Maxon Sonic Distortion SD9

The Maxon Sonic Distortion SD9 is a compact distortion pedal in Maxon's 9 Series, a line RockBoard's PedalPedia calls the "black sheep" of the family¹. It delivers saturated distortion aimed at screaming leads and thick rhythms, with smooth distortion, long sustain and clear articulation². The circuit goes back to 1981, when Susumu Tamura, the designer behind the Tube Screamer, invented the basic SD-9 circuit architecture³.

The pedal is closely associated with Scott Henderson, who used it as his main distortion pedal for 20 years and praised it in strong terms⁴. The standard SD-9 is currently listed as sold out on the maker's product page¹.

What it does and how it is controlled

The SD-9 has a three-knob layout of distortion, tone and level⁵. Maxon describes the pedal as offering "the best characteristics of transistor and op-amp circuits in one compact unit"¹. Vintage Guitar's reviewer characterized it as a higher-gain version of the OD-9 that replaces the drive knob with one for distortion⁶.

The tone knob

The tone control is the part of the stock pedal that draws the most comment. The original Ibanez-era description says the Tone control "allows the artist to modify the distortion with bass or treble boost for exciting new colorations"⁷. In practice, players have found its useful range narrow.

Analog Man's page on the SD9 is blunt about it: the pedal "sounds pretty good stock with the tone knob rolled all the way down, but very little high end," and "when you turn up the tone knob, the low end is decreased and you get a scooped mids sound, which I dont like"⁸. Maxon itself acknowledges the stock pedal's shortcomings, listing "a loss of low-end on high notes and a Tone control that was basically unusable past the 9 o'clock" setting⁹.

For a player buying a stock SD-9, the practical takeaway from these accounts is that the tone knob works best rolled down, and that turning it up trades low end for a scooped-mid character⁸.

Transistors, op-amps and the circuit

The SD-9 circuit uses dual op-amps of the JRC4558 type. Vintage Guitar's reviewer noted the pedal "also employs the JRC chip"⁶¹⁰, and a technical analysis of the SD9M variant describes the circuit as built around dual op-amps, referred to as JRC4558 chips¹⁰. The current production OD-9 from the same series uses the NJM (JRC) 4558D op-amp¹¹. Maxon's own framing is that the pedal blends the characteristics of transistor and op-amp circuits in one unit¹.

How it differs from the OD9

The Maxon SD-9 sits alongside the OD-9 within the 9 Series, and the two are close relatives. Vintage Guitar called the SD-9 "the higher-gain SD-9 Sonic Distortion," describing it as a higher-gain version of the OD-9 with the drive knob replaced by a distortion knob⁶. A build document for the circuit notes the SD9 was designed in the same era as the OD9². Players who want overdrive character stay with the OD-9; players who want more saturation reach for the SD-9.

Where it came from

The SD-9 began life as an Ibanez-branded pedal built by Maxon in Japan. Production of the Ibanez SD-9 Sonic Distortion ran from 1982 to 1984¹²⁷, though sources differ on the exact debut: Aion FX says it first hit stores around 1982, while Guitar World dates the original SD-9 to 1981¹³³. Ibanez's own description from the era says the pedal "expands on the traditional idea of distortion to create a wide new range of possibilities," and General Guitar Gadgets characterizes it as heavier distortion than the Tube Screamer⁷.

JHS Pedals' history of distortion gives the original its due:

The pedal was not reissued until 2002, when Maxon broke off from Ibanez and released the Nine Series under its own name. Aion FX notes the reissue's circuit is identical to the 1980s version aside from true-bypass switching¹³. Ibanez later reissued a modified version, the Ibanez SD9M, from 2012 onward¹². On the JHS YouTube channel, Josh Scott summed up the original's reputation: "the Ibanez SD 9 sonic Distortion kind of in the shadow of the ts9 at all times but it's really really great"¹⁵.

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The Scott Henderson versions

Scott Henderson's long association with the pedal led to a series of signature and updated models. In 2020 Maxon announced the Scott Henderson SD-9SH Sonic Distortion, billed by gearnews as "The best distortion in the world"⁵. It keeps the same three-knob layout of distortion, tone and level as the original, with tweaks developed with Henderson and an additional output level⁵. Guitar World reported the voicing changes included a reduced treble response and lower-mid accentuation¹⁶. The gearnews writer's verdict: "I reckon that this new SD-9SH is probably one to check out. I'm certainly looking forward to hearing one soon"⁵.

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