Information wanted

[t1mman]

Hey there!

2 questions:
I recently recover this thing I had in my teens years, used to not work properly and I didn't realy know, back then, how to fix it.

Anyway, now I got it back, repair what was wrong with it and it's back and alive!

I was woundering if anyone had any information on this baby:



I was able to retreive *some informations with the EX-600:
Aparantly made by Frontline or sub division

http://www.effectsdatabase.com/model/frontline/wahwah

but I don't have any more info on this, anyone care to share his knowledge
Does it compare to good ol' crybaby or vox?

Also, from what I can understand, it is "inductorless", so, what can be acheive or tuned on them?

And, last, a question, I find that the sweeping range is pretty "short".  Meaning it goes from high to low in realy not much movement, not enough for my tase.  Is there anyway to change that? 

I currently have a 100kb pot in it, would changing the pot help me with the sweeping range?

[Mark Hammer]

The place to start is obviously here: http://geofex.com/Article_Folders/wahpedl/wahped.htm

From the picture, there would appear to be only one transistor in there.  The only thing I can think of that would come close to that general design would be the Bespeco Weeper.  I can't give you the link, due to technical impediments, but if you do a Google image search for "Bespeco Weeper" the first hit will show you the one-transistor circuit.

You would need to reverse engineer the board from the copper side to determine which components on your unit correspond to which ones in the generic "twin-T" circuit.  Once you have that figured out, suitable recommendations can be made for things like extending or shifting the sweep range.

[t1mman]

ACtually, it is identical to this "familly"

http://www.effectsdatabase.com/model/rms/95w/metal

For the sweep range, would changing the pot help in any way?

Currently, it has a 100kb pot, from what I understand, it is "Linear".  WOuld installing an audio pot instead help?  Can it be that the pot in itself is "tired" and concentrate in one end?

[Mark Hammer]

It is often the case that the taper of any given foot-controlled pot does not perfectly correspond to that range of foot movement that provides the user comfort and accuracy when making small movements to produce specific sonic changes.

In that respect, adjusting the taper via parallel resistors is an entirely reasonable thing to do.  Given that the tuning of the filter depends on the resistance to ground provided by the pot and any added series resistance, the total value of the pot has bearing on the range of sweep.

How "tired" the pot is will play a role in how scratchy the wah sounds, but not the range of sweep.

[t1mman]

I'll check tonight, but from what I recall, I ear a difference in about half of the travel.  From toe resting to about half, then I can't ear any difference from half to heel resting.

Would it affect if I'd change the pot for a A100K instead of a 100Kb?