Schaller Bow Wow - Yoy Yoy rebuild.

[digi2t]

Hi all,

I bought this wah about 2 years ago, but was never really impressed with it. The wah (bow-wow) setting was weak at best, and the Yoy setting was down right anemic. I was dissapointed, to say the least. So, while waiting for parts for other projects, I decided to have at this sucker. This is the original schem (corrected) that I found on the net;



For the most part, it was correct, but I made some corrections to it to reflect exactly was was in mine. Initially, I just started playing with cap values here and there, trying to up the effect. Finally, I decided to start from scratch. I started with the trannies. Being a real BC109C fan, and having a pile on hand, I swapped these in, replacing the BC109B's.

I then ditched the carbon resistors, and went for metal films. Three resistors were sub'd with trimmers. One for adjusting the voltage on Q1, another to fool around with the midrange (this is a Crybaby mod, but I found it works here), and another to be able to balance the output level. I found the last one necessary, since playing with the voltage of Q1 has a direct impact on the output volume of the pedal between "IN" and "Bypass".

The pot in this was not a reverse linear, as is stated in two different schem versions I found. Mine was just plain linear. I don't know if this was original or not, but the pot looked pretty old. I ditched it for another linear, but I still didn't like the "feel" of the sweep, so I tried a regular log pot. The log pot was much better. I sealed the deal by adding a 120K resistor across the 2 and 3 legs of the pot, which smoothened out, and shifted the taper just a bit more to my liking. In any case, pots in a wah are really a personal thing, so one persons garbage, is anothers gold. This works for me.

Finally, the caps went "bye bye". I had a pile of 10uF tantalum caps kicking around, so they went in. The 10uF on the positive rail got replaced by a 220uF, since I might run this on a power supply. Then I started auditioning possible replacements for the other caps. In the end, this is what I finally settled on;



Some gut shots;









It sound much throatier now in the wah mode with dirt, than it did before. It's got a lot more punch. In yoy mode, it reminds me quite a bit of the Mr. Multi in phase mode, or the Phase II in parallel mode. Of course, I know my bro Jimi wouldn't let me off the hook that easy, so, the mandatory video. Dirt pedal is an Uglyface;

There you have it. No Mold Spore, for sure, but much better (IMO  ) than the lethargic stock trim. I also noticed that these things would make neat looking ashtrays, upside down, on a table, next to a nice Tiffany lamp. Play it again Sam...

Cheers,
Dino

[Mark Hammer]

I used to have one, and the Yoy-yoy sound was delicious.  Possibly the best recorded version of it I have ever heard was the Manu Dubango afro-beat hit "Soul Makossa".  I can't see the drawings you posted, or listen to the video, but look forward to seeing if they nail what I loved about the pedal.

[digi2t]

Well, from what few videos and clips I've seen and heard, I "stole from Peter to give to Paul" in this case. It's a really fine balance between the wah and the yoy cap wise, but in the end, I opted for more emphasis on the wah. The yoy was just not doing it for me. Going with the bigger caps really beefed up the wah portion. As for the yoy, it's more of a "wayouuu" sound now when played clean. With dirt, it's more phaser sounding.

Let me know what you think.

[Paul Marossy]

I think it sounds great! 

[Chugs]

Nice. I've had one of these sitting around for a while that needs the switch replacing. The thread has inspired me to fire up the soldering iron.

[digi2t]

Well, I'm certainly glad that it pleased, or motivated, someone  .

I've been on a bit of a wah binge of late, and the learning curve has been wonderfully steep  . Lots of fun.

Chugs, are you going to retrofit a standard 3PDT stomp switch here?

[joegagan]

it is so cool that you have applied your smithsonian-level archeological approach to this.

after years of testing, i have come to the conclusion that linear tapers in gear driven wahs do not capture the possibilities of the circs. hence the mfgr spec'ing of non-linear pots in nearly all production wahs we can think of.       i strongly suspect that your wah has a replaced pot, or a poorly spec'd replacement pot by the maker. limiting resistors to simulate other tapers have limited or near zero effect in correcting this problem in my experience.

before making any other cap conclusions ( the cap to ground is integral to the taper ), i would suggest sourcing a pot that closely matches an original as per the noted schems.

[Chugs]

I have a spare 4dpdt that I am going to use.

[digi2t]

it is so cool that you have applied your smithsonian-level archeological approach to this.

Joe, there's absolutely nothing scientific going on here, believe you me. Just a noob putz'n around with a pedal. I just always try to share everything I find, good or bad. Figured it's the least I can do in return for all the fine help I've received here, from some fine people (your company included).

after years of testing, i have come to the conclusion that linear tapers in gear driven wahs do not capture the possibilities of the circs. hence the mfgr spec'ing of non-linear pots in nearly all production wahs we can think of.       i strongly suspect that your wah has a replaced pot, or a poorly spec'd replacement pot by the maker. limiting resistors to simulate other tapers have limited or near zero effect in correcting this problem in my experience.

You're absolutely correct. Going with the law of averages, two different schematic, both stating rev. Log., I would say that a rev. Log. should be in there. A lot can happen in 40 years, so yes, the original pot may have been swapped out at some point. Or, it was a "Friday production", and stock was short, but the war had long been over, and the Germans were really back on their feet at that time.
Correct again on the tapering resistors. I've messed around with them as well, and generally, with very limited (or no) success. In 99% of cases, I end up going with what was spec'd, 'cause hey!, there's a lot of folks out there that are way smarter than me. But, there are instances (like the Ludwig Phase II) where it can serve a purpose. I'll state again, for the record; I like the taper now. The resistor suits my feel. No guarantees, implied, expressed, or otherwise.

before making any other cap conclusions ( the cap to ground is integral to the taper ), i would suggest sourcing a pot that closely matches an original as per the noted schems.

A rev. Log. pot has been ordered. I also tried some "traditional" wah pots, a Fulltone, and a Hot Potz, but they didn't do it for me. Good thing that solder isn't permanent. Part of what makes this hobby so damn interesting.

As always, I appreciate your input Joe. Thanks for chirping in here.


 

[Mark Hammer]

Swept bandpass filters are intended to simulate vocal expression with a non-vocal input signal.

Let me repeat that another way.  They aren't intended to mimic a voice, in the sense of sounding "just like" one, and they aren't using anything remotely voice-like to do it with.  They are intended to use the varying of spectral content in an expressive way, similar to the manner in which we vary spectral content in our voices to accomplish expressive and communicative goal, using one of the least emotional expressive parts of our body that happens to be available: the foot.  I know that sounds high-falutin' and all, but let me hold up at 2nd base for a bit before you tag me out.

What this implies, when it comes to wah pots, is that:

a) Since the spectral content to be modified will vary from guitar to guitar, or rather from signal to signal, the portion of the spectrum that the user/player needs to zeroin on to accomplish their goals will vary.  Few fixed/predefined relationships between resonant frequency and pot position will satisfy all potential players.  Some might arrive at a happy medium for more players than others, but there is no real "ideal" wah pot or taper that all will agree on.

b) The translation of emotional inflection from what the player is thinking about their mouth doing (since they ARE fundamentally, even if unconsciously, attempting to "talk" through the wah) into something their foot can do in conjunction with the filter and the pot connected to it, is difficult and awkward.  Think about the entire arc of foot movement.  Where do YOU have the greatest nuance of foot movement?  Think about your hand for a moment, and try this exercise.  Imagine conducting an orchestra with your hand in a fixed position, using only your thumb or your index finger.  Okay, now try it using  only your pinky.  For most, there will be a big difference in capacity for nuanced movement.  The same is true when it comes to our feet.  It is the wah pot's role to help translate that point or range in our foot's movement, where the greatest capacity for nuance lies, into the most degree of control over the sonic parameter of interest.

[digi2t]

Swept bandpass filters are intended to simulate vocal expression with a non-vocal input signal.

Let me repeat that another way.  They aren't intended to mimic a voice, in the sense of sounding "just like" one, and they aren't using anything remotely voice-like to do it with.  They are intended to use the varying of spectral content in an expressive way, similar to the manner in which we vary spectral content in our voices to accomplish expressive and communicative goal, using one of the least emotional expressive parts of our body that happens to be available: the foot.  I know that sounds high-falutin' and all, but let me hold up at 2nd base for a bit before you tag me out.

What this implies, when it comes to wah pots, is that:

a) Since the spectral content to be modified will vary from guitar to guitar, or rather from signal to signal, the portion of the spectrum that the user/player needs to zeroin on to accomplish their goals will vary.  Few fixed/predefined relationships between resonant frequency and pot position will satisfy all potential players.  Some might arrive at a happy medium for more players than others, but there is no real "ideal" wah pot or taper that all will agree on.

b) The translation of emotional inflection from what the player is thinking about their mouth doing (since they ARE fundamentally, even if unconsciously, attempting to "talk" through the wah) into something their foot can do in conjunction with the filter and the pot connected to it, is difficult and awkward.  Think about the entire arc of foot movement.  Where do YOU have the greatest nuance of foot movement?  Think about your hand for a moment, and try this exercise.  Imagine conducting an orchestra with your hand in a fixed position, using only your thumb or your index finger.  Okay, now try it using  only your pinky.  For most, there will be a big difference in capacity for nuanced movement.  The same is true when it comes to our feet.  It is the wah pot's role to help translate that point or range in our foot's movement, where the greatest capacity for nuance lies, into the most degree of control over the sonic parameter of interest.

Mark, a great big "THANKS" for putting that so eloquently.

Point a), in my opinion, is a real crux for me. I currently have 9 different wahs in my arsenal, 4 of which are part of digital multi-effects (i.e. Boss GT-PRO, GNX-3, etc.). We compose our own music, mostly instrumental, and creating "soundscapes" is a real Holy Grail quest for me. Although the digital wahs do provide some limited flexibility in their setup, they remain just that, limited. Sometimes they're hot, sometimes they're not. Ananlog wahs on the other hand, will always offer their "entire guts" to modification. The sweep being an important one for me, since sometimes I have to switch from one wah to another. If I can take the variable of having to adjust my foot to the sweep of the wah out of the equation, then so be it. I understand that there's always a certain price to pay, so yes, I do have to compromise at times, but I can live with "close". Which brings me to point b)...

That is EXACTLY what we're (at least I am) trying to do here; Make the guitar "talk". Since I consider music a language, and all languages are expressive, I consider the wah merely a tool in assisting to amplify that expression. One should also consider that there are many, many languages on this planet. Being of Greek heritage (like the Italians as well), I consider the wah like the "hands waving" (amplifing?) part of the conversation  . Even then, we must remember, that some sort of "hand waving" in one language, may not necessarily symbolize the same meaning in another. 9 different wahs for me, is like 9 different "dialects" of the same language; Music. Whatever modifications that one needs makes to achieve a particular "dialect", or "inflection", is fine by me. I can embrace that, since I know that the quest will always be noble. Even then, I still find myself contorting some part of my body when I'm working a wah. I guess that makes up for the "close" part that I mentioned before. Sort of like telling someone to "F" off, AND shooting them the bird. 

I know that sounds high-falutin' and all, but let me hold up at 2nd base for a bit before you tag me out.

Not even close for a tag neighbour. That was a solid ground rule double.

[Buud--Buul]

Hi,

even seeing, that this a very old thread, I realized, that the shown schematics are not correct- The inductorcoils are not 500mH, first one -L1- is around 1,7H, second one -L2- is approximatly 330mH.

I just stumpled over this thread after I used my Schaller Yoy Yoy again after it has spend years stored in my closet. And I was also not satisfied with the sound.
So thanks, Dino for starting this topic and giving all the information, how you did it.

My Schaller is a MK II with plastic enclosure in hammertone finish and the main difference to the one with metal enclosure is a double 100k poti.
Surprisingly the poti is markes as 1M-pot, but measures, it showed around 133k at each poti.

I changed all the old caps and some of the restistors, that showed too differend value from what the should be. I again used carbon comp. resistors to keep some of the old still sound.
Even this pedal is already true bypass, I installed a 3pdt-footswitch adding a status led.
Little bid tricky, because the original footswitch has a longer shaft, so you have do install a (second) spacer rubber or something equal below the moving pedal part of the enclosure.

For more sarisfying "yoy yoy", I first changed the L2 inductor to a old Dunlop standard 500mH inductor - no real improvement.
Then I reinstalled the original L1 and put the Dunlop 500mH coil on position L1. And that was the tweak to make the pedal sound !!!

I also reversed the left & right joints ( CW & CCW) of the volume poti, so the sound is on maximum volume, when switched off.

At the tdpri-forum I found a question, what to do, if the double poti is broken or scratchy.
As far as I can see, one can also install every single wahwah poti, only the volume funktion isn't given then anymore.
Which is not the worst, because as every Wah/Volume pedal I know, also this Schaller Yoy Yoy sucks tone and volume.
An alternaitive to keep the volume control might be to use the 3pdt-footswitch (or, if you want also a led, a 4pdt-footswitch) and install a "groundlift" to the pcb.
That's the way it could be done with Dunlop-style wahwah and as I saw from Dino's picture here at the start of the thread, the first series with the metal enclosure aso uses a single potentiometer.
But this is more a guess and not a verified idea.

Thanks for watching and all the best to all you DIYers,

Buud

[digi2t]

Hi,

even seeing, that this a very old thread, I realized, that the shown schematics are not correct- The inductorcoils are not 500mH, first one -L1- is around 1,7H, second one -L2- is approximatly 330mH.

I just stumpled over this thread after I used my Schaller Yoy Yoy again after it has spend years stored in my closet. And I was also not satisfied with the sound.
So thanks, Dino for starting this topic and giving all the information, how you did it.

My Schaller is a MK II with plastic enclosure in hammertone finish and the main difference to the one with metal enclosure is a double 100k poti.
Surprisingly the poti is markes as 1M-pot, but measures, it showed around 133k at each poti.

I changed all the old caps and some of the restistors, that showed too differend value from what the should be. I again used carbon comp. resistors to keep some of the old still sound.
Even this pedal is already true bypass, I installed a 3pdt-footswitch adding a status led.
Little bid tricky, because the original footswitch has a longer shaft, so you have do install a (second) spacer rubber or something equal below the moving pedal part of the enclosure.

For more sarisfying "yoy yoy", I first changed the L2 inductor to a old Dunlop standard 500mH inductor - no real improvement.
Then I reinstalled the original L1 and put the Dunlop 500mH coil on position L1. And that was the tweak to make the pedal sound !!!

I also reversed the left & right joints ( CW & CCW) of the volume poti, so the sound is on maximum volume, when switched off.

At the tdpri-forum I found a question, what to do, if the double poti is broken or scratchy.
As far as I can see, one can also install every single wahwah poti, only the volume funktion isn't given then anymore.
Which is not the worst, because as every Wah/Volume pedal I know, also this Schaller Yoy Yoy sucks tone and volume.
An alternaitive to keep the volume control might be to use the 3pdt-footswitch (or, if you want also a led, a 4pdt-footswitch) and install a "groundlift" to the pcb.
That's the way it could be done with Dunlop-style wahwah and as I saw from Dino's picture here at the start of the thread, the first series with the metal enclosure aso uses a single potentiometer.
But this is more a guess and not a verified idea.

Thanks for watching and all the best to all you DIYers,

Buud

I updated the schematic long ago, but I can't remember if I ever published it here. In any case, here is the proper one, as per my own personal unit.



BC239 transistors were also used in these, as well as some others that I can't remember off the top of my head right now.