Quick FET Question

[kurtlives]

Regarding Andy's Sparkle Boost...
Well the only schem I know of is from Andy's site and he has taking the site down.

So referencing this layout. (it`s easy to look at the layout and figure out the schem)


What is the point of the 100K (R4) resistor going from just before the output to ground?

When I breadboarded it I couldn't really hear a difference with it in the circuit or out. Can anyone explain the purpose of it?


Thanks...

[Ripthorn]

Usually a high value resistor going from just before output to ground is a pull down resistor which helps eliminate the pop when switching the effect on and off using a switch.  It is not meant to alter the sound, but provide an outlet for the pop.  I think it is strange that it is 100k and not 1M if it is a pull down resistor, but then again, that may not be a problem.

[cpm]

it will be parallel to the level pot, maybe he wanted a 50kB pot, only having 100k at hand?

[kurtlives]

Those were my exact thoughts guys...

But like said 100K seems a bit small for a pull down. I do remember reading though that pull downs at the end are usually smaller in value than the input.


Maybe the resistor is to make the pots value 50K? On the original schem the volume pot was log taper. The 100K pot would make it 50K with a funny half log taper.