Ghosts in the Machine: Inside creation of the Soundblox Classic Distortion

Referred to as the “best distortion box ever” by both vintage tone champion Adrian Belew of King Crimson and neo-shredder Herman Li of DragonForce, the newly released Soundblox Classic Distortion by Source Audio is showing that analog soul can be captured on a digital chip.

A veritable Ghost Trap a la Ghostbusters, the Soundblox Classic Distortion houses eleven recaptured spirits of prevalent distortion sounds resulting from a five-year listening study of stomp boxes and tube amps. Sounds from the Big Muff Pi, Fulltone Distortion Pro, Tone Bender, Fuzz Face, ProCo Rat and Octavia can all be selected at the turn of a knob on the Soundblox Classic and then further tweaked by a graphic equalizer, two drive knobs, midrange knob and an output knob.

In addition, Source Audio has provided the option of tweaking the old sounds even further via an expression pedal morphing function, MIDI input connection and a jack for the Hot Hand motion-sensing controller.

Source Audio, now in it’s fifth year as a company, is a true nod to the marriage of music and technology. Having formed as a spin-off from the well-known semi-conductor company Analog Devices, they were able to request a customized state-of-the-art Digital Signal Processor, the SA601 chip, to pursue their music-centric interests. The two sets of ears in the listening study, VP of Engineering Jesse Remignanti (former audio systems and software engineer at Analog Devices) and Chief Scientist Bob Chidlaw (former senior engineer at Kurzweil Music) sat down to discuss the listening study, the process of creating the Soundblox Classic Distortion and a few other topics for the audiophile at home.

The need for a pedal that housed multiple quality distortion tones was clear to Jesse Remignanti, a veteran guitarist of the New England music scene. One of his challenges for the creation of the Soundblox Classic Distortion was to design an interface that could work seamlessly on-stage. He muses, “I’ve seen some guys who have anywhere from six to ten pedals on their board which are just distortion…jumping from one pedal to the other and doing a toe-tapping dance to get one sound to another sound.” He continues, “It’s easier to just have it called up on a preset or use the expression pedal. It’s useful for anyone from the pro musician to the guy who’s doing cover tunes and needs a different sound because they’re doing Metallica and then The Cars.”

For Chidlaw, a collector of tube amps, the challenge was to create digital sounds from scratch that matched his standards for analog sounds, which were quite high at the beginning of the project. “When I started at Source Audio, I was a real tube amp snob” states Chidlaw matter-of-factly. “The only distortion I would use was real distortion from a tube amp. I would sometimes modify amps to get more gain. Turning up the gain on a Marshall JCM-800 was one of my little moves.”

To truly capture some of the most notable distortion sounds in the fuzz pantheon, Bob and Jesse would have to explore the world of stomp boxes and as they dug deeper, Chidlaw’s tastes began to open up. “I had built solid-state distortion devices before. I really had just rejected them all by this point 5 years ago.” He reflects, “But then we bought a distortion pedal, the Fulltone Distortion Pro and I thought, ‘wow, this actually does sound quite nice.’ Then when we really started getting into the Classic Distortion we started acquiring a lot more pedals. I personally bought far too many for my growing collection. I really came to see the charm in solid-state distortions. It really gives you something that a vaccum tube can’t. You can’t get that sound from a vacuum tube amplifier. It can’t be done.”

In mapping the digital sounds to be placed in the Soundblox Classic Distortion, Chidlaw had to create each algorithm from the ground up, attempting to capture the essence of each distortion tone. “An algorithm is a recipe of how the sound is processed…There’s a lot of trial and error; a lot of tweaking… I just have to use my ears to try to compare what the digital system is doing with what the real analog pedal is doing.”

He continues, “You can’t really point to a sound as it goes by. Try to hear just what it is that makes a particular fuzz have it’s own sound. What is in the sound? All you can say is ‘doesn’t that sound kind of harsh in the high end?’ and maybe it does or maybe it doesn’t strike you that way… If you’re making something analog, you can say ‘I’ll use some of these transistors that were very cheap back in the day when this thing was built’ but what is the digital signal processing equivalent of a cheap transistor? Not at all obvious…”


Classic Distortions waiting for shipment

The timing of the release for the Soundblox Classic Distortion is fairly fortuitous, coming at a time of heightened expectations for musicians. As modern music fans gain more access to more music across a longer timeline, they seem to gravitate toward either the eccentric or the tried and true. A look at the Billboard Top Ten shows a reissue of Exile on Main Street by the Rolling Stones alongside the likes of Lady Gaga and LCD Soundsystem.


The aim of the Soundblox Classic Distortion is a near precise match for the needs of the modern performer in that it can call up the guitar tone from The Rolling Stones’ ‘Satisfaction’ in one moment and then in the next, it can create a never-before-heard sound.

“It gives you some really interesting effects” explains Remignanti, “because you could get an in-between sound from two completely different pedals. You could switch from the Rat Tone to the Tube Drive or something just by rocking the expression pedal.”

Chidlaw adds, “You can get some more bizarre things happening in the middle of those morphs. You could say there is only twelve selector positions on the Classic Distortion, but if you use the morph control, you’ve really got hundreds of more possible selector positions by just, sort of, freezing the morph. Sixty percent of the way between this and this and you’ve got this new sound that’s in there.”

The versatility of the Classic Distortion can be traced back to that signature chip, the SA601 Digital Signal Processor. The power of the chip allowed the Source Audio engineers to push the pedal into new territories for a distortion stompbox. When asked about the graphic equalizer, another of the pedals unique features, Remignanti says simply “We had enough room in the processing and in the interface to add a seven-band EQ and it’s programmable for each preset. You could have the same distortion effect with three different EQ settings and get totally different sounds out of it. So, it’s a very nice, flexible feature…[It’s] not something commonly seen on distortion pedals.”

A collection of circuit boards used for Source Audio pedals

Matching the considerable uniqueness of the sounds, the aesthetic and layout of the Soundblox Classic Distortion have a simple and modern feel. Remignanti explains, “Our goal with the overall design was to make them simple in terms of the interface and the overall appearance but also modern looking. We tried not buy into the whole retro thing in our main design philosophy for the housings and the look of the pedals. [As for] the interface, we tried to keep it to as low a number of knobs and controls as possible, but still allow the user to get a lot of features and a lot of different sounds.”

For more information on the Soundblox Classic Distortion, please visit:


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