Enclosure not stated · 1 knob
MXR Script Phase 90Verified
Based on the MXR Phase 90· 14 other boards clone it
From the post
The Script version of the Phase 90 is probably the holy grail of phase shifters and was the first effect released by MXR in 1973. It's probably most famous for helping create Eddie Van Halen's brown sound on the first 2 Van Halen albums. It was designed before dual op amps were really affordable, so it used 6 op amps, in addition to 4 JFETs and a PNP silicon transistor. I've wanted to do a layout for the Phase 90 for a while, but all those op amps intimidated me, so I held off till a request for it came in. I used the original MXR board as a starting point. I ended up with 2 jumpers, but original units had a 150k resistor spanning over half the board (going from the base of Q5 to pin 6 of IC5).
One of the weird things about this layout is how the JFETs are oriented. The drain and source pads are further apart than the source and gate pads because the ground fill has to go between those gaps, and this quirk is evident on the original board from MXR. I would imagine 2N5457s would work if you can't get ahold of the original 2N5952s, and a 2N3906 can be swapped for the 2N4125 if necessary. Also, if you're not a fan 741 chips, a TL061 or 071 should work fine.
Schematic
This is a board layout, a drawing of where each part goes, and the post may link the schematic it was drawn from. Open the layout at Effects Layouts (blog). No KiCad fragment has been drawn for this circuit yet.
Parts list 21 rows
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Check before you build · 1 value the reader of this layout was not sure of
- 15uF electrolytic bottom right next to the 250k trimmer: printed clearly, unusual value
| Ref | Value | Normalized | Type | Notes |
|---|---|---|---|---|
| Resistors 9 | ||||
| ×11 | 10K | 10k | read from the layout by eye | |
| ×6 | 150K | 150k | read from the layout by eye | |
| ×4 | 22K | 22k | read from the layout by eye | |
| ×2 | 470K | 470k | read from the layout by eye | |
| ×1 | 56K | 56k | read from the layout by eye | |
| ×1 | 2.2K | 2.2k | read from the layout by eye | |
| ×1 | 4.7K | 4.7k | read from the layout by eye | |
| ×1 | 1M | 1M | read from the layout by eye | |
| ×1 | 3.9M | 3.9M | read from the layout by eye | |
| Capacitors 5 | ||||
| ×6 | 47nF | 47n | read from the layout by eye | |
| ×2 | 10nF | 10n | read from the layout by eye | |
| ×1 | 10uF | 10u | electrolytic; read from the layout by eye | |
| ×1 | 15uF | 15u | electrolytic; read from the layout by eye | |
| ×1 | 100uF | 100u | electrolytic; read from the layout by eye | |
| Diodes 2 | ||||
| ×1 | 1N4001 | 1N4001 | read from the layout by eye | |
| ×1 | 5.1V | 5V1 | zener; read from the layout by eye | |
| Transistors 2 | ||||
| ×4 | 2N5952 | 2N5952 | Q1-4, JFET; read from the layout by eye | |
| Q5 | 2N4125 | 2N4125 | read from the layout by eye | |
| ICs 1 | ||||
| ×6 | 741 | 741 | read from the layout by eye | |
| Potentiometers 1 | ||||
| Speed | C500K | C500k | Potentiometer | read from the layout by eye |
| Trimmers 1 | ||||
| ×1 | 250K | 250k | read from the layout by eye | |
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