I'm building a Schaller "Bow Wow Yoy Yoy" Clone!

[Paul Marossy]

I designed a PCB layout last night that is based on using Fasel inductors. I'm going to etch it this weekend and populate it as much as I can. The PCB will be the same dimensions as the 80s Cry Baby wah boards (roughly 3"x2"), so all that will have to be done is to pop it into a CryBaby shell. I'll keep y'all posted on my progress.

I have a couple of questions for anyone who might know the answer:

1. Where in the world do I get a heavy duty reverse log pot from?! Would a Dunlop Hot Potz II work OK?
2. Transistors. Anyone know what transistors were used in the original (or what should be used)?

Thanks! 

EDIT: OK, according to this schematic http://www.diystompboxes.com/pedals/schall.gif , the transistors are BC239s. (I don't know if the schematic is correct, but I used one from another source that I trust)

[A.S.P.]

somebody asked a while ago here, whether there was need for those pots
(NOS 100k neglog with mounted pinion from the OEM)
there were no replies...

[Ry]

I can't answer your questions but I'm really interested in this project.  I can't wait to see and hear how it turns out!

Ry

[Paul Marossy]

Well, here's a picture of the etched PCB:



My PCB design appears to have no flaws that I am aware of. It's got quite an interesting sound. It seems to be more of a variable filter than a wah type pedal, but then again, I don't have a reverse log pot to try with the circuit. It's really hard to describe what it sounds like. For now, I used a couple of 600mH inductors that I pulled from an old Realistic graphic EQ, but I guess I'll get a couple of Fasels to put in the circuit to see how that sounds. I was also playing with the sweep cap values, and I can't really decide what sounds best - I've tried the 0.0047uF cap as specified on the schematic, a 0.01uF, 0.0022uF, 0.68uF and a 0.1uF - they all sound different and they all could be useable depending on what you wanted. I used a trio of 2N5089s with an Hfe of over 800. But I think the biggest problem I have is the pot. I've got to figure out something for that...

I'll post my PCB layout shortly for the curious. I think it will just fit in a CryBaby enclosure, but I haven't verified that yet. It's made from that crappy RS PCB kit that I refer to here: http://www.diystompboxes.com/smfforum/index.php?topic=39838.0

[Paul Marossy]

OK, here's the PCB layout. It prints out slightly smaller than actual size, but it should be close enough to use without any real problems.

[puretube]

somebody asked a while ago here, whether there was need for those pots
(NOS 100k neglog with mounted pinion from the OEM)
there were no replies...

http://www.diystompboxes.com/smfforum/index.php?topic=24043.msg155054#msg155054

[Paul Marossy]

I guess this would be one case where you would need one of those pots.

[alfafalfa]

Hi Paul,

I watched this post with interest because I had one of these pedals back in 1968 and always regretted selling it.  Could you post some clips and I'll see if I can remember the sound. I sure do recollect the joy joy sound  but unfortunately it wasn't very usable.
This was one of those wahs which could give me endless sustain on a certain frequency together with my vox ac 30..
My modern Crybaby  535 has a sweep which is much too wide.   
Recently I've made my own inductor which is quite good but not exactly it.
So what I would like to know is where can I get one of those  100 K neg log pots ?

Regards, Alf

[Paul Marossy]

Hi Alf, ok we'll do that after I redesign the PCB. It won't fit unless you lay the inductors down on their backs, but I'm not totally happy with the layout at the moment. I'm going to do a GCB-95 style PCB, I think that will work out better in this case. Stay tuned...

[Phorhas]

Hi Paul, I saw your post and opened up my wau-wau. an original schaller, and it has 3 BC239c indeed. good luck

[Paul Marossy]

Thanks for the tip on the transistors, Phorhas.

I've got a revised PCB layout here. I probably won't be able to verify that it works OK for a week or so. Anyhow, this one should just squeak by as far as the inductors fitting in a CryBaby wah shell is concerned...

[Paul Marossy]

OK, I built it per my new layout and it's fully functional as designed. It should now also just fit in the standard CryBaby wah shell - it's basically a drop-in replacement for the GCB-95 PCB. Here's a couple of pics of the new PCB:





Now, if I could only get my hands on a 100K reverse log pot... 

[puretube]

Paul: sorry, haven`t found the bag of goodies yet... (next week).
only have the one I played with last year at hand:





pot won`t come for X-mas, but for the new year...

[Paul Marossy]

Thanks puretube! I'll put it on the back burner for a couple of weeks. 

[A.S.P.]

anyone tried BC 239 B in this or similar circuits?
just found an old box with 2000 of those NOS made by Siemens.

[Paul Marossy]

Wouldn't the BC239B be lower gain than the BC239C, or is it the other way around? I can't remember...

[A.S.P.]

yes, lower...

[Jaicen_solo]

FWIW, I know of a source for reverse log pots in the Netherlands if you're struggling.
They accept credit cards and ship internationally. I'm hoping to get some for my Neovibe when I get round to it.

[Paul Marossy]

yes, lower...

They might work if they are in the higher end, speaking of Hfe. The Bs range from about 200-450 and the Cs range from about 400-800.

[puretube]

Ouff - finally found`em... (they were in a box between the "speaker department",
where I hadn`t searched before...)


you want the one with mounted cog-wheel, right?
or rather the "naked" one?
or both? 

the original NOS pre-wired for Schaller Volume pedals 100k neg log pot...

will go to the post-office on monday.