Vox V847 Wah Mod.Does make sense?

[soupbone]

I've got a Vox V847 (u.s. made) that i've been doing some mods to.I changed the "vocal re." to 68k.(I like 56k too) Changed the "midrange re. to 2.2k.Changed the "input" re. from 68k to 47k.I was gonna swap out the 510ohm re. to 470ohm,and I accidentally put in the 1.5k re. in it's place,and I really like the result.I desoldered it,and put in some sockets.I tried 510ohm,470ohm,430ohm,390ohm,and 360ohm.I noticed when I tried these,it boosted the gain too much,and had this nasty tone when I rocked the pedal slow from heal to toe.When I put the 1.5K back in,all the unwanted gain was gone.Why would this work?One thing I will add is the volume is less.Not sure how to get the volume level back now.

[soupbone]

I've got a Vox V847 (u.s. made) that i've been doing some mods to.I changed the "vocal re." to 68k.(I like 56k too) Changed the "midrange re. to 2.2k.Changed the "input" re. from 68k to 47k.I was gonna swap out the 510ohm re. to 470ohm,and I accidentally put in the 1.5k re. in it's place,and I really like the result.I desoldered it,and put in some sockets.I tried 510ohm,470ohm,430ohm,390ohm,and 360ohm.I noticed when I tried these,it boosted the gain too much,and had this nasty tone when I rocked the pedal slow from heal to toe.When I put the 1.5K back in,all the unwanted gain was gone.Why would this work?One thing I will add is the volume is less.Not sure how to get the volume level back now.

Is the 68k resistor the one that controls the output volume of the wah?Maybe use a 100k trimpot?

[Luke51411]

A schematic would help but from my memory of wah modding the 68k you put in probably controls the "Q" the 470 in conjunction with another resistor controls the gain. If you have too much gain, certain frequencies will cause the transistor to clip in a nasty way. This article tells you what every component does. http://www.geofex.com/article_folders/wahpedl/wahped.htm

[joegagan]

yes, you effectively rebiased Q1 to a low gain with that 1.5k to ground.
there is an interactive dance between the input R and this Q1 E to ground R. if you use a 500 ohm trim at Q1 and 100k trim at input R, you will be able to dial in the exact amount of growl and or clean you like. the 500 ohm will effect low end more, the 100k will increase or decrease overall volume more.

i also prefer a gain of 120 to 160 for Q1. makes for a less hissy situation along with nice musical tones.

[soupbone]

yes, you effectively rebiased Q1 to a low gain with that 1.5k to ground.
there is an interactive dance between the input R and this Q1 E to ground R. if you use a 500 ohm trim at Q1 and 100k trim at input R, you will be able to dial in the exact amount of growl and or clean you like. the 500 ohm will effect low end more, the 100k will increase or decrease overall volume more.

i also prefer a gain of 120 to 160 for Q1. makes for a less hissy situation along with nice musical tones.

Thanks for the explanation Joe!I had no idea what I did!lol Some nice info there!  

[soupbone]

A schematic would help but from my memory of wah modding the 68k you put in probably controls the "Q" the 470 in conjunction with another resistor controls the gain. If you have too much gain, certain frequencies will cause the transistor to clip in a nasty way. This article tells you what every component does. http://www.geofex.com/article_folders/wahpedl/wahped.htm

Thanks Luke!