The boutique amp market thrives and exists as it does today largely thanks to the pioneering efforts and success of Mike Soldano.
Before Soldano introduced the legendary SLO-100 Super Lead Overdrive 100-watt head in 1987, the most viable high-gain amp options for hard rock, metal and shred guitarists were mostly limited to either Mesa/Boogie models or a Marshall or Fender amp that was hot-rodded by an amp tech.
The immediate success of the SLO-100, which was warmly embraced by an impressive variety of pros, gave dozens of amp techs the encouragement they needed to start their own amp companies, particularly those expanding the range of high-gain designs, and a few years later the boutique amp phenomenon was in full swing.
Although Soldano previously had performed numerous guitar amp mods himself, his design for the SLO-100 was not based on a pre-existing model with a few upgrades but rather delivered an entirely new circuit.
The power amp section is based on a classic Western Electric circuit using a quartet of 6L6/5881 tubes, but the unique preamp circuit features five cascading gain stages that employ five 12AX7 tubes.
While its Normal and Overdrive channels share a single set of bass, middle and treble EQ controls, each channel has its own preamp gain and master volume controls to give users greater textural flexibility. The Normal channel also includes a switch for selecting Clean or Crunch character.
The SLO-100 Overdrive channel’s tight, dynamically expressive and harmonically rich high-gain tones and smooth attack instantly earned it a devoted following of hard rock and metal players like Warren DeMartini, George Lynch, Matthias Jabs and Mick Mars.
Eddie Van Halen used an SLO-100 during the early ’90s to record For Unlawful Carnal Knowledge, and the amp later significantly inspired the design of his signature Peavey 5150 model. Joe Satriani relied heavily on an SLO-100 when recording The Extremist.
Apparently the amp pairs quite well with David Coverdale’s vocals, as Vivian Campbell, Adrian Vandenberg and Steve Vai used SLO-100s during their stints with Whitesnake, and Jimmy Page used an SLO-100 to record tracks for the Coverdale/Page album.
However, the SLO-100 may be even more famous (and enduring) for its early adoption by blues rockers like Eric Clapton during his Journeyman and 24 Nights era, Gary Moore for his early ’90s tours and Warren Haynes with Gov’t Mule and the Allman Brothers Band (he even convinced Dickey Betts to use an SLO-100 for a while with the Allmans).
Mark Knopfler and Lou Reed proved that the SLO-100 delivers clean and overdrive tones that are equally as impressive as its more aggressive high-gain distortion textures.
The Normal channel’s Clean setting provides very distinctive clean tones that are crisp and slinky – similar to the tone of a guitar plugged directly into a mixing console – that is ideal for funk rhythm playing. This, along with its overdrive and distortion tones, made the Soldano one of Prince’s preferred amps during the late ’80s and early ’90s.
Soldano still offers the SLO-100 model today, now called the SLO-100 Classic. The Classic features a handful of changes and upgrades, including the addition of a Depth control, front panel channel switching and a Level control for the effects loop.
