Re: MXR Script vs Block - check out Mick Mars cover guitar rag
The later block logo Phase 90's added the feedback circuit, which gives that extra "swish" to the sound, which is very noticeable when you use a distorted amp or pedals. The "Script" circuit has no feedback, and that's why it sounds better IMO with distortion. The early block logos had pretty much the Script circuit (with subtle changes), but later block logos added the feedback, which is what Dunlop decided to clone when they first started making the MXR pedals again. So there is a pretty noticeable difference in the sound of a "late" block logo (or early Dunlop MXR) Phase 90 from the Script and early block logo pedals. So, I think that article is misleading. There were other small changes to the circuits along the line, but the feedback circuit addition is the biggest change they made. The early EVH Phase 90 sound is a script circuit. The circuit with the feedback sounds all right with clean sounds and keyboard guys like them, but with distortion the extreme swish can become annoying IMO.
Al