Building upon the brand's popular If 6 Was 9 fuzz circuit, the Spanish Castle Dual Fuzz gives players an expanded palette of tweakable fuzz tones, with each side of the circuit having been inspired by the If 6 Was 9's signature sounds. The Spanish Castle's "Fuzz A" is a warm, vintage-voiced fuzz, equipped with silicon transistors and carbon comp resistors, while "Fuzz B" plays its modern counterpart, featuring a tighter voice, metal film resistors, high-gain transistors, and extended bias range for gated and sputtery fuzz tones as well as smoother, more traditional sounds.