soundsample, boomerang wah clone

[joegagan]

damn! i forgot to do a weak cheese rebop of  the voodoo chile lick. anyway, zac zagar built this boomerang a year ago, we thought it was ok, but it had a boring inductor, wrong pot, 2n5088s ( too much gain) etc. put it on the back burner.

i resurrected it, put in a 74 EL RAd inductor, specially prepared pot to duplicate the feel and sound of a real boomerang, a treble bleed mod, some old style 150 hfe transistors, upped the cap to ground to 8 uf  and BAM sounds like the real thing.

and here is a quickie hint at how the pot works:

http://smg.photobucket.com/albums/v311/joegagan/wah/?action=view&current=DSCF9214.mp4

[azrael]

whoooa, joe, that is a crazy way to rig up that pot, haha.

[Pigyboy]

Hi Joe,
Great work. Is that a 25k in there?

Chris

[joegagan]

hi chris, it is a hotpotz1, run backwards, 47k limiting resistor, with a cam to alter the taper to mimic the proper maestro feel and sound.

[bluesman1218]

hi chris, it is a hotpotz1, run backwards, 47k limiting resistor, with a cam to alter the taper to mimic the proper maestro feel and sound.

Very cool, Joe. Subbed your YouTube channel, too.

[petemoore]

   That clip has as much 'wah pronunciation' as any I've heard, and is clean/thick also...very nice !
   Have used the cam-pot trick and +1 recommend as it has achieved primary goals where circuit-bending fails or has difficulty to go to, {also ''bending a circuit-fragment generally involves 'the other parameter[s' changing too.

[Paul Marossy]

Viva la Boomerang!!!!! 

[joegagan]

update,

zac and i made a direct comparo between a BG1 67 and a bg2 74. quite telling. simple test, just open string strum.

[joegagan]

another famous boomerang song, jj cale. check out his masterful  and restrained use of the wah. he finds the distorto spot on the low end and just rides it like a voice.

all good boomers i have heard have the same distorted growl at the low end. tons of character. very different from the  CB/vox voicing. IME it would be very difficult to mod the CB into this sound. the whole thing about the  boomer is the circuit is desigend around the 25kpot, plus there are no 470k mix resistors, the two stages have independent bias.

[John Lyons]

Nice song / wah tone.
That one's right up your alley Joe (with this low end growl kick your on/after).
Seems like he's really got a resonant peak going on there.
When he hits that one spot it really ramps up the gain and quacks.

[Paul Marossy]

I actually like the BG-2 a little better, sounds a little thicker/smoother to my ears.

J.J. Cale uses that wah pedal so it sounds like a slide... pretty cool! 

[joegagan]

wow, paul thanks for listening.  people surprise me, i always think people like what i like but i constantly am reminded how different we all are. it makes a lot of the things said at the cork sniffer forums seem a little quaint when you remember how subjective it all is.

i totally prefer the  BG1, but it is possible that the sound in the room was more dramatic. zac agreed, he liked the more harmonically rich sound of the BG1. it has a slightly wider range ( more treble?) and a seemingly sweeter fuller sound at all points of travel to my ears.

next to test is to return the 74 to the inductor it came with new , el rad , baby. then we can do same test, same room/cam location, same guitar and amp/vol levels. will do exact same test to see if the inductor gets closer to the 67 sound.

on crazy mama, i think jj cale was also using a slide. wah and slide together can be an amazing thing.

[Zzagar]

I have to agree with Joe Gagan, the BG1 just has just a little extra pronunciation and a little sweeter sound (at least in person it is pretty darn noticeable) that cant totally be copped by the BG2.  I'm always amazed everytime I hear the BG1 (as the pedal is usually stored at Joe's house) it has just a very mellow but specific sound.   Between the two of us, we have tested MOST if not all, of the 'solutions' for mimicking the 25kA pot.  As far as getting to the value (i.e. limiting resistors, etc) not really a problem, as far as getting the taper, I sometimes feel as though I'm banging my head against the wall, looking at the wall, and asking why does my head hurt?!?!? 

[Paul Marossy]

wow, paul thanks for listening.  people surprise me, i always think people like what i like but i constantly am reminded how different we all are. it makes a lot of the things said at the cork sniffer forums seem a little quaint when you remember how subjective it all is.

i totally prefer the  BG1, but it is possible that the sound in the room was more dramatic. zac agreed, he liked the more harmonically rich sound of the BG1. it has a slightly wider range ( more treble?) and a seemingly sweeter fuller sound at all points of travel to my ears.

next to test is to return the 74 to the inductor it came with new , el rad , baby. then we can do same test, same room/cam location, same guitar and amp/vol levels. will do exact same test to see if the inductor gets closer to the 67 sound.

on crazy mama, i think jj cale was also using a slide. wah and slide together can be an amazing thing.

I use fairly bright high-er output pickups that have lots of harmonics. They don't sound good into a bright wah, makes things way too harsh for my taste.

So J.J. was using a slide. Interesting combo that I don't think I've heard until this morning.

[azrael]

i like the BG1 better, FWIW.

[Gus]

Something to help tune this type wha.

 Note the operating point changes with two resistor values.

 By adjusting two resistors you can use different transistors.

 I am not a fan of the bias used in this type wha.

Takes about 5 min to draw and sim.  I picked two different transistors from the stock LT spice install 2N2222 and 2N5089



EDIT Mistake in schematic R 6 should be 4.7k

I posted the schematic to show what two resistors I would  adjust to change the transistor(s) operating points(bias)
The higher the hfe the higher the resistor values for the same operating points

Question I have not used or seen a boomerang wha, is the schematic correct? it was drawn from the Phillip Bryant one on the web

[joegagan]

thanks gus, we've got one on the breadboard right now as well. we will build it with your values. so far, i had attempted to strike a midpoint in values between the boomerang and CB/vox we were attempting to make a 100k pot work better with it. using a stock boomerang topography we found the biggest factors to be Q1 bias, the 1.0 caps around the pot, the 4.7k  R at Q1 collector in loop, and the .01 Q cap.
we will let you know how yours  biases up.

[Gus]

The cap from Q1 collector to the "top" of the wha pot is a tuning point for a few reasons

One when the wiper is at the "top" of the pot the gain stage is loaded more, 25K in parallel with 10K (the bass end)  At the treble end there is more series resistance between the collector and the wiper of the wha pot
Two the cap size can adjust how much of the lower frequency signal passes to the EF because of the resistance values, RC filter stuff
The size affects both the loading of the first stage and RC time constant  and drive to the EF

Lower value resistor at Q1 with bias adjusted for same collector voltage, lower gain BUT better drive(lower output resistance)

I would try film caps from  .22uf to 1.5uf for the in to the wha pot  cap

[joegagan]

The cap from Q1 collector to the "top" of the wha pot is a tuning point for a few reasons

true, we noticed that cap was particularly active in voicing the pot. we tried all sorts of values for both 1.0 spots. .47, .22, .33, 1.0 but  nothing above 1.0. different combos. i started getting confused we tried so many.

noted your entire post. will print out your info for the next round of speriments. appreciate the help!

[Gus]

Changing the 6uf cap value changes things in the sim

In the sim at about 1uf things change raising the freq and narrows the Q however you can bring it back down with adjusting the sweep cap

In the sim at the higher frequencies it adjusts how much of the lows are still in the output 1uf less lows 6uf more lows with the resonance frequency

I would try a 1uf film for C5 with a switchable cap(s) in parallel

Making C5 smaller works somewhat like adjusting R6

Adjusted values schematic


IMO using  LT spice can be helpful in tuning a wha.