The Gotoh SG503 is a style of machine head (a.k.a. tuning peg) installed on a number of Ibanez guitar models. It is manufactured by the G-GOTOH Gut Co., Ltd. in Japan.
The SG503 offers a 1:15 gear ratio. It is available for both 6-inline and 3-on-a-side (L3+R3) headstock configurations. A variety of button shapes are also available, though most Ibanez guitars are equipped with style "07" which is an ovaloid shape with squared off sides. Both locking and non-locking versions are offered.
This machinehead was employed on a variety of Prestige models in the S, SA and SZ series, such as the SA1060Z. For a complete inventory of models using the SG503, see this list.
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Machinehead variations[]
Height adjustable locking posts (H.A.P.)[]
The SG503 is available with height-adjustable posts (H.A.P). This allows the user to adjust individual strings to dial in the oscillation, which contributes to sustain.