16 dB. This helps you to avoid over-compression. The detented Ratio, Threshold, Attack and Release controls give you complete (and repeatable, if you make a note of their positions) control of the amount, onset point and speed of the selected compression range. The amount of compression being applied is ‘metered’ on a single blue LED that gets brighter as the amount of gain reduction increases.

A six-position switch either inserts high-pass filters at 40, 80, 120 or 220 Hz into the side-chain or accesses the rear-panel side-chain loop into which, for example, you could insert an external EQ for de-essing purposes. The final control in this section is the button that switches the Magnum between feedback and feed-forward operation, allowing you to choose between these two distinctly different-sounding styles of compression.

The output of the Magnum stage feeds the K-comp compressor. This fully independent optical compressor is focused on the 3kHz region, which is where harshness and edginess reside. Switching in the K-comp enables you to control the level of dynamics in this part of the audio spectrum without having to accept the compromises that using EQ or broadband compression can require you to make. Other than its In/Out switch, the only other K-compressor control is that for the Threshold level; and, as in the Magnum stage, a single blue LED increases in brightness with the level of compression being applied.

The twin-band EQ2 equaliser, the controls of which take up most of the right-hand half of the front panel, acts only on the source signal. When engaged, its output is mixed with the compressed signal just prior to the Make-up Gain control. You can use this latter control either to balance the level of the combined signals with the original, unprocessed signal, or to push up the level into the final Soft Limiter stage, giving you a few final dB of compression to (as Cliff Mäag picturesquely puts it) “trim the trees”. To give you visual indication of what’s going on whilst you’re doing this, a Peak LED above the Make-up Gain knob illuminates at 26dBu (3dBu below clipping) and a tricolour LED, sitting below the limiter In/Out switch, transitions from green to pink to red as the level of soft limiting increases.

The EQ2 equaliser features a rather unique implementation of a two-band EQ. Firstly, it is purely additive and, secondly, its operational range is limited in the Low/Mid band to 11 frequencies between 1.4kHz and a subterranean 10Hz, the actual frequency and boost being dependent on the Q of the lower LMF band’s bell-shaped boost, which can be switched between Tight (one octave and up to 12dB of gain) and Wide (two octaves with up to 15dB of gain). The Air Band offers a shelving-type boost of up to12dB across six selected frequencies between 10 and 40 kHz.

Although the frequencies in the Magnum-K’s EQ2 low/mid band are identical to those of both the plug-in and 500-series versions, its Air Band substitutes 25 and 30 kHz corner frequencies for the 2.5 and 5 kHz found in the other incarnations. In terms of physical controls, each band has its own frequency selector, In/Out switch and Gain control. In practice, the two Gain controls act in a manner analogous to conventional wet/dry controls for each band, as they determine the level of EQ’d dry signal being mixed with the compressed signal prior to the make-up gain stage.

To complete the front-panel roll-call, there’s a Link switch that links the Ratio, Threshold, Attack and Release controls of two units being run as a stereo pair and an Engage switch that brings the Magnum-K out of its hard-wired true bypass.

The Magnum-K’s rear panel offers external access to the side-chain, as well as the ability to link two units for stereo operation. The Magnum-K’s rear panel offers external access to the side-chain, as well as the ability to link two units for stereo operation.

In Use

Since the Magnum-K really is a quite unique piece of hardware, I did have to rethink somewhat my approach to both compression and EQ. At face value, the Magnum-K seemed blindingly simple, but the more that I worked with it, the more I came to realise just how subtle and complex a processor it can be.

In terms of raw sonic performance, the Mäag Magnum-K is up there with the best that there is, with a clear, open, effortless nature that you’d expect from its quoted frequency response of 20Hz to 40kHz (±1dB) and headroom of +28dBu. The preset compression ranges in the Magnum compressor were a new experience in hardware, but I quickly began to appreciate just how useful these are in enabling me to quickly select an appropriate value for the track in question — for example, 4dB on a vocal track — and then work with the side-chain filter, ratio, threshold, attack and release within that range to get the compression sounding ‘right’ without straying into over-compression.

The feedback and feed-forward styles of compression are, as I said earlier, very different beasts. Feedback compressors derive their side-chain control signal after the gain-reduction stage, so the gain reduction is being driven by an already compressed signal, whereas in a feed-forward situation, the gain reduction responds to the original signal in its uncompressed state. In a feedback compressor, the attack and release times are influenced by both the amount of gain reduction and the compression ratio in use, so their controls become slightly more arbitrary than they are in a feed-forward design, where the values remain uninfluenced by the material passing through them. This means that control positions set under one style will have a very different effect on the signal when switched to the other. According to Cliff Mäag, the Magnum compressor, when set to 16dB range and feed-forward operation will deliver over 30dB of compression when being driven hard with the Ratio control at maximum — which might be useful for somebody, some day.

The K-comp is the first time that I’ve come across a second independent compressor stage in hardware dedicated to taming a fixed frequency in an already compressed signal, and it does a very effective job of reducing any harshness around the 3kHz mark. I’ve occasionally used cascaded compressors in a DAW effects chain with a narrow mid-range band-pass filter in the side-chain of the first one, either to de-ess or to pull back some of the harshness in a vocal before applying broadband compression with the second. I don’t recall ever having tried putting the broadband compression first — but I will, soon!

Then there’s the EQ2 section. To me, this is something quite special, as it has a seemingly effortless ability to add weight, richness, sparkle and ‘air’ to any signal passing through it without introducing any unwanted artifacts other than the inevitable increase in level. Impressive and extremely effective as the low/mid LMF band can be at adding weight and richness, it’s the Air Band that does it for me. This is one function that I’d probably end up leaving permanently in circuit when tracking, setting it somewhere between 25 and 40 kHz depending on microphone and source. With its apparent ability to enhance frequencies below the selected corner frequency without causing any side-effects, the Air Band is the ideal companion for vintage ribbon mics in particular. I was fortunate to have a pair of Magnum-Ks for review, and running my Bang & Olufsen BM-5 stereo ribbon mic through them with their Air Bands set at quite a hefty boost at 25kHz gave me a stunning acoustic guitar sound. I don’t use my B&O for vocals in the normal scheme of things but, having worked with Air Band, I probably would.

When using the EQ2, I did miss having a physical ‘wet/dry’ mix control between the compressed signal and the EQ2’s output, and I personally would have liked there to be a single-button EQ bypass in addition to the individual band in/out switches, just to make A/B comparisons a simpler operation. But these aren’t deal-breakers for me by any stretch of the imagination — they’d just be nice additions.

Mention of the pair of Magnum-Ks brings me neatly to another application to which these units are well suited — stereo mix-bus processing. I’m not a specialist mastering engineer by any means, but the way in which careful use of the Magnum-K’s linked compressors, together with their EQ2 stages and soft limiters, enhanced rough mixes of tracks intended for my band’s next CD was more than impressive, both when running in stereo or as separate Mid-Sides components. I’m certain that any experienced mastering engineer would get a lot more out of the Magnum-K than I did, but I’ll definitely be trying to find a way to get my hands on a pair for my next set of final mixes.


More than anything else, to my way of thinking the Mäag Audio Magnum-K Compressor is a unit that reflects its designer’s personal studio engineering experience and workflow requirements. A well thought-out, intuitive (and unique) ‘four-in-one’ combination of optical compression and boost-only EQ, the Magnum-K looks set to carve out a new niche in pro-audio hardware.

The purchase price naturally reflects its build quality, level of audio performance and professional nature, but the Magnum-K, in reality, offers excellent value for the performance on offer. It’s a unit that every serious studio and mastering engineer should at least audition, and it might also be an attractive proposition for studio-equipment hire companies. Those of us with lower budgets may have to dream, but ultimately, this is a very impressive processor indeed, and one which I highly recommend.


There is nothing comparable that I know of in a single hardware unit, but if you are into the 500-series ‘Lunchbox’ format, you could achieve a similar result with two channels of high-quality compression and a Mäag Audio EQ2-500 Series. Since the EQ2 is also available as a DAW plug-in, you’ve also got the option of creating a similar software effects chain.


  • Well thought-out and intuitive to operate.
  • Unique ‘four-in-one’ approach.
  • Superb audio performance.
  • Wide range of possible uses, from ribbon-mic recording to bus compression.


  • Unfortunately, this kind of quality doesn’t come cheap!


This unique ‘four-in-one’ combination of two optical compressors and a two-band boost-only EQ opens up a new hardware-based approach to track and mix-bus dynamics and equalisation. It isn’t cheap, but quality and performance at this level never is. Highly recommended.


£2299 each including VAT.

KMR Audio +44 (0)20 84452446

$2395 each.

Mäag Audio +1 801 616 3685.