Universal Audio's involvement in the professional audio business goes back a long way - the original company's products date back to Bill Putnam Sr.'s groundbreaking designs back in the 1950s. Now Universal Audio has added two new preamps to its line-up: The Solo/110 and Solo/610.

The two Solos are nearly identical externally; but inside they're very different animals. The tube-based Solo/610 is based on the historic original 610 console Putnam built, which was used by artists ranging from Sinatra to Van Halen. The solid-state Solo/110 is a discrete Class A preamp based on Universal Audio's high-end Precision 8110 and 4110 models.

Both models are housed in the same rugged steel "desktop"-style enclosure, which has a convenient handle on top and an angled front panel that makes seeing settings easy. This form factor makes it easy to grab a Solo and place it in the studio near a microphone, to take it on location, or to position it near your computer, recorder, or mixer. You can rackmount up to three units side-by-side using an optional rackmount shelf.

Aside from the fact that the two units have different circuits inside, each has its own types of switches and knobs - the 610 goes for big "vintage"-style knobs and toggle switches, the 110 has lighted pushbutton switches and streamlined "modern" knobs.

Both preamps have a DI input (with a DI thru connection for routing the signal to a guitar or bass amp), high and low input impedance settings, switchable phantom power, a low-cut filter, and a phase (polarity) switch on their front panels. Knobs are provided for controlling input gain and output level; a tri-color LED shows signal present, near clipping, and clipping. Around back, each has a power switch and IEC power cable connection, an XLR mic input, and an XLR output with switchable mic/line level setting and ground lift switch.

You might think that "straight-ahead" preamps like the Solo series have just one sound. But in fact, these are quite versatile units. First up, you can alter the tone of the preamps by changing the input impedance. Beyond this, you can dial in the tone to taste using the gain structure of the preamp. By running the input gain control lower and the output level higher, you get a clean, transparent tone. Turn up the input gain and turn the output down, and you get a fatter, more harmonically rich tone. It works sort of like a guitar amp - turn the preamp up for more drive, and use the output control to set the final volume.

Although they're operationally identical, naturally there are tonal differences between the 610 and 110. The 110 tends toward a clear, pristine, sound, without a lot of coloration - perfect for when you want to capture a natural, realistic sound. I found that it compared favorably to some of the high-end "straight-wire" preamps in my studio. As you turn up the gain, the 610 has all the tube "girth" and punch that you'd expect from a vintage design - we're talking fat, with a smooth top end. It's great for rounding out and warming up a signal.

Whether you're looking for a pure, clean sound or a vintage tube-ified tone, the Solo/110 and Solo/610 deliver. They're compact, convenient, and decidedly affordable. In fact, you'll want both; I found the two units were perfectly complementary to one another. Where one wasn't right for a signal, the other stepped right in and sounded great. Both are clean, quiet, rugged, and easy to use. Universal Audio has a pair of winners on their hands with the new Solo preamps!