470K vs 100K wah pot

[rymac]

I'm looking at replacing my cry baby wah pot. What's the difference between 100K and 470K wah pot?

[Chuck H]

470k = more wah
100k = less wah

With the bigger pot rocking the treadle goes from thin whistling uncontrollable treble to "Oh my god, who sucked the life out of my tone?"

The stock pot will trim both ends and give a more midrangy character to the pedal.

I actually place a rubber bumper on the tail of my wah to keep me from rocking it too far down. Then I adjust the pot gear a few teeth back to keep from going too far up, narrowing the range even more.

So this is just my opinion. You never know if it's for you until you try it.

Chuck

[rymac]

Thanks for the advice. I think I'll go with 100K.
Rymac

[R.G.]

It's interesting to note that the wah pot is after all just a voltage divider. It sets the amount of collector output from the first transistor that gets into the base of the second transistor from 0% (bass) to 100% (treble).

If the loading of the wah pot on the first transistor's collector didn't have an effect on the overall gain of the transistor, the specific value of the pot would have no effect on the wah range at all. This can be demonstrated by placing an emitter follower on the collector of Q1 to buffer Q1 from the wah pot.

The reduced loading of the 470K pot accounts for the changed range; but this is negated if what follows the wah is too low-impedance, and itself loads the collector of Q1.

[vincediamond]

RG makes it sound like its a DC voltage divider when really its a AC frequency voltage divider

Changing from 100K to 470K will change the Loading value for the next stage that will change the AC Gain

But also the RC time constant changes , the way the 0.22uf is connect to the 100k wah pot is a passive high pass filter

So its really a "passive RC high pass filter" stuck inbetween Q1 and Q2

CRC network:
its a RC high pass filter from the output of Q1 to the wiper of the wah pot and a RC low pass filter from the wiper of the wah pot to the input of Q2

Depending on how you look at it

[Stamp]

It's big pleasure to be here(I'm from Ukraine). I've just ordered 470k wah pot, but before that already knew about large output impedance of first VAS. 470k can cause much thermal noice then 100k.

As R.G. have mentioned, buffer after voltage amplyfying stage can increase wah range. I've simulated it in Microcap and noticed that extra buffer wah range begins not from 390Hz but 370Hz!

R.G., Big honor to You and your articles! There are some moment there that are still under black carpet. can we discuss them in skype?