Ibanez STL Super Tube

The Ibanez STL Super Tube is a four-knob distortion pedal that Ibanez built in Japan in 1985 as part of its Master Series L lineup. Under the name it is a Tube Screamer circuit wearing different clothes: as Premier Guitar put it in its Tube Screamer history, it is "Not officially a Tube screamer, but uses a Tube Screamer circuit with a 2-band EQ"¹. Analog Mike Piera of Analog Man describes it in the same terms, calling it "like a 4 knob tube screamer"².

What separates the STL from a standard Tube Screamer is that extra knob. Where the classic TS circuit gives you level, tone and drive, the STL adds a midrange control, and where that control sits in the signal path is the pedal's defining trait: on the related ST-9 Super Tube Screamer the MIDS control works before the clipping stage, while on the STL it comes after the clipping stage². That placement means the midrange boost shapes the distorted signal rather than pushing the clipper harder, which is the practical difference between the two circuits for a player comparing them.

A four-knob Tube Screamer-style distortion

The STL arrived in the Master Series L, a series Ibanez built for only about a year. Piera notes that "This series was only made in about 1985"², and the series had no Tube Screamer in its official lineup, which is why the STL carries the Super Tube name rather than the Screamer badge. Premier Guitar describes it as "a 4-knob affair with a Tube Screamer circuit and a 2-band EQ"¹.

The four knobs break down like this:

The closest relative is the ST-9 Super Tube Screamer, sold in the 9 Series. TONEHOME calls the ST9 "the culmination of the Tubescreamer"⁴², and Piera describes both pedals as "like a Tube Screamer with an added MIDS control, which is before clipping on the ST-9 and after the clipping s[tage in the STL]"². The ST-9 itself is a different kind of rare: Aion FX notes it "was only made in very small quantities, and only sold in Europe between 1983 and 1984"⁵. Premier Guitar calls the STL "similar to the rare (and very valuable) European ST-9 Super Tube Screamer that was never released in the US"¹.

Inside the circuit

The STL's board follows the family pattern of the era. TONEHOME describes its PCB as similar to the SM9 Super Metal, built around two JRC4558D op amps, the same dual op amp that runs the classic Tube Screamer³. The rest of the signal path is Tube Screamer topology: a buffer, a clipping stage, and tone shaping, with the STL's midrange control sitting after the clipping stage rather than before it as on the ST-9².

The DIY community has documented the circuit closely. Guitar FX Layouts published a vero and tagboard layout for the STL in 2013, and the builders who worked through it left useful notes on the original parts⁶:

• The original schematic uses a 2SK30 FET, and a BF244A can be substituted for it, but not a 2N5457 even with source and gate flipped⁶
• Ceramic or polyester capacitors are recommended over tantalums for the 1µ caps, because there is voltage on both sides of each one⁶
• On the original schematic, D7 is a W03C⁶

The layout also makes the clipping diodes easy to reach, which the blog's author pointed to as a modding opportunity: "the clipping diodes are placed neatly where you can easily take them on the switch and have your way with them"⁶. The suggested approach there is a three-position two-pole switch, with the middle position as a diode lift, one end running four 1N4148s (two in series, two of those in parallel for more volume), and the other end 2 or 4 1N4001s or LEDs⁶.

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