Problems with the Phase 90 schematic

[imzuker]

So i want my next project to be MXR phase 90.
so i got these schematics http://www.tonepad.com/getFile.asp?id=42 and i don't really understand them so i have a few questions.
1.what does the IC 1a/2a/3a/2b mean? i get its is supposed to be an IC but in the parts list there is only 3 chips and in the schematics there are 6.
2. what does the numbers around the ICs mean? some have 1,2,3,4 and some 1,2,3,8 or something.
3. why some of the resistors are red?
4. what modifications can i make in this schematic?

[fpaul]

TL072 are dual opamps, so there are two in each chip.

The numbers are the pin numbers.  I suggest you look at a datasheet for TL072.

For mods look at the build reports at tonepad or search the forum.

[Seljer]

The red parts are the ones you can adjust for various mods, as already noted on the tonepad page

Possible mods: "The resistor you pull to get rid of the feedback (and change the sweep) is the red 22k at the top of the schematic. The resistor to change the level is the 150k which connects between the collector and base of the PNP transistor: 120k to reduce gain, 180k to increase it." Rob Strand

The 1Megaohm resitor can be change into a potentiometer for a 'depth' control
The 4k7 resistor sets the maximum speed of the rate control, if you want to go faster try 3k3 or 2k2

I've built this and can vouch that it sounds perfectly fine without any mods (I messed around with the that 22k feedback resistor but in the end I left it out for a 'script' phase 90)