Let's talk wahs

[tackleberry]

Pots question. ICAR vs hot potz? In searching some say the true ICAR taper pot is the way to go, and easy enough to find about 17$. And there are some that you just need a good audio pot designed for long life like the hot potz, again easy to find a little more money. Is it going to be more of a subjective difference that either is good and just a little difference in tone, not bad difference just different. My old crybaby Ive modded recently has the original blue body dunlop made in mexico pot, any info on those? I got an offbrand wah off fleabay yesterday and when I opened it up it just had a cheap generic 16mm audio pot, gonna imagine that aint gonna last long. I bought it for the housing more than anything tho. Someone asked how the eleca inductors sound. I bought a batch of 5 from smallbear, much cheaper that way. Ill see how they sound in a few days. 

[Mark Hammer]

Joining this thread a little late.

You know, it may be heresy, I don't think it makes a tinker's dam worth of difference what transistors you use.  Personally, I think many of the claims people are making here are misattributions resulting from serendipitous pairings of resistor values and transistor properties.

Why do I say this?  I built my wah from a Crybaby schematic.  May have used 2N3904 or MPSA18.  Can't remember.  What I DO remember is that it sounded awful.  Wimpy,  No range.  Too much bass.  Then I read a post about the emitter resistor on the first  transistor, the need for the gain to be adjusted right, and started to tinker with that value.  Boom-chicka-wow-wow!  It sprang to life.

So yeah, if you are simply sticking with fixed passive components on the board, and you keep shoving transistors into a socket until you get something that suits the fixed components and sounds nice, it WILL seem like some transistors are better than others.  But if you pick just about any two NPN trannies, and tweak the appropriate resistor values, you should be able to get your Ulysses telling tales in short order....as long as you're standing in a white room and no one is giving you the shaft, my voodoo child.

[MohiZ]

I just got a 2005 CryBaby. Is the stock inductor any good in it? I have a yellow Dunlop Fasel inductor, so I can expect it to sound better than the stock one?

NOTE! I know this is a subjective thing.

[slideman82]

You know, it may be heresy, I don't think it makes a tinker's dam worth of difference what transistors you use.  Personally, I think many of the claims people are making here are misattributions resulting from serendipitous pairings of resistor values and transistor properties.

Right, it's not the same as in a FF, but I think higher gain ones make the wow-wow more present... or probably is juast a matter of bias...

[MohiZ]

Then I read a post about the emitter resistor on the first  transistor, the need for the gain to be adjusted right, and started to tinker with that value.

How about the second transistor? Has anyone tried tweaking that?

[Gus]

I been marking up schematic of whas

Some thoughts.  Mostly about transistor operation points in three different whas

Crybaby like first
Q2 in the two transistor crybabay like circuit should not matter all that much with high enough hfe.
  Why?
  One it is an emitter follower input R ~= hfe x emitter R so lets take a hfe of say 200 x 10,000 = 2,000,000 or about 2 meg, if hfe is higher input resistance is higher.
  Two the transistor is biased via the 470K from the first transistors collector if the higher the hfe the lower the voltage drop across the 470K because of less base current needed.  R.G. writeup has this stuff in it.
  Three less loading on the pot and Q1 collector the higher the hfe of the transistor
  I would use a high hfe at Q2 and not worry to much

Q1  in a crybaby should not make much difference again if hfe high enough (please keep reading) a 22K collector resistor and 390 ohm to 510 emitter set most of the open loop gain BUT the bias is set by the voltage divider bias network of the 470K from the collector to the "top" of the cap and 82K etc resistor, then you have the DC resistance of the inductor and parallel damping resistor and 1.5k resistor to the base.  The voltage at the node of the 470K, 6uf on up electro, inductor and 82K and the series resistance from that node to the base is what is setting the bias for BOTH transistors.  SO adjust the voltage divider for the TWO TRANSISTOR OPERATING POINTS.  I would adjust the 82K because it is bypassed but the electro cap and is at a DC voltage but an "AC ground".


So for a crybaby build I would use >200 hfe and adjust the one 82K resistor value to bias the two transistors to taste.  I would use a high hfe for Q2.

Now when you look at the Boomerang it looks different.

Boomerang

The bias for Q1 is different a voltage divider is not used.  Open loop Q1 gain partly controlled by the 10K C and 120 ohm E resistors.  Bias set by the series resistance of the 1.5meg and (inductor and damping resistor 47K in parallel) and 4.7K from collector to base of Q1.  Again the end of the inductor and 47K and 1.5meg are at "AC ground" if the cap has a high enough value.  In this case adjust the 1.5meg,  Q1 hfe will be more of an issue than the crybaby bias IMO need to think about this some more.
A bigger difference is the bias of Q2 it is not biased via the collector of Q1 and a resistor.  It is biased via a resistor C to B and the input resistance is hfe x 8.2K in parallel with the collector to base bias resistor.  Different C to B resistor value should give different emitter to ground operation points.

Q2 will matter because of the bias used.

  If one was the use the crybaby Q2 with the the 470K another thing changes the 470K lets more signal pass via the 470K and there is the signal from the wiper of the wha pot.  In the boomerang the signal comes only from the wiper of the wha pot to Q2

Q1 will matter a bit BUT if you get in a hfe range you can control the bias with changing the 1.5 meg resistor value.

Colorsound

Colorsound more like the crybaby except for the use of the grounded emitter open loop gain stage at Q1 and no damping resistor across the inductor.  I would use a high hfe at Q2 and Q1 I need to think about some more.  Q1 bias and Q2 bias again can be controlled via adjusting the 100K resistor value

[kierc]

Almost done with my Boomerang now 

This may be a silly question - but how do you wire it up?  (With a DPDT foot, and a SPDT toggle for wah/vol)

lol just can't work ym brain  lately!

[Paul Marossy]

Almost done with my Boomerang now 

This may be a silly question - but how do you wire it up?  (With a DPDT foot, and a SPDT toggle for wah/vol)

lol just can't work ym brain  lately!

The stock circuit uses a SPDT switch. If you wanted to wire it true bypass, you would have to add another switch to select between wah & volume modes.

In the stock circuit, the "bypass" switch basically just takes the 6uF cap in or out of the circuit.

[biggy boy]

Thanks to Paul Marossy's excellent site on Wah Mods for the information.

If I'm OK to post a link, it's here...

http://www.diyguitarist.com/DIYStompboxes/WahMod.htm

  I used that website, almost two years ago to mod two crybabies. Found it googling one day.
I just made the connection of who's site it is !!

Thanks Paul for providing it, it was and still is the best one to use.

Glen

[Paul Marossy]

Thanks to Paul Marossy's excellent site on Wah Mods for the information.

If I'm OK to post a link, it's here...

http://www.diyguitarist.com/DIYStompboxes/WahMod.htm

  I used that website, almost two years ago to mod two crybabies. Found it googling one day.
I just made the connection of who's site it is !!

Thanks Paul for providing it, it was and still is the best one to use.

Glen

Yep, I am guilty as charged. 

Glad you got something out of my website, I'm always happy to hear that. 

[biggy boy]

As far as wahs and fuzz go.
Is there a preferred combination  order of the two?
wah then fuzz or fuzz then wah?

[kierc]

Almost done with my Boomerang now 

This may be a silly question - but how do you wire it up?  (With a DPDT foot, and a SPDT toggle for wah/vol)

lol just can't work ym brain  lately!

The stock circuit uses a SPDT switch. If you wanted to wire it true bypass, you would have to add another switch to select between wah & volume modes.

In the stock circuit, the "bypass" switch basically just takes the 6uF cap in or out of the circuit.

So the original doesn't turn off, but only switch between wah/volume modes?

I have a Carling DPDT under the toe for Bypass, and I've also got an SPDT toggle I'd like to use for wah/vol modes - but the image of the switch for wah/vol is layed out like a footswitch and that's confusing me on how to wire to toggle, and then to have the Carling for Bypass?

(I'm really sorry by brain is so dead lately  )

[Paul Marossy]

So the original doesn't turn off, but only switch between wah/volume modes?

Correct.

I have a Carling DPDT under the toe for Bypass, and I've also got an SPDT toggle I'd like to use for wah/vol modes - but the image of the switch for wah/vol is layed out like a footswitch and that's confusing me on how to wire to toggle, and then to have the Carling for Bypass?

Just wire it like any other true bypass pedal. Add a SPST switch to for volume/wah mode. It would be more clear to you if you look at the schematic here: www.diyguitarist.com/PDF_Files/BoomerangBG2PCB.pdf

[kierc]

Cheers for all your help Paul 

Think I'm gonna leave it as the original with the footswitch as the vol/wah, and perhaps add a switch to disconnect the battery,

I've had a look at the schematic and the diagram again - would wiring up the DPDT like this work? Or have i got the two wires messed up??(I think I have now I look at it again lol)
(sorry for crudely 'shopping your image! )


Sorry again 

[Paul Marossy]

Yes, that would work, but it's not true bypassing the pedal. Is that what you want?

[kierc]

Cool, cheers 

I just want it working first and see how I like it before I go changing things - just waiting for my damn transistors to come!!  lol

[jakehop]

For what it's worth, I did some measurements on my old 70's CryBaby with Stack-o-Dimes inductor.

Besides using CC-resistors all over, and a HotPotz 1 100K potentiometer, Q1 had a hFE of 395, the inductor measured 598mH with a 45 ohms resistance, the caps were all metal film, and the electro was a 3.9uF tantal.

I'll get back when I research some more.

Kind regards, Jake

[ayayay!]

The only time I've found high gain trannies like MPSA18s to really help out is when your inductor is weak.  Helps to boost the output just a wee bit to use those trannies, but again I'm only talking about when using it in conjunction with a weak inductor.  It would be better to just use a better inductor, and use the trannies of your choice.

So are you measuring Henries with a meter guys?  Or are you doing the old, "run a 1khz sine through and test resistance and whatever else formula" to determine mH?  I'm looking for a *cheap* meter to measure inductance.  Any links are appreciated.

On a side note, I'm picking up a broken wah from a guy today that has the whole Whipple kit installed.  I don't care about the rest of it really, but since a Whipple inductor alone is $23.00 and the wah is going for $25.00...  I want that 100k ICAR pot too.    I'm not much of a "throaty" sounding wah guy.  I'm happy with a standard Dunlop inductor, if it's the right one.  They can be spotty, but they're not as bad as people make them out to be.  Between that wah and mine, and my wife's grandpas with the TDK inductor, I'll have quite the array of Crybaby's handy. 

[kierc]

Well I got my BC109's today and got to finish off the Boomerang    (posted a picture in the relavant thread!)

It works fine - it wahs and it volumes (both from the footswitch), but it has this ghastly clicking at certain points of the treadle/pot rotation? and it's reaallly loud and so unuseable as it is..

I made a quick shoddy video which you can hear what sound I'm talking about - (photobucket has a silly thumbnail size!!)



In the video I'm just rocking the treadle back and forth without playing anything, then switching to wah mode and still rocking the treadle without playing, then I play some noise so you can hear the wah behind all the clicking...

Any idea how to fix it?  The circuit is completely stock, I wired the footswitch as above, and I have an SPDT toggle in between the 9v negative to ground so I can disconnect the battery...

Really appreciate everyone's help on this site! It's amazing! 

[gmoon]

So are you measuring Henries with a meter guys?  Or are you doing the old, "run a 1khz sine through and test resistance and whatever else formula" to determine mH?  I'm looking for a *cheap* meter to measure inductance.  Any links are appreciated.

I bought an LCR meter from Hong Kong on ebay, total of ~$25 (shipping included):
http://stores.ebay.com/worldzon

Not affiliated with them. You'll probably find something similar (better, actually) in the $40-$75 range (USD.)

So far, it's worked well. I'm not wild about buying from Hong Kong, but I do have a budget. Tough to beat the price.

4 Inductance Measuring Ranges (not great for RF work, but excellent for audio):
20mH / 200mH / 2H / 20H, +/- 2.5%, + 5 digits;

(measures capacitance, too!)