TG-Music Phasers
MXR’s Phase 90 and Phase 45 pedals are legendary guitar effects. These phasers have defined the swirling, whooshing sound that has been a staple in rock and guitar music for decades. Let's take a look at their history and my versions.
MXR, founded in 1973 in Rochester, New York, quickly became synonymous with durable, high-quality effects pedals. The Phase 90, released in the same year, was MXR’s first product and became an instant hit due to its lush, dynamic phasing sound and simplicity of use. Its single knob, labeled "Speed," controlled the rate of the effect.
The Phase 45 followed soon after as a milder version of the Phase 90. While the Phase 90 used a four-stage phasing circuit, the Phase 45 employed a two-stage design, resulting in a subtler and smoother effect. In fact, I like Phase 45 more.
The Phase 90 has been a favorite of countless guitar legends. Eddie Van Halen famously used it and it was a key component of his sound. David Gilmour of Pink Floyd also utilized phasers for atmospheric effects in his work. The Phase 45, though less prominent, has been cherished by players seeking a more understated, or subtle tone.
Make one for yourself
Simplicity of the Phase 90 and especially Phase 45 circuits has made them very popular with DIY pedal builders. These designs use classic op-amp and "JFET as variable resistor" configurations, making them ideal for hobbyists to replicate, modify or enhance. However, in recent years suitable JFETs are becoming hard to find. SMD parts are readily available, but through hole components are getting very expensive. Phase 90 needs four matched JFETs, and while you can use almost any JFET type (that's where bias trimmer will help), even the most common ones like J201 are getting actually rare.
I'm not going to tell you how to match JFETs, beacause geofex has a fantastic article about it here. But in any case, if you don't want to purchase "handpicked" quad, be ready to get atleast ten JFETs, and with luck you will get at least one or two pairs for Phase 45, and maybe one quad if you are lucky. Purchase 20 pcs and you have a very good chance to get matched quad or even two and several pairs.
My versions are what one would expect to get in DIY phasers. Phase 45 is stock version with no mods, but I used 10k resistor networks, just because I had those in my parts bin at a time. in retrospect, I should redesign the pedal with normal resistors. Phase 90 has "script mod" and output boost, and both mods are controlled with simple DIP-switches.
