ST-9 Super Tube

The ST-9 Super Tube by Maxon, also known as the ST-9 Pro+, is an updated reissue of the 1980's Super Tube Screamer, with a circuit based on the classic OD-9/OD808. It features a dedicated Midrange knob to dial in the amount of mid boost and a Low Boost switch that adds low-end punch, making it suitable for single-coil pickups. The pedal offers switchable 9- or 18-volt operation for increased headroom and improved dynamics.

The ST-9 Pro+ is designed with a 2SK246 jFET buffer for high input impedance and low output impedance into the first Op Amp, a NJM (JRC) 4558D. The pedal also includes a tweakable mid boost, switchable sets of diodes in the feedback loop, and a switchable capacitor to boost bass. It utilizes an NJM2374A Voltage converter to double the 9V input to 18 VDC, providing more clean headroom before the Op Amps distort.

The pedal's features include Mechanical True Bypass switching via a Fujisoku 4PDT switch, and it can be powered by a 9V battery or a Maxon AC adaptor. The ST-9 Pro+ has the following technical specifications:

- Input Impedance: 500K Ohms
- Output Impedance: 10K Ohms or less
- Maximum Gain: 51dB (2.2 kHz)
- Equivalent Input Noise: -115dB or less (IHF-A)
- Control: MID ENHANCE, DRIVE, TONE, LEVEL
- Switch: Bypass/Effect, Voltage Switch (9V/18V), MODE Switch (CLASSIC/LOW BOOST)
- Indicator: Bypass/Effect LED, 9V LED, 18V LED
- Internal Circuit Voltage: 9VDC / 18VDC (DC / DC Converter)
- Power Consumption: 12mA/9VDC, 36mA/18VDC
- Dimensions: 74 (W) x 124 (D) x 54 (H) mm
- Weight: 610g (including battery, excluding AC adaptor)

The ST-9 Super Tube Pro+ is a versatile and powerful distortion pedal suitable for a wide range of playing styles, from bluesy overdrive to heavy distortion.