Maxon ST-9 Pro+ Super Tube overdrive

The ST9Pro+ was developed based on the legendary overdrive Maxon ST9, which was released in the 80s and still well-known even after it was discontinued. The ST9 was reborn as ST9Pro+ with new circuitry, creating powerful, heavy, fat sound like a stack amp with midrange boost control. With newly added low boost circuitry, more powerful distortion is selectable. It operates under 9V but an internal switch can be set at 18V, increasing dynamic headroom, stabilizing high-quality sound and reducing significantly all background noise.

• ST9Pro+ was developed based on the legendary overdrive Maxon ST9, which was released in the 80s and still well-known even after it was discontinued. ST9 was reborn as ST9Pro+ with new circuitry.
• ST9Pro+ creates powerful, heavy, fat sound like a stack amp with midrange boost control.
  Wide range of setting, such as a booster, blues and hard rock, is available.
• With newly added selectable diode clip circuitry and low-end boost circuitry,
  more powerful distortion and low-end boost are available.
• Operating voltage (9V or 18V mode) is switchable via an internal slide switch accessible through
  the unit’s battery compartment.
  In new power-saving circuitry for ST9Pro+, DC to DC converter only operates at 18V mode.
  When 9V mode is selected, DC to DC converter does not operate, and ST9Pro+ operates with battery or
  AC adaptor directly.
  There is no power consumption for DC to DC converter, which makes battery life last longer.
• ST9Pro+ has increased dynamic headroom with internal operating voltage set at 18V.
  Stable high-quality sound is available as unintentionally-generated distortion is significantly reduced.
• TBS (True Bypass Switching) using 4PDT mechanical switch lets your instrument’s signal pass
  through a non-electronic bypass line when the effect is disengaged, feeding your amplifier with direct,
  unaltered signal from your instrument.
  No tone changes when the effect is engaged as signal does not pass through electronic switching circuitry.
  This TBS gains enormous popularity among artists.
• Easy-access, tool-free battery compartment.
• MADE IN JAPAN

Specs:

• Input Impedance 500k ohms
• Output Impedance 10k ohms or less
• Maximum Gain 51dB（2.2kHz)
• 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 Supply 6F22/6LF22 9V battery x 1 or Maxon AC adaptor
• Power Consumption 12mA/9VDC,36mA/18VDC
• Battery Life 9VDC manganese battery 26 hours 25℃（Panasonic 6F22NB） alkaline battery 48 hours 25℃（Panasonic 6LR61G) 18VDC manganese battery 2 hours 25℃（Panasonic 6F22NB） alkaline battery 8 hours 25℃（Panasonic 6LR61G）
• Dimensions 74(W)×124(D)×54(H)mm
• Weight 610g（including battery）
• Accessory 6F22 9V battery x 1, operating manual