Universal Audio SOLO 610 and SOLO 110 Preamp-DIs
These days, anyone can get a respectable multi-track recording rig for about a month’s pay. But for most of the recorded-music era, making a decent sounding recording has required access to a studio because it had high-quality gear—microphones, EQs, compressors, and more—that most people couldn’t afford. Central was the recording console itself, made up of numerous channel strips. Each contained preamp circuitry of such reliably high quality that engineers could count on them for direct recording. That’s why many small project studios rely on standalone preamps designed after vintage channel strips, especially for recording with microphones and tracking bass direct, just like it was done on many classic album sessions.
One company making this kind of gear today is a direct descendent of a recording gear pioneer. Bill Putnam Sr. created the modern recording console, was the first to use artificial reverb and multi-band EQ, and developed many now-classic pieces of recording gear through his company, Universal Audio, later called Universal Recording Electronics Industries (UREI). Putnam died in 1989, and in the late ’90s, his sons revived the business, which has the dual focus of making software plug-ins that emulate classic gear, and continuing to offer analog hardware evolved from Putnam’s original designs. The SOLO/610 is the latest UA hardware product based around vintage Putnam circuitry. A tube mic preamp/DI with an instrument input and a thru output for sending a signal to an amp, the 610 is based on a channel strip of Putnam’s UA 610 console, but it comes in a portable package that’s easily transportable from amp-top to desktop, and rugged enough to sit on the floor. The similarly shaped SOLO/110 has identical functions and features, but is based on more recently developed solid-state circuitry designed for clarity and high fidelity. Both are hand-assembled in the U.S.
While most preamps are designed for rack-living, the SOLOs are built to go, and can work a double without batting an eye: swing shift as a home-studio preamp, followed by graveyard as a DI on a gig or in a bigger studio. And they’re rugged enough to survive such a transient life. Smaller than a breadbox but with roughly the same dimensions, the SOLOs have handy top-mounted carry-straps, chassis ends that extend beyond the front and rear panels to protect the controls, and stylish UA-logo shaped side cooling vents. Each SOLO has a bright blue LED that lights up when the power is on, and a second, tri-color LED that serves as a level meter, turning first from green to amber when the input signal approaches clipping, then to red when it overloads. The front panels house chunky gain and level knobs, q" input and thru jacks, and switches for mic or line input, low or high impedance, low-cut filter, phantom power, and phase-reverse, which can be helpful when using multiple mics on the same source. Xlr in and out jacks are on the rear, along with a mic level/line level selector and a ground-lift switch.
Though the broad aesthetic strokes are the same, the 610 and 110 each have distinctive styling, with vintage style knobs and rugged metal toggle switches on the 610 and plain knobs with illuminated push-button switches on the 110. Inside, the 110 and 610 are pretty different. While both use high quality components like Mogami premium wiring and custom-wound transformers, the old-school 610 has 12AX7 input and 12AY7 output tubes, high-quality WIMA polyproplene capacitors, and a linear power supply. The audio signal never goes through any transistors. In contrast, the 110’s transistor-loaded circuitboard has a switchmode power supply and no output transformer, instead using a Class A, DC-coupled FET output.
Universal Audio designed the two SOLOs to cover the entire range of mic and DI amplification between them, with each one favoring certain sources. For bass, UA recommends the SOLO/610 for its warm tube sound, but I auditioned both units with a mellow, flatwound-strung Fender Precision and a fairly hot and zingy Music Man StingRay. I also tried them on vocals. The SOLOs made gain setting a cinch, with big, honking knobs that have considerable range and precision, and those tri-color LEDs. The tube-loaded 610 can go from completely clean to mild tube fuzz. Nudging up the gain on the solid-state 110 also adds rich color before it goes into the red.
Before trying out the SOLOs, I tracked the basses directly through my audio interface to establish a comparison basis. Through the SOLO/610, the already warm P-Bass became thicker and girthier at the bottom, filling the track with a sweet plushness. On its own, the StingRay sounded a tad harsh, but it felt more balanced and smooth through the 610, without losing any of its articulate attack. Both benefited from a slight low-mid bump. Conversely the SOLO/110 was more about clarity and transparency, but it was hardly lacking for warmth. It had an open-sounding top end, which was more beneficial on vocals than bass. After some experimentation, I opted for the 610 and the P-Bass for a home demo of a pop song. The sound was fat, luscious, dynamic, and simply sublime. It was inspiring; I ended up using the 610 for rhythm guitar as well.
Though sonically distinct, either SOLO would be a versatile tool-kit addition, especially for bassists who split their time between studio and stage. They could each even be paired with a power amp as part of a high-end rig. The SOLOs are bulkier than a typical DI, and they may lack the EQ or compressor circuit of other channel-strip style preamps, but there’s something to be said for a simple, versatile preamp that’s built to go anywhere. The SOLO/610 shines on bass, but if your music demands transparency and clarity, you won’t be disappointed with the SOLO/110.
Universal Audio SOLO/610
List $949
Street $800
Pros Warm sounds, flexible functions, handy form factor
Cons None
Bottom Line Vintage channel-strip built to go
Universal Audio SOLO/110
List $949
Street $800
Pros Clarity without coldness, flexible functions, handy form factor
Cons None
Bottom Line Flexible hi-fi preamp in a lunchbox
TECH SPECS
Circuit Topology SOLO/610, all-tube; SOLO/110, Class A discrete solid-state
Input impedance mic, 500Ω or 2kΩ; di, 4.7kΩ or 2.2MΩ
Front panel jacks 1/4" di; 1/4" thru;
Front panel controls gain, level, mic/di, lo-z, hi-z, phantom power, lo-cut/flat, phase switch
Back panel jacks xlr mic input, xlr output
Back panel controls power, mic/line, ground lift
Frequency response SOLO/610, 20Hz–20kHz; SOLO/110, 10Hz–60kHz
Dimensions 15" x 4.5" x 5.75"
Weight SOLO/610, 7.5 lbs.; SOLO/110, 5 lbs.
Warranty One year limited
Made in USA
