freestompboxes.org

borrowed it from a friend so I could post some gut shots

first time to see a wah not using a pot or LDR for the wah sweep

uses a magnet which raises/lowers from the pcb (on the spot atop U1)

on the left side of the range knob, there is a yellow square with an inverted horseshoe inside

written below is "MAG-POT" , it just dawned on me that it pertains to the sweep pot and not the range knob

Thanks for the pics. Looks like a well built piece of equipment. Too bad its all surface mount. I think I may have to try my hand at surface mount stuff at some point.

Hi euronymous,

I'm intrigued to see how the magnet are positioned respect the pcb.

Can you post some pics of that particular magnet and how is phisically mounted ?

BTW, is that magnet a strong one or weak ?

Cheers,
Jose

Very interesting approach. Does it sound good, with a nice even pedal sweep?

I, too, own a wah like this one (not exactly this, but the APW-7 which has a "whish" knob and a normal/bass switch as well). It is a great wah, its sweep is even and it has lots of opportunities to tinker with.
When you turn the whish knob all the way up with the bass switch on (on mine) it goes into a nice self-oscillation.

i was not able to fully test it, but AFAIK it has a nice sweep.

i think that it has a slower response compared to crybabies

here is a a quick drawing of the positioning of the magnet, i think that it has a normal strength of magnetism (maybe similar that of those found on you stick on your fridge )



place where the magnet raises and lowers

Does it suck tone?

Thanks

I think I see an LDR/LED package in there, as well as a toroid.

Is the magnet moving the board away from another plane of some sort? I'm thinking the distance between the "heating coil" traces (or whatever those look like to you at 3am drunk) and some other plane could be forming a variable capacitor, perhaps maybe in some way of sorts? Would that be enough to vary the center frequency?

My guess is that U1 is a linear Hall Effect device.

The area highlighted in red is just there to try and fool us IMO. It is just a fancy shaped trace, the outside square is continuous.

deltafred wrote:My guess is that U1 is a linear Hall Effect device.

Yes, it's a Ratiometric Hall Effect Sensor, like A1302, SS496 etc.

dimych wrote:

deltafred wrote:My guess is that U1 is a linear Hall Effect device.

Yes, it's a Ratiometric Hall Effect Sensor, like A1302, SS496 etc.

Well, homework time.

Sorry to bring this old thread back to life but I have the oportunity to buy one of these used & cheap to change to a volume pedal. The problem is that all that I wanted to keep was the case/shell, rocker mechanism and... pot! That's the problem this baby has a very strange pot and I can't find any schematic or detailed information. It seems that the Hall effect driver produces a voltage depending on the position of the magnet on the "foot plate" that actually drives a LED/LDR pair that is the "real" pot of this circuit. I'm I correct? Does anybody knows the voltage limits or better the reference of the parts (Hall effect driver and LED) used?
I already have a LM13700 Dual OTA (Operational Transconductance Amplifier) to build a nice active volume pedal. I wonder if with this Artec arrangement (Hall+LED/LDR) still makes sense to make that LM13700 project or if I sould change it to a simpler circuit (gain adjustable OPAMP circuit)...

I already got it but few time to deal with it. When I have something I'll post it here.