The DOD FX20B Stereo Phaser is a discontinued six-stage phaser from DOD's FX series. As the name says, it is a stereo pedal, and its six stages give it what Subdecay's Brian Marshall calls a wetter sound than any four-stage phaser. Marshall, who wrote a retrospective of the pedal in April 2017 as the first entry in his Effects Closet series, admits to "an unhealthy affection" for it, but the page that follows is honest about its flaws too: a bypass switch he calls sketchy, and an input impedance well below what DOD claimed.1
Where it came from
The FX20B belongs to DOD's FX series. Marshall traces the line's design language: the early designs resembled MXR offerings, and by the early 1980s DOD was taking more "inspiration" from Boss in both external aesthetics and functionality. The pedal itself also carried a naming confusion: it started out as a phaser but was later rebranded the "Phasor."1 DOD's separate Phasor line has its own story, covered on the DOD Phasor 201 page, and the FX20B's immediate successor is the DOD FX20C Stereo Phaser.
The depth knob and the sweep
The FX20B's depth knob does double duty. Turning it up raises the phaser sweep as well as the depth, so it acts like a combined depth and manual/frequency control. As Marshall puts it1:
"Turning the depth knob up on the FX20B is like turning both controls up at the same time."
The sweep itself is not symmetrical. Marshall found that the phaser sweep spends more time at the bottom than the top, and that it rises more slowly than it falls, something noticeable at slower speeds.1
Sound and how it sits on a board
Marshall describes "a raw chewiness to the phasing," with a dark tone that cooperates with gain but loses high end with humbuckers. For players running overdrive or distortion, that darkness is a feature; for humbucker players after sparkle, it is a limitation to weigh.1
Two practical quirks to know before putting an FX20B on a board: the bypass switch is sketchy, and the impedance issue is there even when the pedal is bypassed.1
Power is the other practical hurdle. The pedal uses a 1/8-inch power connector, which Marshall notes is not exactly convenient in a day of multi-tap power supplies. It also has a battery door for battery power.12
Finding one today
The FX20B is a discontinued vintage pedal, but it is not hard to find: Marshall notes you can still find them for $35 on your local craigslist.1
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Questions
Is the DOD FX20B true bypass?
Not reliably. Brian Marshall, writing on Subdecay's retrospective of the pedal, called the bypass switch sketchy, meaning the switching can be unreliable in use. He also noted that the pedal's impedance issue is present even when the pedal is bypassed, so the FX20B does not behave like a clean true-bypass pedal even when switched out.
What is the input impedance of the DOD FX20B?
DOD listed the input impedance as 500K ohms, but Brian Marshall measured it at only 100K ohms. That gap matters for players: the lower actual impedance can affect how the pedal interacts with pickups, and Marshall noted the issue remains even when the pedal is bypassed.
Is the DOD FX20B a stereo pedal?
Yes. The FX20B is a stereo phaser, as its full name suggests. Brian Marshall of Subdecay described it as a six-stage stereo phaser and noted that six stages give it a wetter, more pronounced phasing sound than any four-stage phaser.
What is the difference between the DOD FX20B and the Phasor 201?
The FX20B belongs to DOD's later FX series, while the Phasor name came earlier: Marshall notes the pedal started out as a phaser but was later rebranded the Phasor. The Phasor 201 is a separate, earlier DOD design with its own history, including graphic updates in early 1978 and a 2013 reissue.
Does the DOD FX20B lose high end with humbuckers?
Yes, according to Brian Marshall's retrospective. He describes a dark tone that cooperates with gain but loses high end with humbuckers. Players with humbucker-equipped guitars may find the effect darker than expected, while the pedal's character pairs well with overdrive and distortion.
What power connector does the DOD FX20B use?
The FX20B uses a 1/8-inch power connector. Marshall points out that in a day of multi-tap power supplies, this connector is not exactly convenient, so players running modern pedalboard power may need an adapter or a dedicated supply to power it.
Sources (2)
- FX20B: Phaser of Darkness., Subdecay, 2017-04-04
- fx20b-batterydoor, Subdecay, 2017-04-04
