OK, I really mean it this time. It's done. Finie. Fertig, Finito.
The switch on the left is for shifting the duty factor. Green knob: SPEED; White knob: DEPTH; Yellow knob: COLOR; Switch: RESONANCE. The army of JFETs just below the knobs are matched sets: 2N5484, 2N5952, 2SK30A-Y, BF244A. They all work. I have BF244B installed in the circuit. They have a higher Vp (around 2.1V) which yields more headroom.
Changes from the last schematic:
Added R50 to isolate Q5 from the next device in the chain.
Reduced R18 to give Q5 a little more headroom.
Added R51. This is routine in my circuits now.
Added R52 to bring the LFO duty factor close to 50%. The sweep sounds more "balanced" to me.
Reduced R24 for a little more sweep when DEPTH is dimed.
Put the Bias Trim (TR1, R47 & R48) back in.
Added R46 which controls the range of the COLOR knob.
Added C11 to block DC from the LFO signal, which makes DEPTH & COLOR less interactive.
Replaced D1 & R101 with a 78L05 regulator. More stable than a zener. C10 should be 1uF tantalum or film. Do not use a larger cap, it can make the 78L05 oscillate.
Replaced the RESONANCE pot with an ON-OFF-ON switch.
RESONANCE has three settings: Script, Block Logo and 1/2-way in between. I had a knob for RESONANCE, but there were only three useful settings so I replaced the knob with a switch. I have all 47nF caps installed in the phase shifters. With the right DEPTH and COLOR settings, it does a pretty convincing UniVibe tone. As such, I don't see the need for stagger-tuning. Those of you who are breadboarding this can try it both ways and form your own opinion.
NOTE: schematic corrected
If what you want is a stock Phase 90, then by all means build the XC Phase.
If you want a 1-knob phase shifter that sounds like a Phase 90 but has more headroom, then build this and jumper all three pins of the DEPTH control, jumper C11, change R24 to 3.9M, change R25 to 1M, omit R46 and the COLOR control and change R52 to 2.2M.
If you want a sort-of UniVibe, then use the stagger-tuned capacitor values. The RESONANCE switch, R27 & R28 are optional.
If you want a hopped-up Phase 90, then build it as shown, but with C2-C5 = 47nF.