Dunlop MXR M400 Turbo Pedałowy tuner

Strobe Tuning Precision for the Pedalboard

The MXR M400 Turbo Tuner brings the gold standard in strobe tuning to a compact stompbox. Built around the core engine of Sonic Research's original Turbo Tuner, this pedal delivers tour-grade precision. The pattern in the LED strobe ring rotates in real time as you turn the tuning peg—sharp notes spin right, flat notes spin left, and the rotation slows as you close in on pitch. When the strobe is just creeping along, you're within a fraction of a cent.

What Sets the M400 Apart

Instead of a needle-style display, this unit uses a true strobe display with zero latency that keeps up no matter how fast you turn the tuning pegs. Four brightness levels keep the display readable in any lighting. A USB-C port supports firmware updates and Dunlop's editor software.

Tuning Modes and Preset Flexibility

Chromatic mode covers C0 to C8, while Guitar and Bass presets track open strings and display the string number. Three additional presets come pre-loaded with standard guitar, drop D, and 6-string bass tunings. Each preset can be reprogrammed for open tunings with up to 12 strings or custom temperaments with ±50-cent offsets in 0.1-cent steps.

• Type: Chromatic strobe pedal tuner
• Accuracy: ±0.02 cents — precise enough for setting intonation
• A4 Reference: 300.0–599.9 Hz, stored per preset

Power and Connectivity

Runs on a 9V DC adapter or 9V battery. The 9V DC output daisy-chains power to another pedal.

• Power: 9V DC adapter or 9V battery
• USB-C: Editor software and firmware updates

Bypass Configuration

Relay-switched true bypass mutes output for silent tuning. An internal toggle selects buffered bypass for long cable runs, with three submodes: Default, Passthrough, and Monitor. The enclosure measures 112 × 61 × 48 mm and weighs 192 g without battery.

• Bypass: Switchable true bypass or buffered
• Buffered Submodes: Default, Passthrough, Monitor
• Dimensions: 112 × 61 × 48 mm