Q About the ColorSound Wah

analog kid · July 01, 2005, 12:22:20 AM

What would (most likely candidate at least) cause THIS circuit to act as a volume pedal rather than wah with the sweep??
I've built it twice now with two different layouts and both times all I get is a slight Volume effect!
I know with an inductor based wah that the electrolytic cap OR the inductor itself being bad can cause this but with a crkt like this one I just don't know how many things may cause this??
deviations from the schematic are:
a .0082 uf polystyrene cap in place of the .0062 uf called for.
and 150k/33k resistors in series in place of both 180k resistors.
Any ideas??

jmasciswannabe · July 01, 2005, 12:35:24 AM

Paul - Thanks a lot for all the recent wah posts and especally for following up on Commonsound! I am going to perf it tomorrow thanks to your layout diagram. I have been interested in this one for a while because I have heard it has a huge sweep....I am also getting a red and yellow fasel for the moddable wah at over ggg.....so its going to be a wahnnderful weekend.

:oops: Ya i know...that was bad.

chrishopkins · July 01, 2005, 05:30:18 AM

I've got an old Frontline Wah that could do with a good pcb inside it so will give the Coloursound a go. Think I'll socket the output resistor and the jumper to give me the option of allowing for a Q control later

What's a good HFE for the trannie and which caps would I need to change to alter the frequency response? Im thinking of adding a rotary switch to do that ala the vox/crybaby mods.

Paul Marossy · July 01, 2005, 05:47:33 PM

Quote from: jmasciswannabePaul - Thanks a lot for all the recent wah posts and especally for following up on Commonsound! I am going to perf it tomorrow thanks to your layout diagram. I have been interested in this one for a while because I have heard it has a huge sweep....I am also getting a red and yellow fasel for the moddable wah at over ggg.....so its going to be a wahnnderful weekend. :oops: Ya i know...that was bad.

You're welcome. Hopefully you have better luck getting yours to work than analog kid. I know my layout works because I built my own from it. And, yes, it does have a large sweep.

Quote from: chrishopkinsI've got an old Frontline Wah that could do with a good pcb inside it so will give the Coloursound a go. Think I'll socket the output resistor and the jumper to give me the option of allowing for a Q control later

What's a good HFE for the trannie and which caps would I need to change to alter the frequency response? Im thinking of adding a rotary switch to do that ala the vox/crybaby mods.

I used a 2N5089 in mine. Hfe is somewhere around 600-700. On how to shift the frequency response, read the "Technology of Wah Pedals" at www.geofex.com - towards the end of the page.

chrishopkins · July 01, 2005, 06:13:02 PM

Quote
I used a 2N5089 in mine. Hfe is somewhere around 600-700. On how to shift the frequency response, read the "Technology of Wah Pedals" at www.geofex.com - towards the end of the page.

Is this the circuit?

If I want to change the frequency response do I change the 0.1uF in the first T or the two 0.005uFs in the 2nd T? Sorry if I appear to be a complete noob about this (A Level in Electronics and do you think he can remember any of it???)

analog kid · July 01, 2005, 07:59:29 PM

This brings a couple of questions to mind looking at that TwinT schem shown in RG's article.]
I was really concerned about which component values (especially the ones in the "T" of the crkt) had to be RIGHT ON for the crkt to work and which ones could be played around with a good bit and still have the effect.
The components in this one look almost nothing like the ones in the colorsound! Value wise. For instance I didn't have any 180k resistors for the T so I diddled with some series and parallels to get close. I thought this was keeping it from working. WELL there are 33k resistors in there on this one!!!! and the .0022uf and .0068uf caps in series at the bottom of the schem are replaced with two .005uf's . That makes me think (assuming these two designs are the most part the same)that two .0047uf 's could be used here. And I guess anything between 33k and 180k for the T resistors>?
SO are the values interchangable between the colorsound and RG's Twin T schematic ? or are there other things going on in each that makes the differing values WORK?]
ALSO : Why is there a second transistor in the schem on GEO?? Is it ONLY for adding that Volume control in there?

Paul Marossy · July 01, 2005, 11:19:01 PM

chrishopkins-

Yep, that's one example of a Twin-T circuit. I believe that you would have to change the resistor and cap values in both Ts to shift the frequency response. I don't really know for sure, though. I'm still trying to fully understand how this type of circuit works.

analog kid-

Yeah, the Colorsound circuit would probably work with a pair of 33K resistors and the .0068uF caps as well. I do think it's important that the values are reasonably close to the schematic in the Ts for it to work as intended. The actual values used will change the sweep characteristics and the frequency response. I think the second transistor shown on that schematic is to make up for losses in the filter section, or probably to provide some amount of boost when the effect is engaged.

goosonique · July 02, 2005, 06:15:10 AM

I got one of those reissue big red enclosure type.
Yup no inductor in there and its gotta such a wide sweep- so it takes quite a bit gettting used to it !
It kinda of a pain at first but you will get the haNG of it.
Let me know if you wanna a pic of the guts or pcb . !! or any other info.

Paul Marossy · July 02, 2005, 10:21:20 AM

Quote from: goosoniqueI got one of those reissue big red enclosure type.
Yup no inductor in there and its gotta such a wide sweep- so it takes quite a bit gettting used to it !
It kinda of a pain at first but you will get the haNG of it.
Let me know if you wanna a pic of the guts or pcb . !! or any other info.

I would be interested to see all of the above.

goosonique · July 03, 2005, 11:38:06 AM

Here you go....

http://photos17.flickr.com/23260381_e3e9b53d7e_m.jpg
http://photos17.flickr.com/23260380_ee5970953e_m.jpg
http://photos19.flickr.com/23260379_d197361256_m.jpg

Sorry for the bad photos ....hope to get you better pics with another camera soon ok. The pot measures 120k one of those 'Bournes' with the left leed cut , mid to ground and the right leed to pcb all this looking from the bottom of pot ... and please ignore the 1/2 watt 2.2k resistor ...it's for the led.
The orange capacitors are 2x10k400 at each end and the middle one being 100k100 . The square one is 15nJ100 (0.015uF)... please stick to this value ... chaging it seems to kill the effect by distrupting the sweep range. Transistor BC1841. The 3 big silver radial caps are 4700 in the middle (big one) and 2200 for the smaller two.
Hope this helps.
buzz me if you any futher specific info.
Btw ... this is a nice wah... have fun building it !!

goosonique · July 03, 2005, 12:06:21 PM

Talking abt the volume drop issue ... its not that a big deal coz when i used it playing loud ... really loud !!! straight after guitar and just before a nice hot dirt pedal - it was smokin. I gave up a Vox reissue for this.. just wanted some'in differant ... :roll:
If this does become an issue for all those building one, just buffer the input ... just a bit not too hot .... ! This circuit seems a bit sensative to me any tweaking seems to spoil it so thats why i have left it as is. !!
But please do go ahead and try what you guys feel would do best .... !! :lol:
Maybe a BC549 !!?? ala BOSS ! or maybe Mr Keens J201 for those who want it hot and fat !!

Hey Paul ... thats rocket science looking at your build .... to me you are an insperation. :wink:

Paul Marossy · July 03, 2005, 12:57:24 PM

goosonique-

Thanks for the pics. Not quite what I expected to see inside. Looks like a quality PCB and components. I wouldn't exactly call that first project of mine rocket science, but I guess it's a little complex. Have you seen my second DIY wah? It's quite a bit easier to fabricate...

http://www.diyguitarist.com/DIYStompboxes/DIY-Wah2.htm

goosonique · July 05, 2005, 12:25:03 PM

No problems Paul .... btw i do have a nice piece of aluminium plate which always screams out wah-wah ... so hopefully soon after clearing my repair jobs might answer that calling. Hey nice build on your second wah.
see yas..

Paul Marossy · July 05, 2005, 12:30:16 PM

goosonique-

Thanks.

analog kid · July 11, 2005, 02:38:00 AM

goosonique,
Are those axial lead silver caps on that board Polystyrene

Might also be a crucial element to the tone of this circuit along with just values , if so?
The one I built "works" but the sweep goes to an awful extreme bass end. I used a .0082 rather than .0068 uf cap and didn't think it would matter much , but I'm wondering if those cap values (.0022, .0068, and .015) might be the most important to be ALL dead on for this thing to have a usable pleasant sweep??First I thought it was the Twin resistors that needed to be Exact but I have them at 183k each now and there's no difference at all from 120-150k in those positions.
I also wish that someone would have that layout worked out as it is in yours ! I can ALMOST see it well enough to get the layout right but I would probably need a closer shot. I really like the long narrow PCB and the way the board is populated.

cd · July 11, 2005, 09:34:49 AM

FYI the re-issue pics that goosonique posted look EXACTLY like the one I traced, so the schem I posted (see page one of thread) should match up.

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Q About the ColorSound Wah