Improving a SS, adding dual OA stages, what is IC6 of Boss RPH-10 ?

[petemoore]

  First question: RPH-10's IC6 is a Dual Opamp ?[see Mark Hammers recent 'Improves almost any Phaser' thread.
  Whoops, search "RPH-10 schematic"- finds:
  http://hammer.ampage.org/
  With this in it: Boss's proprietary IR3109 quad OTA chips as well as companding to make the IR3109s behave
 Well I built a Dual OA board, using all 10k resistors, following the circuit around IC6...any suggestions for what I could plug in the 8 pin IC socket ?
  I believe I can find around here CA3080's, not so sure about the CA3904's...hmmm searching again.
  The Small Stone has a 470ohm filtering resistor, this drops about a volt.
  The SS has a 10k><15K voltage divider though, and this is where I tapped the Vbias to, it produces voltages around 2.2v on the opamp pins [pin 8 of TL082 reads about 7.95v when connected on the inside of the 470ohm, 8.95v when connected to the battery, pin 4 is Gnd'd.
  The Small Stone has a 470ohm filtering resistor, this drops about a volt.
 The input node has a .01uf [to +input] and R to -input.
 -input also gets the feedback R
 +input gets the Vbias R
 The first stage feeds the identical second stage.
 The Small Stone has a 470ohm filtering resistor, this drops about a volt.
 That leaves the input and the output of the daughter board, at the output, I get swirly noise [ie the rest of the phaser is working, and even at the 1rst OA inputs of the daughter board I get swirling, none though at the cut trace or the 10k/.01uf, the daughter circuit input.
 There are three resistors sorta centered across the bottom of the Tonepad board [when Q6 is at bottom right corner], a slightly wider gap between the middle and left resistors [R33 and R41], this gap is where I drilled trace and tested non-continuity, spliced in the daughter board signal wires, yupp, input from the right [Q6 emitter] output to the left.
Using a touched screwdriver shank effectively as a noise injector, no clicks or noise from the input side of the daughter board [at the 10k/.01uf], nice swirly noise at the input pins of the OA though.
 Oh yea, everthing looks right, but I forgot the y in everything now didn't I ?
 Seems it could be the ould it be the 10k/15k bias point?

[Mark Hammer]

Yes, pete, it IS a dual op-amp.  That's the thing about the RPH-10 and the PH-2.  They both use 8 stages of OTA-based phase-shift, using the IR3109 chip, and supplement that with additional fixed stages of phase-shift using op-amps.  The PH-2 schematic says those op-amps are IR9022, which is a proprietary number for Boss, but let's assume it's probably just a TL022 by another name.

If you want to stick two additional fixed stages into a Small Stone, then it seems to me that the simplest place to stick them is after the last 3095/3080-based stage, but before the point where you see the 27k mixing resistor for combining wet with dry,and the point where that 27k resistor meets the 3k3 resistor heading off to the regeneration loop.

Make sense?

[petemoore]

  Wow ! sounds thicker/deeper than before, a very sensible mod now, thanks for mentioning and helping me work up this mod Mark !
  I had a 10k cold soldered to a 10k...go figure !
 Still wondering what a couple more stages would sound like, say cut/spliced between Q10e/3k3...last shot was sensible, tighter width than length inside the wah case, I already have a booster where the rack 'n pinion used to move.
 

[Mark Hammer]

Glad it worked out so well for you.  Given the postage-stamp size of the add-on-board-plus-5-wires (in, out, V+, Vb, Gnd), it seems like an easy add-on for anyone who wants to spice up their meat-and-potatoes 4-stager.  So, not only Small Stone or Ross, but P-90, Rocktek, or anything else with 4 FETs on the board.  Will it fit in one of those 1590A pedals?  I have my doubts.

[petemoore]

Will it fit in one of those 1590A pedals?  I have my doubts.
  I have a Phase 90 powered by a Spyder's leg, that makes an empty battery compartment !
  Have you tried 2-swept>2-fixed>2-swept>2-fixed stages in what used to be a 4 stage phaser yet ?   

[Mark Hammer]

No.  I quit at 2 added stages.  I am, however, looking forward to trying out an addition 4 stages as part of "theta processing" for a largish flanger project. (See Jurgen Haible's Storm Tide Flanger)

[petemoore]

  I had a Ross Flanger for a long time, a long time ago !
  Lookin' at the P-90 now, starting another thread about additional phaser stage insertion points..