Electro-Harmonix Op-Amp Big Muff Pi Operating Instructions

Op-Amp Big Muff Pi
Congratulations on your purchase of the Op-Amp Big Muff, our faithful re-creation of
the late '70s circuit. The circuitry of the Op-Amp Big Muff – sometimes also referred
to as the IC or V4 Big Muff – differs from the traditional transistor-based Big Muff
circuit in that it uses operational amplifiers (op-amps) to achieve its signature
sustaining distortion sound. With widely-sweeping tone controls and a character all
its own, the Op-Amp Big Muff will surely be a formidable addition to your sonic
arsenal.
OPERATING INSTRUCTIONS
VOLUME Control – Sets the output level
TONE Control – Provides a range of sounds from high treble to deep bass. As you
turn the knob clockwise the treble increases and bass decreases.
TONE Switch – Removes the TONE control from the circuit. This switch has been
improved over the original Op-Amp Big Muff in that the volume remains the same in
both positions.
FUZZ Control – Adjusts the amount of sustain and distortion
Footswitch & Status LED – When the LED is lit, the Big Muff effect is active. When
the LED is off, the Big Muff is in true bypass mode. The Footswitch toggles between
effect and bypass modes.
INPUT Jack – This ¼" jack is the audio input to the Op-Amp Big Muff. The input
impedance presented at this jack is 55 kΩ.
AMP Jack – This ¼" jack is the audio output from the Op-Amp Big Muff. When the
Big Muff is in bypass mode, the AMP jack is connected directly to the INPUT jack.
9V Power Jack – The Op-Amp Big Muff is powered from a 9V battery or you can
use an optional 9VDC AC Adapter capable of delivering at least 25mA to the 9V power
jack, such as the EHX9.6DC-200. The AC Adapter must have a center negative plug.
The battery may be left in or taken out when using an AC Adapter. The Op-Amp Big
Muff has a current draw of approximately 5mA at 9VDC.
We recommend the Electro-Harmonix US96DC-200BI AC Adapter to power
your Op-Amp Big Muff.