Wacky Wah Wah Wiring Weirdness

[10acErnie]

I'm having a heck of a time trying to figure this one out.  I'd like to use a battery adapter with my vintage Cry Baby. When using my Boss PSA 120 power supply with my 1972 Cry Baby I get a pretty bad hum when the Wah is engaged. I attached the 9v supply directly to the battery clip. I pluggged the guitar directly into the wah & the wah directly into the amp. I don't have any other effects in the chain.

The weird thing is when I remove the 9v adapter from the battery clip and touch the positive terminal of the battery clip it sounds like I'm touching the tip of the cord going into the amp. So I guess this means 9v is getting into the tip of the guitar cable sending voltage into the input of the amp?

I thought something may be wrong with the wiring so I tried my other early 70's Cry Baby and got the same result! Then I decided to try this with my 95Q and it didn't behave the same way, it was fine. The same goes for my Bud Wah and my 535Q, they were fine also. I should add that none of my other pedals behave this way so I think the adapter is allright. (well the Green Ringer I just built is giving me a little 60hz trouble but I'm still trouble shooting).

I'm kind of new at this but looking at the schematic from Fuzz Central it looks like +9v is going into a 22k resistor then to a .22uf cap then it goes to the output. Is that why I'm getting this hum? Is there a work around or a fix or a way to filter the voltage? I really would like to use a 9v adapter.

I did a search on the forum and couldn't find an answer. I also checked Fuzz Central, GGG, and GEO and had no luck.

Thanks!!!

[jimmy]

i may be wrong, but i imagine the crybaby circuit has changed slightly to add some power supply filtering or something since the 70s. that would explain why the more modern wahs are ok.

if youre up for it, you could put an 100 ohm resistor in series with v+, then after that an 100uF cap from v+ to ground. thats a pretty standard way of cutting down noise from the power supply.

good luck

[petemoore]

Most of my circuits will pass buzz through one of the battery clip buttons.
 This tells me [for one thing] that V+ Isn'T connected to ground.
 If a circuit uses electronic switching of course Nothing gets through without power.

[Paul Marossy]

you could put an 100 ohm resistor in series with v+, then after that an 100uF cap from v+ to ground. thats a pretty standard way of cutting down noise from the power supply.

Yep, that should do it. A 220uF cap should completely whack any hum from your power supply (not that 100uF wouldn't work).

[10acErnie]

you could put an 100 ohm resistor in series with v+, then after that an 100uF cap from v+ to ground.

Thanks!
Is this correct? Should the cap be polarized?

[no one ever]

find out what zvex did with his power plates?

[David]

i may be wrong, but i imagine the crybaby circuit has changed slightly to add some power supply filtering or something since the 70s. that would explain why the more modern wahs are ok.

if youre up for it, you could put an 100 ohm resistor in series with v+, then after that an 100uF cap from v+ to ground. thats a pretty standard way of cutting down noise from the power supply.

good luck

1000uF or 2000uF will do even better.  And yes, it needs to be polarized.  Check out "The Spyder" on GEO or Scott Swartz's 4-output power supply on General Guitar Gadgets for how to orient the caps.

[10acErnie]

i may be wrong, but i imagine the crybaby circuit has changed slightly to add some power supply filtering or something since the 70s. that would explain why the more modern wahs are ok.

I tried the 100uf, 220uf a 470uf and then a 1000uf. It's better but there is still a noticeable hum.
While fishing around the net I read somewhere that old Wah's don't like power adapters so I guess Jimmy is right. Does anyone have a schematic of a newer wah or know how the newer circuit differs from the old units as far as filtering?