ART Solo MPA
Review by Paul Vnuk Jr.
A multitude of tones and textures in an affordable microphone preamp
At this year’s winter NAMM show, Applied Research and Technology (ART) announced their new Solo Series: the Solo VLA compressor, the Solo MPA preamp and the Solo Studio channel strip. We will look at all three (and more) in the coming months, but today, we start with the Solo MPA—a single-channel, multi-voice tube preamplifier.
Going Solo in Style
Each member of the Solo Series is a single-channel/mono unit in a 1U 19″ rackmount enclosure with a short 6″ depth. All three share the same black, brushed-metal appearance and layout (give or take a control or two). This includes a large round traditional backlit VU meter that, on the Solo MPA, functions as an output meter.
Find Your Voice
The Solo MPA is billed as a multi-voice microphone preamp. As such, it is both a solid-state and a tube-based mic preamp, with the ability to blend between the two ‘voices.’ The Solo MPA also offers four 31-position detented knobs dedicated to further tone shaping, which we will dig into momentarily.
The Solo MPA includes three LED-equipped push buttons for +48v phantom power, phase and a +20dB gain boost (rather than a pad). On each end are stepped knobs for input gain (0 to +40dB) and master output (∞ to +15dB). The Solo MPA is capable of 75dB of overall gain—perfect for any mic or occasion.
The Solo MPA includes a front-side power switch and a 1/4” TS-switching instrument input.
Connections on the rear of the unit include both balanced XLR and 1/4” TRS I/O, along with a 3-prong IEC power socket for the ample internal toroidal power supply (no wall warts here), which contributes nicely to the unit’s 5.6lbs. heft.
Tailoring the Tones
Moving to the four tone-shapers, the first up is a variable impedance control with a range of 600Ω to 15kΩ centered to 80kΩ. Impedance (measured in Ohms or Ω) refers to the resistance of the signal from the mic into the mic pre.
All microphones have an output impedance from 30Ω up to 600Ω, and most modern microphone preamps offer a fixed input impedance that is approximately 10x that on average—15kΩ typically for most modern mics—and we don’t typically need to worry about it.
On the other hand, when a preamp offers switchable or, in this case, variable impedance options, altering the loading of the impedance relationship can change the mic’s tonal reaction—most noticeable on passive dynamic and ribbon mics.
The result is like an EQ of sorts—darker and rounder at lower settings and brighter and more detailed at higher settings. However, it’s more than EQ; impedance can make a mic sound more congested and blunt or open and airy. Even more exciting, the results can differ from mic to mic. This is very much a “dial it till it sounds good to you” kind of control—the manual also includes some tips and starting points.
Pass and Tilt
Next is a fully variable 10 Hz to 200 Hz low cut (high-pass) filter followed by a simple yet effective Tilt EQ. This one-knob EQ offers ±12dB of simultaneous boost/gain with a center frequency pivot point of 1 kHz—as you boost the treble, it cuts/attenuates the low-end in relative and equal amounts, and vice versa––kind of a seesaw EQ.
Solid-State or Tube The Solo MPA preamp boasts a 15 Hz–50 kHz (+0dB/-1dB) frequency response, a dynamic range of >110dBA, a CMRR of >90dB, a THD of <0.005% and an Equivalent Input Noise of -129dBu A. It starts clean, clear and detailed on the solid-state side, and from there, you can blend in a warm, rich and bold tube stage using a Psvane ECC 88 tube, resulting in a noticeably thicker tone at full.
In Use
In a day and age when low-cost classic gear “clones” are all the rage, it’s easy to forget that ART has been paving its own affordable sonic path for 40 years. The Solo MPA is designed to have its own versatile sound rather than to capture a specific classic vibe of any famous preamps from the past.
That said, turning the tube voice to full instantly imparts a thick warmth that we often associate with vintage tube gear. On the solid-state side, the Solo MPA is clean and stays out of the way. Remember, you can easily blend between the two, along with further sonic fine-tuning with the impedance, high-pass and tilt-EQ, to find the perfect sound for your track.
Despite the one-knob-only simplicity of the Tilt EQ, low cut, variable impedance and tube blending, the Solo MPA boasts a wide sonic palette well suited to a wide range of sources and microphones.
Rough It Up
For those who like their sound a tad rough—especially on direct bass or electric guitar—the Solo MPA can be easily pushed into overdrive and pulled back with the master output to avoid clipping your converters. While it’s easy to lean on the tube side here (especially on vocals and bass), I quite liked the edge that the overdriven sold-state side lent to direct electric guitar.
Final Thoughts
In a world where the stock preamps found on most budget audio interfaces and compact mixers (analog and digital) trend toward the utilitarian and vanilla side of the sonic spectrum, the ART Solo MPA makes its mark. It offers both clean solid-state and/or rich tube tones along with 75dB of gain. Its well-curated selection of creative tone-shaping options includes features rarely found in mic-pre-equipped interfaces or many stand-alone preamps, budget or otherwise. All of this combines to make the Solo MPA a more than impressive box, especially when you consider its price.
The ART Solo MPA retails for $299, making it perfect for both novice engineers and seasoned pros looking for a new, creative tonal tool for their arsenal.
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