Where to put a mix control on a Boss DC2 dimension C?

[Morocotopo]

Hi. Me again with questions, questions... maybe someone can help me.

I´m working on a Boss Dimension C clone, I modified the schem to replace some unavailable parts like the flip flop IC and the preset buttons, already made the PCB, it´s a double decker! Meaning I made it in two separate stacked PCB´s to be able to fit it into a reasonable size box. Successfully, I might add, it´s working very nicely at the moment. Later, once it´s finished and boxed, I´ll make a thread.

But, but, but...

I want, besides the rate and depth controls, to have a mix pot, so that I can get a really, really subtle chorus, just a hint of shimmer, the kind you only notice when you turn it off. As it is the effect, while subtler than most other choruses is still too much for me. I love the thing, I just want less of it!

Then the thing is: Where to add a mix control? Or at least a more/less mix toggle switch, maybe even with three positions?
Looking at the schem (Thumb view because the schem file is BIG - around 4 meg):



I see, well, a complex schem that I don´t fully understand!
First I searched for the mix resistors, I believe those are R82, R85 for the wet signal. but since this is a stereo out FX, there´s also R86 that I believe is also a mix resistor for the second output when in mono mode. Triple pot? Yeah, try to get one of those here in Argentina... also, R86 is a different value than R82 and R85. So that idea won´t work.

Where else to add a mix pot?
Well, here´s the possibilities I -believe- could work:

- Between Q5´s emitter and R62/R29?
- Between C9 and IC2´s pin 6?
- Between IC11 pin 6/7 and C13 and between C59 and R82?
- ...?

Well, those are the options I can think of looking at the schem. Does anybody sees another option to get a mix control of some sort?
Before you say "just try them!", the thing is not so easy to dissasemble, due to the double tier construction mentioned before, and lots of wires linking the two PCB´s, so I want to have a clear idea of where to work before I take it apart.

Any help more than welcome!

Morocotopo

[Fender3D]

Would a "Chorus Level" be enough?
I would place a stereo level pot at IC11 outs (add capacitors though...)

[Morocotopo]

Federico, nice idea. I might have to tear it apart and just experiment.

[Morocotopo]

Guys, the more I look at the schem the less ideas... anyone?

[Mark Hammer]

I'm thinking R85/R86 are the optimal points to intervene.  Past that point, and you're dealing with multiple outputs, that whole stereo outputs things and such.  At R85/R86, you're dealing with the last level-limiting resistance for the companded output of each delay path.

There may be other ways, but I'm thinking that a dual-ganged 10k pot, inseries with each of those resistors is probably all you need.

[Morocotopo]

Thanks Mark. The thing is that there´s also R82 there, that I think s also a mixing resistor. Actually, If I´m not mistaken, the mixing resistors are R82/85, and R86 is a third one for when the second out jack opens the FET Q3, to combine or split the signal for stero/mono, not really sure. So in one of the modes (mono or stereo, not sure), if that one doesn´t have a series pot, the wet/dry balance would be off when using the pot. At least that´s what I think...

[Mark Hammer]

Nope, you are right, and I'm wrong.  Got tripped up by the switching back and forth between windows. 

Yes, R82 IS the analog of R85.

R86 is a mixing resistor for the same source as R85, when a person uses both outputs instead of just one.

In effect, the chorus intensity option I described before works when running the pedal in stereo.  If one is running it in mono, then the added resistance needs to be combined with R86.

All of which makes me wonder if it wouldn't be easier to use a 3PDT center-off toggle to select one of three mix levels for the delay side.  That would let you compensate for the different resistance value of R86 vs R85.

[Morocotopo]

Well Mark, the toggle idea is starting to look like the most straightforward one. i was kind of set on adding a pot to get all the shadings, but...
As a matter of fact I just bought last week a few 3PDT on-off-on toggles. Hmmm.

[Fender3D]

Connect:
potA lug3 to C13+ (you should lift it from PCB, measure voltage at its pins it might be reversed, higher voltage to +)
potA lug2 to 10uF- (see above) then 10uF+ (see above) to node Q3-C60-R91
potA lug1 to GND

potB lug3 to 10uF- then 10uF+ to IC11 pins11/10
potB lug2 to 10uF- then 10uF+ to C59
potB lug1 to GND

Pot value 10K-100K log should work (lugs 3 CW)

[Morocotopo]

Cool! let´s see if I got it right. Like this?



So you would get no DC on the pots, right? Smart guy, you... I´ll try it as soon as possible.

Gracias Federico!

EDIT: oops, in this configuration, C13 should be reversed ´cause the pot side would be at 0V. I think. More so since I plan to try tantalum caps.

[Fender3D]

Yesssssssss

That's what I figured out

Let us know if it works properly.
As a side note, perhaps shorting totally the wet signal to GND might be too much...
Consider adding a series resistor ala BigMuff sustain control 

[Morocotopo]

Perrfect. I´ll try it as soon as the damned work gets out of the way.

Thanks again.

[tiarlei crist]

Hi.

I suggest 100kB for VR1, 200k (B or C) for VR2 and 33k for R37.
Will be perfect.

Bye.

[Morocotopo]

Tiarlei, thanks. But I never put a mix control in it (It´s already boxed and finished), because at minimum depth and rate, the thing was so sublte that a mix control is not really needed. It was a good exercise to think/plan this mod anyway. Thanks all for the help.