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Fractal Audio AMP models: SOLO 88 and SOLO X99 (Soldano X88R and X99)


* EDIT: Up-to-date information is available in Yek's Guide to the Fractal Audio Amplifier Models *

SOLO 88 and SOLO 99: based on Soldano X88R and Soldano/Caswell X99

Mike Soldano doesn’t lack self-confidence: “We make the best guitar amplifiers in the world.” He also believes that tube rectifiers are no good, and that Class A/B is the only way to design any amp.

Famous Soldano players include Eric Clapton, EVH, Steve Vai, Warren Hayes, Ian Thornley (Big Wreck), Prince, Steve Lukather, Gary Moore and Mark Knopfler.

The most famous Soldano amp is the SLO-100 head (described in the previous write-up). The X88R and X99 are preamps which provide part of the SLO-100 sound but are different at the same time. The models use the SLO-100’s power amp model.

"Solo 88 RHY is based on an X88R since the rhythm channel of an X99 is identical to an SLO 100. FWIW, I have two X88Rs and the model agrees with both."

"The rhythm channel of an X99 is identical to a SLO 100."​

"Power amp: same as SLO100."
The X88R and X99 are easily recognizable by their purple color. The preamps have Clean, Rhythm and Lead channels, which all have been modeled, except the Rhythm channel on the X99.

The controls are Preamp (gain), Bass, Middle, Treble, Volume, and a Bright switch on the Clean and Rhythm channels.

According to Bob Bradshaw, the X88R was the result of collaboration between Soldano and Bob Bradshaw, and also was the basis for the CAA 3+.

Bob Bradshaw:

“From 1985 to 1990 I toured with Steve Lukather on all the Toto shows. We were taking a lot of equipment to Europe and it got to the point were we needed to scale down and change things a lot. I go well: here we are with this big rack full of amplifiers that we're basically using as preamps. It was a Mesa-Boogie for a clean sound, a Marshall for a crunch sound and a Soldano for a solo sound. We were just using the preamp section of those amps, so I thought, why can't we make a three channel preamp with clean, crunch and overdrive and we'll use power amps that were using anyway. So I went to Mike Soldano and explained him the situation that we needed to scale our rig down to take overseas. Hence the Soldano X-88 R. Which was my concept, Soldano came up with the circuitry and everything, but it was my thing. The amp came out and it was a big hit. $1800 a piece. Soldano sells em to me for $1700. I only make a $100 for each amp I sell myself, it's like, com'on you now. But I own the prototype. In the meantime I start working with John Suhr. John is building great guitars at the same time, he's interested in doing amp work. John was on the eastcoast. The Soldano preamp needed help, it always needed an extra EQ to breathe some life into it. It was a great basic thing, but it needed some top, some bottom. There were things about it that we wanted to change. Mike Soldano was kind of reluctant to make any of these big changes, he had something going and was happy the way things went. (…)”​

The X99 is similar to the X88R, with the addition of MIDI-controlled motorized pots, designed by Tim Caswell.

Caswell Amplificaton:

"Tim teamed up with Soldano Custom Amplification - a California-based amp manufacturer - to design and produce a preamp: the Soldano/Caswell X99 MIDI Motorized Preamp, featuring Tim's innovative system of real-time-controllable motorized knobs."
I wasn't able to find any of the manuals online.

Soldano uses 12" Eminence V12 speakers in its cabinets. We’ve got those as stock cabs: 4x12 Solo V12 (RW).

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Fractal Fanatic
You write that these amps have 6L6 tubes, but I thought they were preamps only, and 6L6 is a power tube? Typo?

Great write-up as always Yek. I really dig the CAA 3+ model, and I will probably stay with that one. I guess these preamps are paired with the SLO100 power amp, whereas the CAA is paired with a VHT power amp. That might make quire a difference.


The Cleansound in the third Video is abolut trademark Steve Lukather. I have to try this, if we can do it with the Axe.


Wow, never saw that thread, and the CAE one. That's a lot of work and knowledge. Nice job!
I'll try the presets for sure.
Wow, never saw that thread, and the CAE one. That's a lot of work and knowledge. Nice job!
I'll try the presets for sure.
this Luke preset is one of the best I've tried.....thanks @guitarnerdswe and @yek
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