Eddie uses an MXR 90 phaser on the solo instrumental, "Eruption." Phasers are a type of modulation effect that create a series of peaks and dips in the frequency spectrum, so the sound constantly drifts through a range of tones. The intensity of a phaser effect is user-determined and can range from a mild, sweeping sound to an intense and distinctive fluttering.
Distortion is a classic rock effect that characterizes the genre. What is distinctive about Eddie's use of distortion is that he positions preamp distortion after the phaser in the signal chain. This results in the phased signal being distorted, rather than the distorted signal being phased. There is a noticeable difference in the sonic results and effects placement plays a large part in the tonal outcome. Eddie also uses speaker distortion, for a raw and harsh-sounding effect.
At the start of "Ain't Talkin' 'Bout Love," from the band's self-titled debut, the use of delay is extremely prominent. The riff, which centers around an A minor chord-shape, "bounces" around the speakers as the delay unit creates an intense echo effect. Delay units sample, store and then play back the original guitar sound at a slightly later interval, to create a range of effects including slap-back, echo, filtering and layering.
Flanger is from the same family of effects as phase, but has a wider scope for frequency manipulation. Where a phaser's effect is shallow and brief, a flanger is deep and prolonged. The most prominent example of EVH using flange is at the start of "Why Can't This Be Love?"
Eddie uses a Palmer speaker simulation unit to create a dummy load effect. This effect is created by attenuating the power delivered to the speakers, after the preamp stage of the amplifier. Amplifiers sound different at high volumes, because the power section works harder to generate the increased output. The dummy load effect emulates the sound minus the volume. This is how Eddie achieves speaker distortion.
Although he has this effect in his rig, it is not something that characterizes his tone. Eddie occasionally uses this effect to thicken up the sound of his guitar during solos.
This is a foot-operated expression effect that enhances frequencies bands in the guitar signal, depending on the position of the foot-pedal. Eddie uses the wah effect in an atypical fashion, favoring slow "swells" over rapid, piercing peaks.