Piggy is an overdrive pedal with 3 j-fets arranged in a tube-like manner.
Basically the pedal’s schematic looks like this
Gain Stage I – Bass Control – Gain Stage II – Sag Control – Gain Stage III – Treble Control – Volume
All of the gain stages incorporate hand-selected j-fet transistors which then are tuned for best performance.
Gain knob controls simultaneously Gain Stage I and Gain Stage II ranging from clean boost though overdrive to full range fuzz sounds.
Gain Stage III is used for volume compensation. So you get decent volume levels even when the gain knob is set fully counterclockwise.
Bass control is a passive hpf between first and second gain stage. So less bass means cleaner signal and more bass means more saturated and fuller sound.
Sag knob controls starve of gain stage II – grittier and lofi clockwise, clearer and hifi counterclockwise.
Treble knob is a passive lpf. More highs clockwise, less highs counterclockwise.
Volume knob is your standard overall output control.
Power supply is 9V DC with center negative, 20mA.
Bright red led.