Review: Warm Audio WA-MPX

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Review: Warm Audio WA-MPX

Warm Audio WA-MPX
Words By Lewis Noke Edwards

Warm Audio WA-MPX | Studio Connections | RRP: $1355

Warm Audio have been making a name for themselves for some time now. Their accessible pricing has put them in the studios of budding beat makers and producers, while the quality of their sound makes them great contenders even up against equipment five times their price. While Warm Audio produces equipment based on famous circuits, they also reimagine them for a modern world, with all the controls of the original units, plus more handy filters, side chains and switches to further shape your sound if you need to. 

Read more gear reviews here.

Their latest foray, and—spoiler alert— home run, is the WA-MPX, a single channel tube preamp based on the famous Ampex 351 tube preamps that were originally used to treat sound before it hit a tape machine. There’s also a stereo version available, the WA-2MPX for those of us who like to have pairs of this kind of thing! Both units are a 2U affair, with VU metres for input level, and switchable mic/line/instrument inputs, the instrument input being easily accessible on the front of the WA-MPX. There’s lots of robust switches to toggle on and off different tone shaping options, as well as input, output and Tape Sat controls so you can drive those tubes if you want!

The WA-MPX is a single channel tube preamplifier. Powered by two 12AX7 & one 12AU7, the WA-MPX offers 90dB of gain – plenty for almost any source, and with headroom to boot. The Preamplifier Input control allows you to push the signal, while the Output Level can trim it before your converter/interface. As is standard there’s controls for phantom power and polarity switching, but the WA-MPX also has additional switches like High Gain, Tone and high and low pass filters. The filters are set at 80Hz and 2kHz, 80Hz for a hi-pass filter (HPF) and the low-pass filter (LPF) at 2kHz. While these may sound extreme, the roll off is very subtle and instead shifts the tube focus to the mids for clarity while slowly rolling off highs, lows, or both. The aforementioned High Gain adds 20dB of gain at the flick of a switch, and Tone switches the resistance of the input transformer for adjusted impedance and a brighter sound. The WA-MPX is fully discrete, and has large-core CineMag USA Transformers at the input and output stages for clarity and headroom. Inputs and outputs are accessed via XLR, TRS or TS inputs, and outputs are XLR or TRS. The unit reproduces everything from 20Hz-20kHz, so it’s equally good for low frequency sources as it is for anything else.

The WA-MPX features hand-wound, large-core CineMag USA Transformers at the input and output stage for unmatched headroom. What this means is that you can drive the input super hard without clipping the output stage or other components, and the resulting tone is warm, fat and crisp all at once, without being unmanageable. The Preamplifier Input is entirely usable when dimed or set ‘correctly’ (ugh, boring), and while you’ll hear the grit quite audibly, the shape of the transients are nice without being entirely squashed, fuzzy or harsh. The Output Level helps to trim the newly reborn gritty, warm signal before it gets sent out to your interface, converter or Ampex tape machine to be recorded. This can be pushed further with the High Gain control, conventionally used to give lower gain sources 20dB, but can be toggled on and off to reach the maximum 90dB of gain available. The toggle switches are really what moves the WA-MPX into a league of its own.

While the WA-MPX is  a preamp at its core, the toggle switches on the front of the unit make it so much more than that. EQs on preamps are nice, but the toggles on the WA-MPX make it fast. There’s limits to what you can do, but the controls it does have help you filter and drive the signal quickly so you can focus on the recording. A quick switch to reduce sub-80Hz rumble, or soften the high end with the 2kHz LPF and you’ve got a treated signal at the ready. Dynamics too? The WA-MPX can soften and squash as much as you please.

The Tape Sat control isn’t a conventional dynamics control, but it introduces harmonic distortion and that natural ‘tapey’ compression. The Tape Sat control distorts the signal, and both softens the transients and closes the dynamic range for a well treated, controlled and punchy sound.

The WA-MPX is something stellar. The original Ampex 351s are very hard to come by – but why would you even try, now that Warm Audio has come to the table? Available in both single and dual channel versions, the WA-MPX and WA-2MPX are super robust preamplifiers with as much gain as you might need, and some tonal shaping controls to quickly help your signal fit into an arrangement. The vintage-correct components make for a very clean preamp with plenty of gain and headroom, but with the controls and ability to obliterate the signal when needed. It’s somehow both a utility preamp and a vibey colour box in one, being usable on everything, but with the option to drive, distort and filter depending on how much you like to commit when recording. The WA-MPX is the real deal, melding the past and present together and driving it through classic components in the modern day.

For more information, head to Warm Audio. For local enquiries, visit Studio Connections.