Cry Baby
An inductor-based bandpass filter with the treadle sweeping its centre.
A resonant peak, moved by foot
An inductor and a variable resistor make a bandpass filter with enough resonance to have a real peak. Rocking the treadle slides that peak across the spectrum, and the three curves here are three treadle positions rather than three pedals.
- Heel
- Middle
- Toe
Drawn to illustrate the description above. Horizontal axis: frequency, low to high.
What the circuit does
An inductor and a variable resistor form a resonant bandpass filter. Rocking the treadle moves the centre frequency across roughly the 400 Hz to 2 kHz range, with enough resonance at the peak that the filter is heard as a shape rather than as an EQ change.
What to listen for
A vowel sound, because that sweep is close to what a mouth does to a formant. Left parked at one position it stops being an effect and becomes a fixed midrange voice, which is the less obvious half of what it is good for.
Where it goes
The wah and filter slot
Early, so it shapes the plain guitar and the drive after it responds to that shape. Put a wah after a distortion instead and the sweep sounds flatter, because the distortion has already flattened the dynamics the filter would have moved through.
Controls
- Treadle