Subtlesound Inductorless Wah!! ...What?

[MetalUpYerEye]

Alrighty so I built me a Colorsound Inductorless and it sounds neat and everything but the wah wah seems extremely subtle to me, any ideas on how to increase the intensity of this baby? I did substitute .0027uf caps for the .0022uf ones because thats what I had around... Anyways, any ideas on how to beef it up? Thanks a lot.
Josh

[Cliff Schecht]

Subtle? When I built mine, it was probably the most disturbingly unsubtle wah I'd ever heard. I'd stretch to say it's one of the more intense wah sounds available... Are you sure you didn't mess anything up? Also, changing that cap value might change where the sweep is effected, effectively reducing the usable range of the effect.

[MetalUpYerEye]

I'm not sure, maybe I screwed something up but I can barely hear the wah effect unless i rock it back and forth at a pretty good speed while playing. Would it still wah correctly but sound really subtle if the transistor was misbiased?

[MartyMart]

I built one a few weeks ago and have to say also that, "subtle" is NOT what I'd use
to describe it !!
Best Wah that I've had ..... period !
Check it all over, you must have a little "goof" somewhere

MM.

[MetalUpYerEye]

Must be that damned transistor then. Either that or replacing those .0022uf caps with .0027uf made more of a difference than I imagined...

[R.G.]

What schematic did you use?

[Arn C.]

What schematic did you use?

I second this question

Arn C.

[alecacca]

maybe you can increase resonance changing  33k res...

[MetalUpYerEye]

I used the PCB layout by Paul Marossy.

[R.G.]

And where do we find that so we can look at it and tell you what might help?

[Paul Marossy]

And where do we find that so we can look at it and tell you what might help?

http://www.diyguitarist.com/PDF_Files/ColorsoundWahPCB.pdf

I thought mine was nothing to write home about, too. I'm not sure where to find the schematic, but I did get it from a poster at this forum. I hope I didn't make a mistake on it... 

[puretube]

"search" is your friend...

search here for "marossy";
click the link in the 1st result`s thread;
click "search" there;
type: "colorsound" into the field & hit "go";
click the link to the 1 result;
scroll down;
find what you searched...



too late - hit me!

[R.G.]

Thanks for the link Paul.

I drew the schemo from your layout, and put that into the sim. It's not a subtle wah. There's a good 20db peak at resonance. The Q appears to be reduced quite a bit by the 33K in series with the 0.015uF resistor in the R-C-R side of the twin T. The collector biases to 4.74V with nominal values of components, but that will depend heavily on the 5.7M resistor from collector to base. Base voltage is about 0.645.

maybe you can increase resonance changing  33k res...

Yes, you can. But reducing it makes for very sharp, peaky reaponse. 33K makes a nice noticeable 20 db resonance. No diddling should be needed if the rest of the stuff is right.

I think MartyMart is right - there must be some little goof somewhere - soldering, transistor pinout, wrong part value, etc.

[cab42]

CD did this schematic a while ago. I have made a vero layout, if someone should need one.  However I have never build it, so its not verified.

Schematic here:
http://www.diystompboxes.com/smfforum/index.php?topic=25279.msg165637#msg165637

Regards

Carsten

[Paul Marossy]

CD did this schematic a while ago. I have made a vero layout, if someone should need one.  However I have never build it, so its not verified.

Schematic here:
http://www.diystompboxes.com/smfforum/index.php?topic=25279.msg165637#msg165637

Regards

Carsten

That's the schematic that my PCB was designed to.

[oldrocker]

Try this schem.  I used this to make the sewing machine wah.  It seems to work good.  I think it's the same as Paul M's layout.  Maybe you'll be able to see something.  Oops it seems it's already posted for you.
http://img9.exs.cx/img9/4021/cswah.gif

[Dave_B]

"search" is your friend...

search here for "marossy";
click the link in the 1st result`s thread;
click "search" there;
type: "colorsound" into the field & hit "go";
click the link to the 1 result;
scroll down;
find what you searched...

See, that's way too hard.         

[Paul Marossy]

Huh. I didn't know that you could search within your results. That probably explains why I can typically never find something specific that I am looking for. 

[R.G.]

You know, the bane of all simple twin T wahs is that they are unbalanced. The twin T has specific needs for the relationship of the components if the Q is to be constant. Specifically, the two R's in the arms have to be twice the value of the R in the Cap side, and remain that way for all sweeps. The two caps in the cap arm have to be half the capacitance in the cap leg. Most TT designs modify the resistor to ground in the capacitor side and live with the variation in Q, perhaps by unbalancing the C's in the arms.

That doesn't have to be that way. All we have to do is get three resistors to track in value as they are changed.

We select groups of four JFETs for resistance tracking all the time for phase 90 clones. I just simmed up a twin T with four JFETs replacing the R's in a twin T, using two JFETs  in parallel for the resistor-to-ground leg. It gives a constant Q versus sweep.


It looks like four matched JFETs, four identical caps, some 1M biasing resistors and a control voltage give you a voltage controlled Twin T with constant Q and wide sweep. I'll have to work on that some more.

[Paul Marossy]

It looks like four matched JFETs, four identical caps, some 1M biasing resistors and a control voltage give you a voltage controlled Twin T with constant Q and wide sweep. I'll have to work on that some more.

Very interesting idea!