The MXR Micro Amp (M133) is an op-amp boost pedal released in 1978. It has a single volume control and offers 26 dB of boost, meant to add volume or distortion, depending on where it sits in the signal chain, without colouring the tone. It has become perhaps the most commonly used boost pedal on the market.
The MXR Flanger is a guitar flanger pedal. No technical specifications are available. It belongs in the category of flangers for guitar. That is all the material confirms.
The MXR M126 Flanger/Doubler is a two-space analog rack unit with front-panel 1/4" TRS I/O. It gives players manual, sweep width, sweep speed, mix, and regen knobs plus mode and bypass/invert buttons. It delivers a thick flanging sound and fulfils its synthetic doubling function as advertised. It has no stereo I/O, no expression input, no tap tempo, and no presets. No verified recordings or users are cited. Studio engineers needing fixed, tactile analog flanging or doubling should consider it. Live performers, modular users, and those requiring stereo or foot control should not.
The MXR Distortion + is a 1974 distortion pedal using a single op-amp and germanium diodes. It has Output and Distortion controls only. Increasing Distortion raises both clipping and treble. It was one of MXR’s earliest original pedals, released shortly after the Phase 90. It later appeared in the Series 2000 line in 1982.
The MXR Phase 90 is a phaser effects pedal introduced in 1972, the first pedal sold by MXR. It features one knob (Speed), an orange enclosure, and evolved logo designs (script then block). Production ceased in 1984 when MXR went bankrupt. Dunlop resumed production with added features: an LED and optional AC power supply. Pre-1981 units lacked LEDs, A/C adaptor jacks, and true-bypass switching. It was used on the first two Van Halen albums.
The MXR Dyna Comp is a guitar compressor pedal introduced in the 1970s. It has two controls: Sensitivity and Output. It produces a non-tone-neutral, colour-rich compression effect. It became a Nashville standard. It smooths out volume differences between notes, especially in chicken picking. It was one of the six original pedals in the MXR Series 2000 line.