Finding a custom replacement wheel requires precise measurements. Many keyboard owners purchase standard guitar or amplifier knobs only to find they sit too high, rub against the keyboard frame, or wobble uncontrollably. The AULA F75 features a 6mm D-shaped shaft (flatted shaft) with an exposed shaft height of roughly 11.5mm from the PCB surface to the tip.
The outer diameter of the top-case cutout measures 20.5mm. Any replacement knob exceeding 19.8mm in outside diameter will scrape the sides of the case opening during rotation. The table below outlines real-world test results across popular replacement knob styles.
| Knob Type & Material | Shaft Mount Style | Clearance & Fitment Result |
|---|---|---|
| Stock AULA Factory Cap (Aluminum/ABS) | Integrated 6mm D-Sleeve | Flush fit; 1.2mm perimeter gap; zero case scraping. |
| Guitar Knurled Dome Knob (Solid Brass/Steel) | Side Set-Screw (Round 6.0mm) | Fits if diameter is under 19mm; screw must hit flat D-side to prevent eccentric spin. |
| Universal Audio Fluted Knob (Bakelite) | 18-Tooth Splined / Split Shaft | Incompatible; splines strip over smooth D-shaft; requires brass adapter sleeve. |
| Custom CNC Low-Profile Cap (Anodized Aluminum) | M3 Grub Screw / 6mm Bore | Ideal fit; tight tolerances; eliminates vertical play when seated 1mm above top bezel. |
When installing aftermarket knobs with side-locking grub screws, align the screw precisely against the flat face of the D-shaft. Tightening down against the curved side pushes the knob off-axis, making it turn unevenly and grind into the chassis wall.
