The FX files: Dunlop Cry Baby

The most famous wah pedal in the world, the Cry Baby has been used by every guitarist from Hendrix to Hammett.

Named after the Vox Cry Baby pedal it imitated, the Dunlop Cry Baby became synonymous with ‘wah pedal’. Although there have been many versions and countless classic tones created with it, the core circuit has remained largely stable since the 60s.

The wah was originally developed to emulate the sound of a muted trumpet

The wah was originally developed to emulate the sound of a muted trumpet, and when combined with a rocking treadle, allowed for a hugely expressive range of filter sounds to be created.

An early and progressive adopter was a young guitar virtuoso named Jimi Hendrix, who had already seen the brass parallels with the electric guitar when he dubbed it the “public saxophone”. Whether filtering feedback and sustained notes through a wall of sound or adding percussive clicks to the opening of Voodoo Child, Hendrix remains the wah master.

At the core of the circuit is an active bandpass filter, created using an inductor. The filter is centred at around 750Hz, where it delivers 18dB of boost, and attenuates out-of-band frequencies. On the original GCB-95 model, the sweep available from the treadle was from about 450Hz to 1600Hz. Later developments, such as the bass version, change the frequency range - although it’s also relatively simple to add additional boost or alter the Q - that is, the severity of the curve - of the filter.

Used as a variable filter, rather than as a tool to accent individual notes, the Dunlop Cry Baby has a distinctly different character. By rapidly sweeping the treadle, a ‘waka’ sound can be generated as the filter brings out treble in the guitar, particularly if the guitarist is using pick scratches. This classic sound is pervasive across the funk genre, and it also features in a number of iconic police show soundtracks too.

Dry your eyes

The true beauty of the Cry Baby is that it has only one real control - the potentiometer that is varied by your foot moving the treadle. Putting your toe down or up sweeps the centre frequency of the filter band.

Frequencies outside of this band are attenuated, and frequencies within it are not only retained, but actively boosted. It’s this selective boosting or rejection of frequencies, combined with the dynamic ability to rapidly change them, that gives this famous wah pedal its instantly recognisable sound.

Under the influence

Classic tones

This isn’t a signature sound for Matt Bellamy, but it crops up fairly often in breakdowns and drops. Here, the pedal is on, and completely toe-down for a radical filter effect in the intro - to up the ante, there’s a fuzz in front. Just before the band kicks in, turn the pedal off and let your fuzz come through unfiltered.

Dire Straits - Money For Nothing

Although the original pedal used on this track was reportedly a Morley, the parked, partly-open wah sound in the intro of this song is probably the most iconic non-standard use of a wah pedal in rock music, and instantly recognisable. Turn the pedal on and pull it back until you hear that sign.

Joe Satriani - Surfing With The Alien

Before his Vox signature, Joe used a number of Cry Baby pedals over the years to get his signature expressive lead tone. By using the wah, he could drag vowel-like sounds out of his instrument while slower sweeps paired with fast tapping deliver a filter or phase-shifter like sound. These techniques are all over this track.

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