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.