Mike Soldano. I Set Out to Build an Amp for Myself

Seattle, the 1970s.

Young Mike cares far more about cars than about electronics. He is into street racing, works on his Chevrolet Camaro, is good with his hands and knows how to build and rebuild machines.

Then he hears Cream’s Badge and Eric Clapton’s solo.

It is not the speed or the virtuosity that gets him. It is the sound itself: the electric guitar really sings, cries, speaks with a human voice.

Mike decides he has to learn to play like that.

And he starts fairly late, at about 20 or 21. He tries his father’s acoustic guitar, but soon realizes he needs a completely different instrument.

He buys a used electric guitar and a tube amp, a homemade copy of a Fender Bassman.

And then comes the trouble that changes his life: the amp keeps breaking down.

There is no money for a repairman. He has to figure it out himself.

Later Soldano would put the whole story very simply: when you have no money, you have to get creative.

He studies schematics, repairs gear and starts building his own guitars. In 1977 he opens a small guitar workshop. By 1980 he is already playing Seattle clubs with bands.

But there is one problem.

He does not like the sound of his amps. Not even the expensive ones.

In the early 1980s Marshall and Mesa/Boogie are already around. Guitarists are busy experimenting with modified amps.

Soldano likes the Mesa’s gain, but he does not like how single notes smear at high gain. As he explains it himself, there was not much string-to-string definition: hit a complex chord like a D9 and instead of separate strings you hear mud.

He wants all of it at once:

In 1981 he gets serious about tube electronics. He reads radio textbooks from the 1950s, studies schematics and experiments after his day job, sometimes late into the night.

He repairs and modifies Fenders and Marshalls and works at the well-known Stars Guitars in San Francisco. Every mod teaches him something.

That is how an experimental amp with the wonderful name Mr. Science comes about. A piece of plywood with electronic components mounted on it, a test bed for experiments.

By about 1985 or 1986 Mr. Science has turned into the prototype of the future SLO-100.

Mike starts taking it to his own gigs. Other guitarists hear the sound and ask whether he could build one for them too.

Soldano later admitted that he never planned to build a big company. He simply found out that other people wanted the sound he had built for himself.

In 1985 Soldano has three people who want to buy an amp. He buys parts and builds the amps in the basement of his parents' house.

But of the three who promised to buy, only one follows through and pays.

Mike is left with two amps nobody wants and a whole pile of parts.

And he makes a rather crazy decision.

He puts a new motor in his old 1938 Chevrolet, loads it with the amps, the experimental Mr. Science and the parts, and heads for Los Angeles.

That is where the studios, the record companies and the world-class guitarists are.

He tries to set up meetings with the stars and cold-calls their managers. Almost all of them promise to come, and then they are no-shows.

Little by little the money runs out.

His first workshop in Los Angeles is in a former bordello. Now and then people dropped in there who had no intention of buying an amp.

To survive, he repairs guitars, picks up odd jobs and works as a roadie at shows.

But one day the first real stroke of luck comes: Howard Leese, the guitarist of Heart, tries his amp.

Within two chords Leese decided to buy amp No. 002.

The next important customer is Steve Lukather of Toto.

But sales are far too slow. By the end of 1987 Mike is practically broke. He is seriously thinking about giving it all up and going back to Seattle.

One night Mike comes home around four in the morning after a roadie job for the band Vixen.

The message light on his answering machine is blinking.

He presses play.

The first message is from Lou Reed.

The second is from Vivian Campbell.

The third is from Michael Landau.

Three people from rock music’s top league are looking for an unknown builder to talk about his amps.

At first Mike thinks one of his friends is pulling a prank on him.

But the calls are the real deal.

And from there things move fast.

By the spring of 1988 Soldano already has back orders, and in the summer Eric Clapton, Mark Knopfler and the Scorpions order his amps. The back orders stretch to about six months.

The man who was ready to close his shop suddenly cannot build amps fast enough for famous musicians.

The SLO-100, the Super Lead Overdrive introduced in 1987, is no longer just a modified Marshall but a circuit of its own, designed around Soldano’s own idea of overdrive.

So what was new about the engineering?

Not the invention of tube overdrive: cascaded gain stages existed long before Soldano.

It was how he arranged them.

In the SLO-100 the signal goes through several gain stages in a row. Mike tunes the gain, the frequency shaping and the operating points of the tubes so that he gets huge overdrive without losing articulation.

The design uses five 12AX7s, four in the preamp and one in the phase inverter, and four 6L6/5881s in the power amp.

Soldano did not just add even more gain. He learned to control the character of that gain.

And the result turned out surprisingly versatile.

The amp won over not only hard rock and metal players but also Clapton, Knopfler, Gary Moore and Warren Haynes. In the early 1990s Eddie Van Halen used an SLO-100 to record For Unlawful Carnal Knowledge. Later the Soldano design had a strong influence on the Peavey 5150.

The SLO-100 became one of the benchmarks for the next generation of high-gain amps.

Soldano explains his overdrive in a language he knew long before tubes: the language of a manual transmission.

Take off in first gear and go straight into fourth, and you lug the engine: it stumbles, shudders and jerks along. That is how almost everybody did high gain back then: jam the signal through one tube and clip the hell out of it. The gain came out scratchy, lacked tone and was hard to control. Shift through all four gears, and the engine runs smoothly and at its full potential.

In the SLO-100 every gear is a tube stage. The first stage simply amplifies the signal. The next one starts clipping, but only a little, just enough that the distortion and compression leave the fundamental intact. Then another stage, and another, until the signal reaches full gain. The fundamental harmonics, where the bass and the fullness live, come through the whole chain intact, and the overtones build on top. That is where the sweet, singing overdrive without mud comes from.

The SLO-100 has five 12AX7s, and each one holds two triodes in a single glass bottle, so that makes ten stages. But only four of them are gears. The other six have other jobs. One belongs to the clean channel only. Two cathode followers buffer the effects loop and the tone stack so that these do not load down the signal. Another recovers the gain lost in the effects loop. The last two are the phase inverter that drives the power amp.

Now the scale. In an old Fender Twin or a Marshall Plexi the signal path from the input jack to the power section is short: few tube stages, not much voltage gain. In the SLO-100 the potential voltage gain is over a million. When a note is picked, the pickup puts out around one volt, sometimes more, but there will be no million volts at the output: the tubes clip and cut the signal off at their ceiling.

The same clipping gives the sustain. While the string is loud, the tubes clip the signal at one level. As the note decays, there is less clipping, and the output hardly drops. That is why the SLO holds a note almost forever, until the string’s signal falls below the clipping threshold. Only then does the note really decay.

The second trick sits at the input. The heavy bass strings put out a stronger signal than the light ones, break up sooner and get compressed harder, and the bottom end gets lost. So right at the input Soldano cuts a little gain in the lows and adds some in the highs. By the last stages the signal is even from low to high, and the low notes are not crushed by distortion. Soldano openly admits he is not the only guy who does this.

The power amp of the SLO-100, by contrast, is a classic: the good old Western Electric circuit, the same one as in Fender Bassmans and Marshalls. The tone is born in the preamp, and that is where Soldano put his own ideas. All in all he spent about four years developing the SLO-100, fine-tuning it by ear.

Soldano has one measure of success: transparency. A Telecaster through an SLO should sound like a Telecaster, a Strat like a Strat, a Les Paul like a Les Paul, even with the gain cranked. With a clean amp that is easy, with high gain it is hard. That is why the stages of the SLO are designed to work together: each one does a little, and none of them chokes the guitar.

Hence the name: Super Lead Overdrive. The overdrive is built into the amp itself, and it needs no pedal for high gain.

Full-size schematic

And then something especially interesting happened from an engineering point of view.

In the late 1980s big guitar rack systems were developing fast. The stars used separate preamps, power amps, switchers, reverbs and delays.

Bob Bradshaw, the famous designer of such systems, suggested that Soldano build a three-channel rack preamp.

That is how the Soldano X88R came out, around 1988.

The idea was to bring three different amp voices together:

These units became an important part of professional rack systems, Steve Lukather’s among them.

Today’s line of Soldano rack preamps, the X88-IR included, descends from the X88R. It is not just one more amp with a famous name on it, but the continuation of a design that grew out of the early era of professional guitar rack systems.

Soldano never turned into the head of a giant corporation.

For decades his business stayed a small specialist company.

In 2010, for example, Seattle Business described the Soldano workshop where Mike ran the company with just three employees. At the time it built about 250 amps a year.

In 2019 Soldano sold the company to Boutique Amps Distribution and kept his job as the designer.

In effect, he handed the business side to another company and went on doing what had interested him from the very start: designing amps.

And making music. In 2014 he played in two bands, Los Peligrosos and The Kings of Outlaw Country, and in the second one he played pedal steel guitar. In 2015 he played lead guitar in the Seattle band The Industry People and recorded the song Rock & Roll Needs a Broom with them. That is the band he is with in the photo at the top of this article. He still plays.

There is a wonderful symmetry in this story.

As a young man Mike heard Eric Clapton’s solo and decided to learn the electric guitar. He bought an amp that kept breaking down. He learned to fix it. Then to modify it. Then to design completely new ones.

About eleven years later Eric Clapton himself ordered an amp from Mike Soldano.

And Soldano never set out to create a new industry standard. He was a guitarist who did not like how the amps of his day sounded.

That is one of the most interesting traits of the early boutique movement: engineers like Soldano were not trying to copy yet another historic model with "Legendary Tone" written on it. They were trying to build the sound they themselves were missing.

And sometimes the whole music industry then lined up for that sound.

On our site, Soldano is represented by the free CatpitAmp plugin and the X88-IR NAM captures.

Photo at the top of the article: Patricia Lockeman-Young, from The Industry People’s Bandcamp page.