need advice of some wise men...

[fonik]

as some of you might already have recognized, i have some trouble with the cheap panier design. actually it was meant that way: just a cheap extension for the resonators.
however, people are not that happy with how it works, they expected more. obviously it has been my weak communication - my fault.

do you have some wise advice how to mitigate?

i could think of offering refund, and documenting a kludge for the board (will have to put it on the breadboard again, which will take some time). BTW Teknik (mod helper here?) didn't want any refund.

i am really interested in doing all necessary to solve the problem, so any comments, suggestions or advices are appreciated.

[Uncle Krunkus]

What's the "cheap panier design"?

[blue hell]

teknik is a pita imho

diy helpers are :

[blue hell]

[fonik]

it is the PS3100 3rd run thread:
http://electro-music.com/forum/topic-29164-200.html

maybe it would be cool to split the panner vca issue off? i dunno.
however, i did not do a good job with the x-panner. but i liked to get it right for all involved.

[blue hell]

Hmm .. I don't think your communication has been that weak actually .. skimming through the thread I read several warning signs ... what is the big trouble now? The CV bleed through? The BOM issues seem minor to me ...

[blue hell]

Hmm maybe never name a module "doubletrouble"

[fonik]

[blue hell]

Ok, so the first question is ... does this need a fix or not ... it seems clear to me from the thread that you intended this to be a nice add-on for the resonator and not as a standalone module. Would it, in that light, not perform as advertised? I don't find an indication for that in the thread.

[yusynth]

Hi Matthias

I have just found this thread and then I had a look to your X-panner schematic and the problem with your circuit is that with such a simple design of the VCAs you must use very well matched components with tight tolerance (transistors and resistors).
In such a circuit the CV bleed-through is mainly due to the mis-balance of the differential transistor stage. The idea behind a cascode circuit is that the collector currents created by the current sink is perfectly balanced and therefore cancel each other in the differential circuit built around the AOP. If there is a slight inbalance in the values of Q1 and Q2, R1,R2,R4,R5,R11,R3. Usually it is a good practice to have a small trimmer (say 1K) inserted between R1 and R2 and the +15V rail : the trimmer connected by its extreme terminals to R1 and R2 and its wiper pin connected to +15V. This way one can adjust the trimmer to minimize the unbalance and reduce the CV bleed-through.

Another point could be improved by using DC blocking caps (say 10µF) in the signal inputs of your VC-panner.

I hope these comments may help you

Yves

[fonik]

thank you jan, thank you yves.

thank you jan for giving me confidence. you are right. it was meant as an extension board and i did communicate that it is not a top notch stand alone VCA design.
thank you yves for your technical comments. i still remember your kind assistance when building my first modules (EFM).

i think i will do the following: again making clear what the x-panner is and what it meant to be. ammend the documentation accordingly.
then i will workout a kludge for the PCB and document this as well (will take a little bit longer, since i will have to build it up).

what do you guys think?

[blue hell]

That sounds like a good plan to me Matthias.

Maybe you could announce that you are searching for a patch up for people having offset / bleed through problems, and that such will take a while.

Meanwhile I think that the trimmer fix proposed by Yves could be mentioned already for people who want to experiment on their own - seems to me that it would do the trick. Less confident people would have to wait a bit then.

[fonik]

obviously i am on a good way now. thank you a bunch for your support, jan & yves.

[blue hell]

Even teknik behaves well, you must be doing something right