Q About the ColorSound Wah

[Paul Marossy]

Well, I am 98% complete now. I just have to mount the bypass switch.  

[Paul Marossy]

OK. one last question: Does anyone else experience a drop in volume with this circuit? The bypassed signal is considerably louder than the effected signal. BTW,  I used a 2N5089 transistor. I am thinking that maybe it's due to my battery being down to slightly less than 8 volts. Any second opinions?

[cd]

I don't remember any volume drop when I had my RI, nor when I breadboarded the circuit when testing out the circuit values (see old thread).  A 2N5089 should have more than enough gain though.  If not try increasing the collector resistor.

As for pot taper - my notes only show 0-36k, but again IIRC, the pot was going through a large portion of its rotation, more than 50%.  If it was a linear pot, that wouldn't jive with the 36k range (36k in 100k linear pot is approx. 40% rotation).  If it was a log pot, 36k would be over 50% of the pot rotation.  However with the single variable resistor, you can play around with other resistors in parallel to get the taper you like, so log/linear shouldn't be a huge problem.

[Fret Wire]

Interesting. In a Vox shell, I usually adjust a Hotpotz II to go from about 25ohm to about 95k, in other words, almost full value. That sounds odd, but when you chart out the taper in the Hotpotz, you see that it has a pretty fast taper, then it hits max value pretty early (around 1 o'clock), and holds that to 5 o'clock. Same with the Hotpotz I (120k).

[Paul Marossy]

Hmm, I'll try a new battery and see what results that yields. Maybe I'll have to mess with the collector resistor value. I just thought of something - I did use a 5.6M resistor, should that have been a 3.9M instead?

[dadude]

Here's a post from Harmony-Central from a guy who has the reissue. He's complaining about the volume drop when the pedal is engaged.

"The only drawback I found was a very SLIGHT volume loss when the effect is engaged. I have found that most (all that I've played) Crybaby's and Vox's have a short throw (bad for me) but a mid-range bump (good) that lets them cut through the mix. I wish the colorsound had a variable boost-that would be GREAT!"

Maybe we can make that happen for this poor soul...

:lol:

[cd]

Shoot!  Come to think of it, changing the collector resistor won't make a difference since the emitter is already grounded.  And my transistor biasing theory is a bit hazy (OK, a lot hazy - what is this scheme called, collector feedback biasing?) but lowering the 5M9 resistor won't make any difference either.  The key is the 330k input resistor - make that a 33k (and change the .01u cap to .1u) and the volume should be boosted up BIG time.

[cd]

Also: for more volume without mucking around with the transistor, change that voltage divider on the output.  Make the 47k resistor 100k.

[Paul Marossy]

Thanks for the suggestions cd.

EDIT: Had a thought. Won't changing the input resistor and cap change the frequency response of the circuit? I think I'd be more inclined to change that 47K resistor on the output to a 100K, and maybe use a trimpot.

[cd]

Ummm... off the top of my head, provided you increase/decrease the cap/resistor in equal ratios (decrease one by 10x, increase the other by 10x, and vice versa) the frequency response should not change.  But yeah, that divider on the output is the easiest place to start (DUH which is why I thought of it second, I never think of the easiest thing first ).  There should be more than enough gain from the transistor, so you may find replacing the 100k/47k combo on the output with a 100k trimmer (or a 100k pot) acting as a volume control easier.

Again though changing that voltage divider will alter the frequency reponse (note the cap on the 100k resistor passing highs).  If you lower the value of the 100k resistor, increase the cap value.

You know, while you're in there, I'd stick another transistor in there.  Wire a 2nd transistor as an emitter follower buffer after the voltage divider (like the output of a TS-9).  The output of the stock circuit is pretty high Z and can be loaded down like a regular inductor wah.

[Paul Marossy]

provided you increase/decrease the cap/resistor in equal ratios (decrease one by 10x, increase the other by 10x, and vice versa) the frequency response should not change.

I was thinking that as I was driving back to work from my lunch break. Although this seems counterintuitive.

Again though changing that voltage divider will alter the frequency reponse (note the cap on the 100k resistor passing highs). If you lower the value of the 100k resistor, increase the cap value.

I was thinking of changing just the 47K resistor to ground at the output to a 100K. By doing so, wouldn't that just increase the output level without changing the frequency response (at least by very much)? What I am really shooting for is at least unity. I guess I really need to try a new battery first!  

[Paul Marossy]

Just for the sake of recordkeeping, last night I changed that 47K resistor on the output to a 150K. That makes the effected signal just about as loud as it is when bypassed. I think with a brand new battery it will be perfect.  I can't really say with 100% accuracy if the frequency response has shifted a little or not, but it doesn't appear to have, at least not noticeably.

I like the sound of this wah. It's a different animal than a CryBaby/Vox, though, in a good way.

[vanhansen]

Very cool.  Thanks for keeping us all updated on this, Paul.  This one is going on my "to build" list.  It looks simple enough for me at my level of experience.

[Paul Marossy]

Your'e welcome.  :wink:

These twin-T wahs are kind of fun animals. I just had to build one when I learned that you could have an inductorless wah!

[vanhansen]

Yeah, me too.  I didn't know you could have one without an inductor either.  Hopefully I'll have some time to perf this one after I finish building and boxing my two projects (Marsha Valve and Sixteen Overdrive).  Man, my setup is changing all the time now.

[Somicide]

thats a nifty enclosure!  Props on that beast; I may have to make a similar one myself...  The idea i had was to use a belt sort of set up, kind of confusing... tie one one of a string to each end of the moving portion of the pedal, then tie to seperate holes in the pot shaft, so when it moves, one winds, the other unwinds.. don't know if it'd work in practice though.

PnL,

Jeff

[Paul Marossy]

You could try it the way the original Colorsound wah was done.

The method employed on the original Colorsound wah was clever - a fixed lever is attached to the foot paddle which goes up/down into the body. There is a black plastic slotted lever connected to the pot that pivots and slides along a pin in the foot paddle lever which turns the pot.

Here is a side view: http://www.diyguitarist.com/Images/ColorsoundWah2.jpg

[Samuel]

I never thought I'd say this but this thing may have too much sweep! I'll see what the potential recipient thinks...But yeah tons more sweep than a crybaby, and mounted in a crybaby shell...This thing sounds pretty great!

Edit: on second thought, maybe my crybaby ain't quite right - in any case thumbs up on the CS....

[analog kid]

Does anyone have a practical layout done for this schem that they wouldn't mind posting?? I am not great with making them , even with a simple and small crkt like this but probably could do with a bit of time. Just thought It would be easier to see one that someone else uses to give me a 'template ' to go by or use.
thanks

[Paul Marossy]

analog kid-

This is the PCB layout that I created when I built mine:
http://www.diyguitarist.com/PDF_Files/ColorsoundWahPCB.pdf