silly feline/funny cat

[mantella]

Hi all,
first-timer here, so be gentle 

I've built several (working) pedals now from schematics, but have no real background in electronics so my de-bugging skills are pretty poor.
I made the silly feline based off of the GGG project. I got it working to the point of having a sound come through, but it's not really doing what it's supposed to do.
The sound I get is like a muffled (closed filtered) sound. It's like the auto-wah isn't being triggered by my guitar signal.
I added a bobtavia in front of it to boost the signal, and that seems to help. But, I want the sound to work with my clean channel, and only the guitar if possible. I've tried swapping out Rfba from 470 to 1M (I tried much higher resistance as well, but with no luck). I've used the NTE458 for Q1 and NE5532 for the op-amps. Tried some TL072's as well, but it didn't change anything.

Anyways, if anyone has any ideas about what else I could try that would be greatly appreciated. I just saw on an old post that R10 should be 15K instead of 47K, so I'll try that today as well.

Thanks!
Great forum, btw...

[biggy boy]

Hi Mantella
Welcome to the forum.
Hope you find what you need here, yes it is a great forum.
Did you try the debugging thread?

What to do when it doesn't work

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

Glen

[Mark Hammer]

Swapping chips will do nothing in this instance.  They either work, or they don't.

There are two sorts of envelope-controlled effects going on here.  One is the feedback that is applied from the output of Module A to the 2SK30A that determines the gain of that op-amp and the "soft distortion" effect.  The second is the envelope follower that determines the sweep of the filter itself.  Rfba sets the gain of the first stage for the soft distortion.  R10 helps set the gain of Module B1.  If you are using the PCB to build it, I believe the PCB is correct (well, at least mine works).  The drawing is slightly incorrect, though.  The Mode switch should really connect R10 to R26, the R26/R25 junction, or ground, such that the resistance between C8 and ground is either R10, R10+R25, or R10+R25+R26.  That will provide three different amounts of gain for Module B that will complement the 3 different sweep types provided by the other half of the Mode switch.

Since the gain of Module B1 is a function of R10, R25, and R26, changes to R10's value CAN have an impact on the sweep, but once you stick R26+R25 in there, not that much impact.  Personally, I think a far better solution is to ignore that half of the mode switch, and replace R10 with a 15k resistor in series with a 100k linear pot, and connect THAT to ground.  This will mimic the entire range of sensitivities captured by the stock Mode switch, but allow for better matching between your playing and the needs of each sweep mode.

You will note that the right side of the Mode switch really only selects between TWO sweep types, even though there are 3 Modes.  One sweep type is taken directly from R11 without any ripple filtering in order to drive the filter crazy with ripple.  The other sweep type adds another 12k of series resistance and a 47uf cap to ground to "soften" the sweep with a bit of attack time, and remove a bit more of the ripple via C19.  What all of this means is that you can replace that bulky and hard-to-solder 3-position rotary switch with a standard-issue 100k pot and a SPDT toggle that connects R24 to R23 or R11.

Again, note that these mods still permit you to nail all the tones of the stock unit.

[mantella]

wow, thanks for the great response! I'll give these a try and let you know how it worked.

[dr.benway]

Hi Mantella,

I'm pretty much in the same situation with the funny cat. I was wondering if you tried Mark Hammer's suggestion of replacing the mode button aand if you got the thing to work better. If so would you happen to have some pics of the connections ?

Thanks.

[mantella]

Hey Doc,
I didn't replace the rotary switch. What I did do was to replace R10 with a 15k resistor in series with a 100k linear pot, and connected that to ground as Mark suggested. I didn't change anything for me.
I've un-soldered and re-soldered that stupid switch so many times that I don't want to mess with it anymore unless I think that's really the issue. And I don't really think that's the issue. I can get the switch to do what it's supposed to, as far as I can tell. But I just can't get the envelope to open and close properly.
It's super frustrating because whenever I plug or unplug a connection from it, it will make the bwow sound. It just doesn't want to do it when I'm playing 

I think it's a resistor or capacitor that's wrong somewhere but I haven't tracked it down yet. I kind of took a break from it for a few days. I'll get back to it this weekend though and let you know if I have any luck.

[The French connection]

It's super frustrating because whenever I plug or unplug a connection from it, it will make the bwow sound. It just doesn't want to do it when I'm playing 

Have you check the wiring around those plug? Are you talking about the input and/or output?

Dan

[mantella]

Mark Hammer - I'm just getting around to this pedal again after finishing up some others...

I don't suppose you'd be willing to draw up that wiring connection you're talking about?
It would really help some of us newbies who are still at the mercy of the wiring diagrams shown on these projects. When there's one floating around that's incorrect, I'm sure it keeps a lot of folks frustrated and scratching their heads for a long time.

[Mark Hammer]

Here is what I am suggesting.  It offers more variation than the original, and a somewhat wider range of sweep sensitivity.:

Thanks to my good friend RG for the original drawing.

[mantella]

Thanks so much, that's a great mod.
I'm still getting a weird sound though, as if the filter doesn't want to open and close when I hit the strings. It sounds like a crybaby pedal that's on, but left all the way in the up position.
I have Rfbb and Rfbc wired up with alligator clips to 500k pots, and as I touch the leads to the lugs, I get the "wah" sound. But as soon as the connection is made, it won't do it anymore. Does that make sense? Everything seems to be working with the circuit now, except for that.

Could it be the transistor I'm using? I used NTE458 for Q1 because I couldn't find the 2SK30A anywhere. I also tried some other JFETs with interesting, but not really successful, results. I've also tried a bunch of different values for Rfba, but still no good.

Thanks again Mark for taking the time to mod that scheme!

[R.G.]

Could it be the transistor I'm using? I used NTE458 for Q1 because I couldn't find the 2SK30A anywhere. I also tried some other JFETs with interesting, but not really successful, results. I've also tried a bunch of different values for Rfba, but still no good.

It could well be. Try a 2N5485 or 2N5292.

Your description of the wah as stuck at the high end indicates that the opamp that drives the wah is misbiased and never goes into the linear region.