Colorsound Flanger output

[armdnrdy]

I've been mulling over the Colorsound Flanger schematic that's running around on the net.

I've gathered some component side board shots, but cannot seem to find any trace images.

The images that I've collected show two different versions. The schematic reflects this as there are component value changes, resistors deleted, and trimmers added.

One change is at the output. The original version used two resistors R32 & R38 to mix the dry and delayed signals. The "updated" version replaced the resistors with a 47K trimmer to dial the circuit in for optimum notches.

Now the problem...maybe it's my inexperience but...the output on the drawing doesn't make much sense to me!

I've re-drawn what I think I see...and threw in what I think would work as another option.
Any ideas which would work?

Here's the original drawing:


Here are the three options. The last one, option III, I threw in as what I think would work:

[armdnrdy]

Update:

I just tried connecting a meter to a pot in the first two configurations.

Option I does absolutely nothing when the wiper is connected to lugs 1 & 3. (not surprising)

Option II with the two outer lugs connected exhibits a very interesting, unexpected behavior.
When in the CCW position, there is low resistance.
When turned CW, resistance increases until about halfway when the resistance decreases all the way to low resistance when fully CW.
Max resistance at half way point is equal to about 1/4 of overall resistance of pot.

So...I believe that this configuration would be used to mix together two signals.

[armdnrdy]

Update II 

I was studying the original drawing when I looked at how the 1K BBD balance trimmer was drawn in after the fact.
The resistors are crossed out but it appears that lugs 1 & 3 are connected to the wiper.
(just like at the output)

Well...I know how a BBD balance trimmer is implemented so...I think that the output balance would be correct with option III of my drawing.

Any corroborating testimony? 

[Scruffie]

The audio path looks much the same as the electric mistress (albeit with a transistor input buffer instead of opamp and different values) seems to me that output trim is for setting the wet/dry mix...

The 22k being the wet, 27k being the dry obviously.

It seems to me option 1 is how it's drawn, the balance trim has the legs shorted like that too.

[Mark Hammer]

Option III strikes me as the only one in which tweaking the trimmer would actually do anything.

[armdnrdy]

Option III strikes me as the only one in which tweaking the trimmer would actually do anything.

Thanks for the replies.

I agree Mark. My initial instinct led me to draw option III even though it was clearly not depicted that way.

I guess whoever drew in the revisions didn't have an erasure handy that day! 

@Scruffie
It sure is close to the standard EM. I was looking for something similar. I knew I had seen a flanger circuit that was kind of "bare bones" after the BBD but...I couldn't recall which one it was! Thanks for that.

The Deluxe EM had the added BBD balance trim that the Colorsound added around 1981.
It looks like the CS folks were taking a look at other effects for ideas.

[Fender3D]

Hey Larry,

you did a very thorough job, as always...

Just a question:
I never heard it, but, looking the schematic, I think it should have a virtual GND buffer (inverting op-amp) at the end of your option III (the only one working... logically) to avoid any interference.
Notice that BBD's output goes to 1st opamp's non inverting input and without a proper decoupling might enter... BBD's input via the "dry" path...
I'm too tired right now (2 a.m. here) to check out what may happen with that differential...
but following my nose... hmm

then there's that over-complicated LFO-VCO stuff, hell, it's more complicated than the signal path!!! 

Question 2 (I lied above)
you're looking for trace side, then...
where did you find those SADs, you lucky ***...?

[Govmnt_Lacky]

I still have some stock of R5106 and R5107 BBDs if you are interested for testing 

Might need a few value changes but.... it is a pretty close match to the SAD512 

Let me know if you need some.... I owe you anyways! 

[armdnrdy]

Hey Federico,

I see the areas you are referring to, and the possible issues but, if you look at the standard Electric Mistress drawings...the signal/BBD path is almost identical.

http://www.metzgerralf.de/elekt/stomp/mistress/images/1976-electric-mistress-v2-schematic.gif

So...I guess the design works.

I agree this circuit is kind of a train wreck compared to some flangers such as the Mutron or ADA!
With that being said...that is one of the things that made me take notice.
This design looks older than it is. (The drawings are dated 1977)

The oscillator configured out of a CA3046, "bare bones" filtering, no output buffer after the BBD, discrete voltage regulator....This thing looks like a real relic!

I've gathered all of the component side board shots I can find which allowed me to at least verify most of the changes drawn in on the schematic. I'm currently working on a redraw..and than I'll use the component layout in the images as a reference to route a board.

It would be much easier to trash all of the over-complicated circuitry and "modernize" the design but...that just wouldn't be as fun! 

[armdnrdy]

I still have some stock of R5106 and R5107 BBDs if you are interested for testing 

Might need a few value changes but.... it is a pretty close match to the SAD512 

Let me know if you need some.... I owe you anyways! 

You don't have to twist my arm much to accept an offer for BBDs! 

We'll have to talk.