Added Phaser Stages, insertion point options [P-90 this time

[petemoore]

  Viewing this more as a quiery as stated in stone, how would you bias and where would you insert additional phase stages in the P-90?
 http://www.geofex.com/FX_images/p180.gif
  Oriented toward additional swept stages, the insertion point for stage pairs being after the first two phasing stages, where the circle crosses the signal path on it's left side.
 I'm working on a P-90 with a PCB with unknown trace-age, the 3x150k's at the end of the phase stages is easy to locate, as is the 10k>.01uf>470k at the input stage.
  It looks like it'd be easy...lift the opamp #3 opamp pin from the socket...there's the insertion point if I can find it..
  But then there's the V-bias, on the schem it shows a bias pot between 3v and Gnd., it's output goes through the Jfets to the +pins, I'm confused by this.
  It's either that or near the input, after the first opamp.
 Inside the feedback loop I think !
 What difference would result in putting the 2 new stages in the middle of the existing phasing stages instead of at the front or after the last phase stage ?
 My guess is "maybe a little different"...never tried it.
 If four additional stages were to be added, of course it'd be neater and cleaner to daughter board 2 dual opamps and use 1 insertion point [cut 'n splice].
 Another option could be pick 2 insertion points and still use two duals for 4 added stages?> Seems logical that it'd work, but I haven't heard of it being tried.
 

[Mark Hammer]

Stick them in the middle.  That way the regeneration path will be through the "correct" number of stages (i.e., an odd number).  I stuck the added two fixed stages between X and Y on the Tonepad Ropez board, which is an insertion point between stages 2 and 3.  Works great.  With the Small Stone, it's a little different since the regen path goes right back to the beginning (even #stages).

[petemoore]

  As phasers go, I find single oa's easier to count, this has LM741's.
  Should be too hard to follow through a couple opamps and 10k's to find #3's output pin, pull, splice.
  I guess I'll just tie the 10k's to the Jfet gates, I don't understand why they wouldn't be happier before the voltage divider bias pot though, connected to the Vbias3v.
  http://www.geofex.com/FX_images/p180.gif

[petemoore]

  Thanks again, the timely critical information specific to the P-90 Mark !
  This went right in and fired right up after some debugs, very nice too !
  I don't know...I left that 'extra' 10k I put in there...where I pulled the opamp output pin, 3rd opamp ''splice-in-point''...I put a 10k feedback resistor [to -input] there, schemati-gazing, it still seems like it should have one there.
  And did find .01uf and used a .015uf to use for a time to try it out, not sure what difference that'll do, seems to work and marks where the .01uf will go when it's ready to get in there.
  The ''syrup'' seems sweeter, a more complex flavor and thicker this way.

[Slade]

Look here! 
http://www.diystompboxes.com/smfforum/index.php?topic=77326.0

[petemoore]

  Slade Phase is a Wowzer !
  er...sounds like it's saying WoWZeR when sweeping w/depth and resonance turned up.