Snarling Dogs Bawl Buster Schematic and Inductor Info Here>

[cjenrick]

been diggin into this pedal

here is what i came up with. note that this pedal has a 33K resistor stuck in the wrong place factory screwup there are notes on this schematic about this.

enjoy!

[cjenrick]

inductor info>

[cjenrick]

did some tests on the original inductor

we used a signal generator and current meter to do these tests.

here is a graph showing how the inductor responds to frequency>

[cjenrick]

here is a graph showing how the inductor responds to changes in voltage level>

[cjenrick]

this core would work if you wanted to wind your own inductors.

or have somebody at a shop wind them which would be a lot easier

[jatalahd]

Neatly documented info, I like it! With a 1.4 H coil, the sweep is assumed to affect more on the lower frequencies than in the "traditional" wah. It also seems that extensive care has been taken to shield the inductor from external noise.

[willienillie]

Thanks to cjenrick for posting this schematic.  A friend brought me a Snarling Dogs Black Bawl wah today to work on.  It's not really broken but sounds pretty bad.  Very dark.  So far it seems to be the same as this Bawl Buster but without the sweep cap switch.  It has the incorrectly connected 33K.  It has a knob on the outside labeled Volume but I think it's the same as the Boost in the schematic above.  It doesn't make the pedal louder, just bassier and more distorted.  Kinda silly, the 100K resistor at the output could have been a real volume pot.  I might replace that with a sweep cap rotary switch instead.  The jacks are some of the lowest quality I've seen, like the plastic Danelectro pedals, but being board-mounted limits upgrade options.

I'll try a smaller sweep cap (I think it might be .025µF as-is), and fixing the 33K for starters.  If it still sucks I might end up gutting it and building a traditional wah circuit in the shell.  We'll see.

[willienillie]

I still don't have a question here, just want to flesh this topic out a little for anyone who has to deal with one of these wahs in the future.  Before I found this thread, I came across this hand-drawn schematic for the "Wonder Wah" on another site:



Though I haven't checked everything, it seems to match the Black Bawl except it doesn't have the Volume/Boost control.  It even shows the 33K (R6) in the wrong place.  As far as I can tell, the one I'm working on is one of the late models, it doesn't have the "Charlie Stringer" name on it.  I don't know when the R6 error came along, but I've seen gut shots of earlier versions with wired jacks and a different PCB.

But anyway, I moved the 33K to parallel the inductor, I took C9 and C10 out (22n and 3n3 in parallel), and dropped a 10n in for the sweep cap.  It sounds pretty good now.  Like a regular wah pedal.  I'm not crazy about the pot's sweep, most of the action is bunched toward the toe-down end.  I'll have to see if I can shift the pot physically, it's kinda hard to describe how it's mounted, but not like a Crybaby.

I haven't messed with the Volume control since I made these changes, will play with it more tomorrow.

[Side note, I think D1 might be drawn incorrectly in both schematics.  Not sure yet.  I didn't look at that portion when I had the board flipped over, but powered up with a battery I measure 0.0V across D1, and I think it's at least backwards in cjenrick's schematic.  Eh, I'll look at that again after some sleep.]

[duck_arse]

the K30A should be shown as a jfet on both circuits. there is quite a few inconsistencies around the battery section in the "AR" drawn - check those grounds. what type inductor in yours, wn?

[willienillie]

the K30A should be shown as a jfet on both circuits

Yeah I saw that.  It is a K30A.

what type inductor in yours

It's a big metal can.  The only info I've gathered about it is in the posts above.  My meter doesn't measure inductance.  DC resistance is about 14 ohms (in circuit), which seems a little low, but I guess it comes down to wire guage.

[willienillie]

I'm done messing with this thing.  After the resistor fix and sweep cap swap, for whatever reason, the Volume control seems pretty useful now, though calling it Boost would have been a little more appropriate.  It does raise the volume some, and thicken the tone slightly, not just get distorted and weird like before.

I was only able to rotate the pot a few degrees without hitting the physical limit.  That helped, but the sweep is still not the best.  The gear teeth aren't the same as a Dunlop pot, so there aren't any easy drop-in replacements.  But overall this thing sounds night and day better than when it was brought to me, the owner will be happy enough.

FWIW, it works perfectly in front of a Fuzz Face, at any setting of the Volume control.  That added JFET stage does the trick.  I don't just mean it doesn't howl, it has a normal wah range too.  I might have to rip that off for a build someday.

[duck_arse]

what type inductor in yours

It's a big metal can.  The only info I've gathered about it is in the posts above.  My meter doesn't measure inductance.  DC resistance is about 14 ohms (in circuit), which seems a little low, but I guess it comes down to wire guage.

I was hoping you'd say toroidal.

[ future edit :] tattoo design.

[willienillie]

I was hoping you'd say toroidal.

Pics above suggest 2 toroidals in series, I didn't try to open the can though.

[anotherjim]

I can't get my head around the humbucking.
Is it two identical coils stacked back to back (or face to face) or is one CW and t'other one CCW?

And Ducks, is that a plague-doctor avatar at the moment?