The MXR Custom Shop Script Phase 90 LED is a phaser from MXR's Custom Shop line that reissues the original script-logo Phase 90 with two modern additions: an on/off status LED and an AC power jack. MXR describes it as bringing back "the headroom and clarity of the original, along with its ultra warm and smooth phasing and reduced midrange swell," and it comes dressed in the original smooth orange paint job and script logo1. For players, that means a single-knob vintage-style phaser that can sit on a powered pedalboard without giving up the script-era voicing.
What it does
The Script Phase 90 is a one-control phaser: the footswitch toggles the effect on and off, with a red LED showing the status, and the speed knob sets the rate of the phase shift3. MXR positions the script voicing against the later block-logo Phase 90: the original script version, available from the company's inception to the late '70s, "practically defined the classic phase shift," and the Custom Shop reissue is built to recall that earlier character, with more headroom, a warm and smooth phase sweep, and less midrange swell than the block version12.
Power and practical details
Power is straightforward, and the additions are what make the pedal board-friendly:
- One 9-volt battery, fitted after removing the bottom plate13
- A Dunlop ECB003 9-volt adapter (the manual also names the ECB003E)13
- A Dunlop DC Brick or Iso-Brick power supply13
- Runs on 9 volts DC3
The LED and AC power jack are the practical difference from the vintage pedal, which had neither13.
The LED version is model CSP101CL. Dunlop's manual for the Script Phase 90 carries the model number CSP101SL and describes the same AC power jack and on/off status LED, so the two designations refer to closely related script-logo reissues23.
History and circuit lineage
The script Phase 90 dates back to MXR's early years: the original script-logo version was available from the company's inception to the late '70s1. Later Phase 90s differ internally. General Guitar Gadgets notes that "There is an R15 resistor that is in some of the later Phase 90's," one of the changes that separates block-era units from the script circuit4.
The reissue's exact lineage is worth knowing if you care about circuit detail. GuitarPCB's analysis of the Phase 90 argues that the Custom Shop script reissue "is a regular '75 block model in a script-like case, actually the same EVH circuit, with the 24K resistor missing"5. That is a technical reading rather than MXR's own description, but it explains why players who open these pedals up sometimes find block-era parts inside a script-painted box. For DIY builders, the Guitar FX Layouts project for a Phase 90 with a script switch notes that "to make it a stock script you would just omit the switch and the 22k resistor," a useful reference point for anyone tracing the script voicing to specific components6.
How it compares
Within MXR's own range, the Script Phase 90 LED sits as the full-size Custom Shop script reissue. Players who want more options in one box can look at the MXR Custom Shop Phase 99, and the wider field of one-knob and multi-mode phasers is covered on the site's phaser pedals page. What the Script Phase 90 LED offers specifically is the script voicing with modern power conveniences, in the orange script-logo enclosure1.
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Questions
Does the MXR Custom Shop Script Phase 90 LED run on a battery?
Yes. Dunlop's product page says the pedal can be powered by a 9-volt battery, and the manual for the Script Phase 90 specifies one 9-volt battery, installed after removing the bottom plate. It can also run from a Dunlop ECB003 9-volt adapter or a DC Brick or Iso-Brick power supply.
What adapter does the Script Phase 90 LED use?
The manual lists a 9-volt AC adapter such as the Dunlop ECB003 or ECB003E, or a DC Brick power supply. The product page also names the Dunlop ECB003 9-volt adapter and the DC Brick and Iso-Brick power supplies. The pedal runs on 9 volts DC.
What is the difference between the Script Phase 90 LED and the original script Phase 90?
The reissue adds an on/off status LED and an AC power jack, which the original never had, and MXR says it brings back the headroom and clarity of the original along with its ultra warm and smooth phasing and reduced midrange swell. One independent circuit analysis argues the reissue is built on a later block-model circuit rather than a literal copy of the vintage script unit.
Does the Script Phase 90 LED have an LED indicator?
Yes. The LED is part of what separates this version from the vintage original: the product page describes it as the script logo reissue with an LED and AC power jack, and the manual describes a red LED that indicates when the effect is on.
What is the model number of the Script Phase 90 LED?
The LED version carries the model number CSP101CL, listed as CSP101CL Script Phase 90 LED. The related Script Phase 90 without the LED appears as CSP101SL in Dunlop's manual.
Sources (6)
- MXR® SCRIPT PHASE 90, Dunlop (jimdunlop.com)
- CSP101CL Script Phase 90 LED by MXR, RockBoard PedalPedia, 2026
- CSP101SL.pdf, Jim Dunlop, 2019
- MXR™ Phase 90™ Clone Kit: Script Logo Phaser, Matched JFETs, General Guitar Gadgets, 2014-05-18
- MXR Phase 90 Analysis, GuitarPCB
- Guitar FX Layouts: MXR Phase 90 with Script Switch, tagboardeffects.blogspot.com (Guitar FX Layouts), 2023-11-22
