Nine Series Effects Pedals

maxon nine series guitar effects pedalsSince their introduction in the early 1980s, Maxon Nine Series designs have achieved a legendary status with pedal connoisseurs around the globe. The reasons for this are simple - superior sound quality and innovative features that offer a seamless interface between performer and performance. 20 years later this rule still holds true. Now available with improved circuitry including JRC4558 IC chips and True Bypass Switching, Maxon Nine Series effects remain the standard by which all others are judged.

ST-9 Pro Plus Super Tube


More Info

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.

Why Choose Maxon?

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

Tech Talk

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.

Mods & Mends

Classic 808 Mod

Diode Swap Mod


st9 pro plus video 01


Tone Talk - Episode 6
st9 pro plus video 02


Cannibal Corpse - Rob Barrett
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Demo - Live On Stage
st9 pro plus video 04


Phil Caivano of Monster Magnet
st9 pro plus video 05


ST9Pro+ Metal Demo
st9 pro plus video 06


Super Tube Overdrive Pedal Demo
st9 pro plus video 07

Pop Into the Chemist

ST-9 Pro+ Super Tube Demo
st9 pro plus video 08


Gary Holt of Slayer
st9 pro plus video 09

Cannibal Corpse

Gary Holt of Slayer
st9 pro plus video 10

Premier Guitar - Monster Magnet

Rig Rundown with Phil Caivano



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)
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 * All specifications are subject to change for improvement without notice or obligation. All brand names and product names are trademarks or registered trademarks of their respective companies.
  • 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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John commented on 28-Mar-2014 06:25 PM5 out of 5 stars
Love the pedal. Sounds amazing with my Fargen Olde 800 MK II amp. Powering as per the tech talk above, but can this also be powered with an 18v adapter? (Perhaps could be mentioned in the tech talk.)
ST-9 Pro Plus Super Tube
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