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Maxon ST-9 Pro+

Regular price $239.00

Shipping calculated at checkout

Maxon Super Tube Pro Plus 

Bigger, Badder, Bolder – these are the best three words to describe the ST-9 Pro+ Super Tube.  The latest and possibly last incarnation of Maxon’s legendary 808, the ST-9 features more output, more gain, and more tonal options for the player who simply needs – well, MORE.

Starting with a circuit loosely based on the classic 808 architecture, the ST-9 adds a Mid Enhance knob to control the amount of midrange boost.  This knob functions similarly to an amp’s presence control, boosting perceived volume and gain as it’s turned up.

You may be wondering why an 808-style pedal would need more presence – allow us to introduce you to the ST-9’s Low Boost switch.

The Low Boost switch is the ST-9’s secret weapon – This unassuming switch completely changes the character of the pedal, adding beefy low end and increased saturation via a LP filter and an alternate set of clipping diodes.

If this wasn’t enough, the ST-9 also offers 9- or 18-volt operation via an internal charge pump.  Run at 9 for the classic 808 sound and feel or switch to 18 for increased headroom, improved dynamics, and a bigger, chunkier tone to the overdrive.

From bluesy overdrive to diabolical dirt box, the ST-9 is a devilishly diverse pedal that can punish a clean amp or turn a dirty amp into a wall of doom.

The OD808 re-imagined with increased output level, additional saturation and a more diverse palette of tonal options.


Input signal goes to a 2SK246 jFET buffer that provides a high input impedance and low output impedance into the 1st Op Amp, a NJM (JRC) 4558D. This 1st 4558 is set up as a tweakable mid boost, with a potentiometer controlling the gain of the boost.  The signal goes from the mid boost Op Amp to the second clipping Op Amp, which is set up for a 10 to 110x gain with switchable sets of diodes in the feedback loop and a switchable capacitor to boost bass.

After the clipping Op Amp the signal is routed to an 808-style tone control and unity gain amplifier, after which the signal is passed through a volume potentiometer, another unity gain amplifier (to provide low output impedance) and then the true bypass switch.  The use of these unity gain amplifiers helps to preserve high end in the signal which can be lost when passing through the volume control.

The ST9 Pro+ uses an NJM2374A Voltage converter to double the 9V input to 18 VDC, providing more clean headroom before the Op Amps distort.  The ST9 circuit is switchable between 9 and 18VDC via an internal switch.

The ST-9 Pro+ features Mechanical True Bypass switching via a Fujisoku 4PDT switch – the input of circuit is switched to ground when bypassed.

NOTE ON POWERING THE ST-9 Pro+ - this pedal’s voltage regulator IC requires a high inrush current of approximately 2000 mA upon startup.  When using with a Power Brick such as the Voodoo Labs Pedal Power 2+, this pedal should be connected to a high current power jack when possible.

If it is not possible to connect to a high current jack, you can power the ST-9 Pro+ by leaving a battery in the pedal.  Upon initial start-up, unplug the external DC power input cable, engage the pedal, and then plug the DC power input cable back in – the pedal will now power up normally off the external power supply until you power down your pedalboard.

Input Impedance: 500K Ohms

Output Impedance: 10K Ohms or less

Maximum Gain: 51dB (2.2 kHz)

Equivalent Input Noise: -115dB or less (IHF-A)


Bypass/Effect, Voltage Switch (9V/18V)

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

Power Supply: 6F22 / 6LR6 9V battery x 1 or Maxon AC adaptor

Standard Accessory: AC adaptor AC2009, user's guide

Battery life:
9VDC manganese battery 26 hours @ 25 degrees C (Panasonic 6F22NB)
9VDC alkaline battery 48 hours @ 25 degrees C (Panasonic 6LR61G)
18VDC manganese battery 2 hours @ 25 degrees C (Panasonic 6F22NB)
18VDC alkaline battery 8 hours @ 25 degress C (Panasonic 6LR61G)
Option: AC adaptor (Maxon AC210N)* OdB = 0.775Vrms


  • Updated Reissue of 1980’s Super Tube Screamer
  • Circuit Based on classic OD-9/OD808
  • Dedicated Midrange knob to dial in amount of mid boost
  • Low Boost Switch adds low end punch – great for single coils
  • 9-volt or 18-volt regulated operation (switchable)
  • True Bypass Switching
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