Let's talk wahs

[Wales]

increasing the resistor increases the Q

right sorry I was thinking backwards. I knew the voltage to the collector needed to be less, I don't know why I though lowering a resistor value would decrees voltage (Exact opposite) My heads back on straight now.

[Paul Marossy]

I have a lot to learn about modding wahs, but even more importantly, I do not know what a really great wah sounds like!!! Can someone provide a great example of a really "vocal" wah?? I mean, when great wah tones are described, what songs are people talking about?

The theme from "Shaft" is a Maestro Boomerang. That is still my favorite wah pedal, and I have built a lot of different wah circuits now. I like it because it's vocal sounding, fat sounding and it's not shrill. I have several CryBabys and many of them are modded, but I don't really have any of them on my pedalboard ever. The only exception is my wah pedal with a TDK5103 inductor in it. Everyone says they sound terrible, but I think this one sounds really good. I prefer it over all my other wah pedals, except for the Boomerangs that I have.

IMO, what inductor you use is indifferent. There's a lot of other variables to consider besides just the inductor. And which kind of caps you use I think is in the same category, too. In fact, my least favorite wah pedal is my Vox wah with an original Fasel inductor in it - it's just too thin and shrill sounding, I can hardly stand using it... 

[kierc]

I have a spare red fasel inductor, and i'm not really amazed by my Clyde McCoy clone, and was thinking about building the Boomerang with your layout, but how do I get a 25K pot with a gear on it??

I have 2 spare wah pots, but one is 100k and I think the other is 100k too...

[Paul Marossy]

I have a spare red fasel inductor, and i'm not really amazed by my Clyde McCoy clone, and was thinking about building the Boomerang with your layout, but how do I get a 25K pot with a gear on it??

I have 2 spare wah pots, but one is 100k and I think the other is 100k too...

Ernie Ball makes a 25K pot. You can buy the Dunlop rack & pinion gears from places like www.tubesandmore.com
You might have to modify the pot a little bit to make it work, but it can be done. I've done that once before...

[B Tremblay]

The easiest approach is a 33k resistor in parallel with the 100k wah pot.  At least you can then determine if you like the circuit without investing time and money in the 25k pot.

[kierc]

Pardon my un-knowing-ness, but where would I put the resistor??
Across the 2 outer lugs?

Thanks!

[B Tremblay]

Yes, between the outer lugs.

[kierc]

Nice one, cheers! 

Just etched myself 2 of the boards on Paul's site 

[Paul Marossy]

Nice one, cheers! 

Just etched myself 2 of the boards on Paul's site 

Cool! Enjoy... 

[jrod]

increasing the resistor increases the Q

right sorry I was thinking backwards. I knew the voltage to the collector needed to be less, I don't know why I though lowering a resistor value would decrees voltage (Exact opposite) My heads back on straight now.

The wah that was used on the Shaft soundtrack is in the STAX museum in Memphis. They say it is THE one used and, IIRC was a Boomerang 2. I don't think it was the original Boomerang, but I could be mistaken. Anyway, I thought that was really cool to see there.

[Paul Marossy]

increasing the resistor increases the Q

right sorry I was thinking backwards. I knew the voltage to the collector needed to be less, I don't know why I though lowering a resistor value would decrees voltage (Exact opposite) My heads back on straight now.

The wah that was used on the Shaft soundtrack is in the STAX museum in Memphis. They say it is THE one used and, IIRC was a Boomerang 2. I don't think it was the original Boomerang, but I could be mistaken. Anyway, I thought that was really cool to see there.

The Boomerang 2 is the same circuit as the original Boomerang. It just has a couple parts added to make it double as a volume pedal.

[B Tremblay]

Check out this message for some mods I did to my build of the Boomerang (including schematic and clips):
http://www.diystompboxes.com/smfforum/index.php?topic=52412.msg396085#msg396085

Paul has been a Boomerang evangelist for quite some time now!

[Bender]

Anyone try the eleca inductor on small bear's site? Been curious about that one..........

[kierc]

Sorry for another silly question... but what transistors would you recommend for the Boomerang?
I know Paul's schema states BC109...

I have some gold pin BC109B's I pulled from my McCoy clone - if they still work! can't seem to get a hfe reading from my rubbish DMM... (they were soldered, not socketed)

[jrod]

increasing the resistor increases the Q

right sorry I was thinking backwards. I knew the voltage to the collector needed to be less, I don't know why I though lowering a resistor value would decrees voltage (Exact opposite) My heads back on straight now.

The wah that was used on the Shaft soundtrack is in the STAX museum in Memphis. They say it is THE one used and, IIRC was a Boomerang 2. I don't think it was the original Boomerang, but I could be mistaken. Anyway, I thought that was really cool to see there.

The Boomerang 2 is the same circuit as the original Boomerang. It just has a couple parts added to make it double as a volume pedal.

Oh, ok. Thanks for that info, Paul! 

[Gus]

Paul  I just looked at your boomerang pages. Nice write up

   The 860k or 680k collector to base resistor sets  DC bias of the 2nd stage.  Q2 being used as an emitter follower with a 8.2K emitter resistor.  Now if people want to try different transistors at Q2 maybe make the C to B transistor a 470K fixed with a 500K pot to find the value that you like and sub a fixed one in close to the measured value of the 470K and 500K pot setting

Q1's bias is partially set(C and E resistors as well) by the stuff in the C to B path one one part that might be the one to adjust (that does not upset the circuit too much) to get the bias of Q1 to what you want would be the 1.5meg maybe try 1.2meg to 1.8meg resistors or a fixed 1meg and a 1meg pot.

The easiest way might be to measure the Q1 collector and Q2 emitter voltages in the wha you like and then adjust the two resistor values to what you like in a new build, OR measure the hfe like you did to preselect transistors to work with the bias resistor values you like.

EDIT  also 1uf 25K 1uf compare to .22uf 100K .22uf.

[slideman82]

My doubts: why there is a 1k resistor from 9V? Probably is a filter... is just that? And what effect does the .33uF instead of .22uF in the whiper?

[Gila_Crisis]

EDIT  also 1uf 25K 1uf compare to .22uf 100K .22uf.

do you mean that the boomerang pot arrangement is "equal" to the standard crybaby/vox one?

[kierc]

hmm can't edit my post...

Any good sources for an axial 6uF cap for the Boomerang?

[Paul Marossy]

Check out this message for some mods I did to my build of the Boomerang (including schematic and clips):
http://www.diystompboxes.com/smfforum/index.php?topic=52412.msg396085#msg396085

Paul has been a Boomerang evangelist for quite some time now!

Yeah, I'm a believer. 

Sorry for another silly question... but what transistors would you recommend for the Boomerang?
I know Paul's schema states BC109...

I have some gold pin BC109B's I pulled from my McCoy clone - if they still work! can't seem to get a hfe reading from my rubbish DMM... (they were soldered, not socketed)

You can use a lot of different transistors in this circuit. I used 2N3904s in another one I built.

Paul  I just looked at your boomerang pages. Nice write up

   The 860k or 680k collector to base resistor sets  DC bias of the 2nd stage.  Q2 being used as an emitter follower with a 8.2K emitter resistor.  Now if people want to try different transistors at Q2 maybe make the C to B transistor a 470K fixed with a 500K pot to find the value that you like and sub a fixed one in close to the measured value of the 470K and 500K pot setting

Q1's bias is partially set(C and E resistors as well) by the stuff in the C to B path one one part that might be the one to adjust (that does not upset the circuit too much) to get the bias of Q1 to what you want would be the 1.5meg maybe try 1.2meg to 1.8meg resistors or a fixed 1meg and a 1meg pot.

The easiest way might be to measure the Q1 collector and Q2 emitter voltages in the wha you like and then adjust the two resistor values to what you like in a new build, OR measure the hfe like you did to preselect transistors to work with the bias resistor values you like.

EDIT  also 1uf 25K 1uf compare to .22uf 100K .22uf.

Good suggestions. I bet that the 1uF 25K arrangement is roughly equivalent to the .22uF 100K arrangement in terms of sound.

My doubts: why there is a 1k resistor from 9V? Probably is a filter... is just that? And what effect does the .33uF instead of .22uF in the whiper?

I don't think that changing those caps from 0.22uF to 0.33uF would make much of a difference in the sound. What will make a big difference is the value of the sweep cap.