Ibanez SD-9 Sonic Distortion

The Ibanez SD-9 Sonic Distortion is an analog distortion pedal made in Japan from 1982 to 1984, part of the same 9 Series as the TS9 Tube Screamer. Where the TS9 is an overdrive, the SD9 is a full distortion: more gain, a thicker and more saturated sound, and a tone control that scoops the midrange rather than boosting it. Ibanez describes it as a pedal that "expands on the traditional idea of distortion to create a wide new range of possibilities"¹²³.

The SD9 was discontinued in 1985 along with the rest of the 9 Series, and originals are now collectible, with Tonehome rating collectibility as high and availability as good²⁴. It has lived on through reissues: the Ibanez SD9M since 2012, and the Maxon SD-9 from 2002.

A heavier, mid-scooped cousin of the TS9

The SD9 sits in the TS9's shadow, but players who know it tend to rate it highly. On JHS Pedals' history of distortion, Josh Scott called it "the Ibanez SD 9 sonic Distortion kind of in the shadow of the ts9 at all times but it's really really great"⁵. JHS's written history gives it credit as "the TS9's younger brother"⁶.

Analog Man's take on the sound: "An SD-9 is sort of like a TS-9 designed for distortion, with more hair and a a thicker, more saturated distortion sound" that the site describes as great for leads or thick rhythm⁷. General Guitar Gadgets sums up the family difference simply: heavier distortion than the Tube Screamer⁸.

The two pedals share a platform but differ in the details that matter:

On That Pedal Show, the comparison came down to feel: the TS9 was described as "a bit more compressed" and smoother next to the SD9's character¹¹.

The controls: Distortion, Tone and Level

Three knobs, in the classic 9 Series layout¹:

The Tone control is where the SD9 most departs from its sibling. Aion FX's circuit analysis measured the result as a mid-scoop between 234 Hz and 867 Hz⁴¹, the opposite of the Tube Screamer's famous midrange push. For a player, that means the SD9 leans darker and chunkier through the middle rather than cutting through a mix the way a TS9 does.

How the circuit works

The signal path follows the 9 Series template: input buffer, adjustable gain boost, clipping diodes, tone control, then volume and output buffer⁴.

The distortion itself comes from diode-to-ground hard clipping using back-to-back 1N914 diodes, which clip the signal to around 0.6V on both sides of the waveform⁴. The gain stage feeding those diodes runs from a gain of 71 at minimum Drive to 603 at maximum⁴, which is why the pedal gets genuinely saturated rather than just breaking up.

The circuit also includes an input buffer ahead of the amplifying stages, with D3 serving as a polarity protection diode (a 1N5817 in the popular DIY layout; any Schottky or 1N400X series diode works in an original unit except a zener)⁹.

Why the SD9 is quiet at full volume

The SD9's best-known quirk is its low maximum output. Aion FX calls it "perhaps a design flaw that there's no gain recovery section in the original pedal," which limits the available output volume⁴¹. Because the clipping diodes clamp the signal to about 0.6V, the Level control simply cannot push the pedal much louder than that.

The known fix, documented by Aion FX: adding a BAT46 or germanium diode (0.3V forward voltage) in series with each 1N914 increases the available volume by half, and stacking two 1N914s doubles it⁴. The later SD9M took a different route, adding extra op-amp gain stages not found in the original, which helps the volume issue but does not sound the same as an original SD9⁴.

Power and bypass

The SD9 runs on 9V DC, center negative, drawing 8mA¹. It is an analog circuit¹.

History and versions

The SD-9 first hit stores around 1982 (Aion FX also cites 1983 as a date), was produced in Japan through 1984, and was discontinued in 1985 with the rest of the 9 Series due to poor sales²⁴. Its designer was Susumu Tamura, the same engineer behind the Tube Screamer; Guitar World's Paul Riario calls the SD-9 "also a Tamura original"¹³.

The pedal's later life:

• 2002: Maxon, which had built the original pedals and then broke off from Ibanez, reissued the SD-9 in its Nine Series with a circuit identical to the 1980s version aside from true-bypass switching⁴¹⁴.
• 2012 to present: Ibanez reissued it as the SD9M, a modified version with added gain stages²⁴.
• 2020: Maxon released the Scott Henderson SD-9SH, a version with tweaks developed with Henderson and an additional output level control¹⁵.

Players associated with the pedal include Michael Landau, who That Pedal Show describes as having a long-term relationship with the Ibanez/Maxon SD9¹⁶. A DIY builder reporting on the SD9M circuit called it "a true tool for hard rock. Power chords, single note and great sustain with very high gain without to be muddy"⁹.

Guitar World's Paul Riario, reviewing a related pedal, still held the original in high regard: "I still hold fast that the SD-9 is a great pedal with a distinct distortion unlike any other, despite its limitations," describing its overall character as warmly overdriven with scooped mids and borderline fuzzy at its peak¹³.

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