Anderton descratcher with NSL-32 - how do adjust sweep

[GeorgeSunset]

Hey all

didn't find anything with the search - so i will try my luck.

have a BYOC Wah - witch got a red fasel extra + a couple of extra sweep caps.

tried to build a Anderton descratcher witch i found on R.G. webpage
http://www.geofex.com/article_folders/wahpedl/wahped.htm

Tried it out and found out that this circuit makes the taper of the tone-sweep a bit more narrow - witch i don't like at all.
For me the sweep from bass to treble is allready to fast (standart with the pot) and the circuit makes it even more narrow

so, can I adjust the sweep from bass to treble by making adjustments to the anderton circuit?


Thanks for the help!

[R.G.]

Tried it out and found out that this circuit makes the taper of the tone-sweep a bit more narrow - witch i don't like at all.
For me the sweep from bass to treble is allready to fast (standart with the pot) and the circuit makes it even more narrow

so, can I adjust the sweep from bass to treble by making adjustments to the anderton circuit?

You can, but it's tricky.

I'm translating your post. Tell me if I translated wrong:

For me the sweep from bass to treble is allready to fast (standart with the pot)

means "There is a range of pot settings I prefer the sounds of, and the standard pot goes through that range in too small an amount of its rocking/range. I'd prefer that the 'sweet spot' range be spread out over the whole rocker range."

The stock wah circuit changes the effective gain of the first transistor through the path of wah pot->second transistor-> sweep cap -> inductor -> first transistor again. You only like a certain amount of that range. You want the full range of the pot/rocker movement to match the range of sound you like. You can do this by making the pot's resistance be a smaller percentage of the total possible gain change. You put one resistor "above" the pot and one "below" it to ground. By adjusting the values of these resistors, you can make the pot's change in total setting be a smaller fraction of the total available gain change, and also move the pot's fraction of the gain range up and down. In the stock circuit, the top and bottom resistors are both zero. If you have a 100K pot and put a 100K above and a 100K below, you effectively decrease the range of the pot to 1/3 of the whole range. And now the whole rocker movement changes the gain loop over only 1/3 of its range. In this setup, it's the middle third. By making the top resistor zero and the bottom one 200K, the pot range is still 1/3, but it's now the top. Make the top resistor 200K and the bottom one zero and now the pot range is still 1/3, but it's the bottom third.

With that under your belt, the Anderton descratcher changes the wah pot into a current control for an LED/LDR pair. The LDR does much the same as your pot did in the stock circuit, but it does it by interacting with another resistor to make a signal voltage divider. You have to adjust two things to make this setup change scale/range and position in frequency. You have to change the actual rocker pot's active range with upper/lower resistors to match the current range of the LED you need (once you find it! it varies from LED/LDR to LED/LDR) and then you have to do a similar adjustment to the LDR. 

[GeorgeSunset]

Jup - you got it!

hm... when you say "above" and "below" the pot, do you mean in front and after? (if lug 1 - input, lug 2 - output, lug 3 - ground to the pot => a resistor from lug 1 to ground and from lug 2 to ground)


i think i understand what you are saying - not so much WHY this is working, but what i have to do.
sounds like a lot of work and tweaking to get all resistors to match hm. think trimpots on a little board on the side is the ticket to find the correct values and then hardwire it with normal resistors... hm...

must say - this wah project keeps me occupied


Thank you very much for the help - your answers here on the forum have helped me a lot of times!!!





EDIT:
Hm... i think i misunderstood you! You are looking at a schematic of the circuit - so you will put a 100 kohm resistor between the pot and the output og the circuit and a 100 kohm resistor between the pot and the ground (and nothing between the pot and the sweep-cap)