Monarch MDI-22 Distortion

The Monarch MDI-22 Distortion is a Japanese-built analog distortion pedal developed in the early 1990s, sharing its circuit and construction with the Aria ADT-1 and several OEM counterparts such as the IMG Stage Line MDI-22, Ken Multi MDI-22, Axe MDT-7, and Sound Lab MDT-7. All of these pedals were produced by the same manufacturer and differ only in branding and minor aesthetic details.

Designed around the well-regarded JRC4558 operational amplifier, the MDI-22 delivers a smooth, responsive distortion character with strong midrange presence and tight bass. This particular pedal has BA4558 chip, that is equivalent to the coveted JRC4558. The tone profile sits between classic overdrive and full distortion, offering touch-sensitive dynamics that respond naturally to playing style and guitar volume. Its gain range spans from warm crunch suitable for rhythm work to thick, saturated drive for solos, making it adaptable across genres such as blues, hard rock, and early metal.

The pedal features a straightforward three-control layout: Level, Tone, and Distortion. Level adjusts the overall output, Tone sculpts the frequency balance from dark and mellow to bright and cutting, and Distortion controls the amount of gain and clipping. Together, they provide a versatile foundation for both transparent boost applications and heavier distortion textures.

Encased in a compact molded plastic chassis, the MDI-22 combines portability with durability. It includes an LED status indicator, a footswitch for bypass control, and operates via 9V battery or standard 9V DC power supply. The pedal's construction and internal design are identical to its sibling models, confirming its shared lineage within the Aria family of effects.

Controls

• Level: Sets overall output volume

• Tone: Adjusts frequency contour from warm to bright

• Distortion: Varies gain and saturation intensity

Connections

• Input: 1/4-inch mono input jack

• Output: 1/4-inch mono output jack

• Power Input: 9V DC center-negative jack

Technical Specifications

• Operational Amplifier: BA4558

• Input Impedance: 300 kOhm

• Output Impedance: 200 Ohm

• Maximum Gain: 50 dB

• S/N Ratio: 85 dB

• Frequency Response: 70 Hz to 5 kHz

• Power Source: 9V battery or 9V DC adapter

• Dimensions: 125 mm (L) x 75 mm (W) x 55 mm (H)

• Weight: 305 g

• Country of Manufacture: Japan

Highlights

• Identical circuitry to the Aria ADT-1 Distortion and other OEM versions such as the Ken Multi MDI-22 and IMG Stage Line MDI-22

• Classic JRC4558-based analog circuit with natural midrange emphasis and smooth clipping

• Wide tonal range covering light overdrive to high-gain distortion

• Simple three-knob layout for intuitive tone shaping

• Lightweight yet robust molded housing ideal for portable use

• A collectible representative of early-1990s Japanese OEM distortion designs