Taking a pedal apart.

[LightSoundGeometry]

i have a pedal which has what looks a 120k resistor on lug 1 to ground on the drive pot of a boost pedal. What actual functionality does this do to the drive of a boost or dirt pedal for example?

I been running just a regular ground wire to the output jack or leaving the lug open in a build similar to this.

[Kipper4]

I'm guessing here but that 120k is stopping the resistance of the pot from going to gnd 0v therefore there will always be some drive/gain.
Like I say I'm just guessing without seeing a schematic of what your talking about.

I used this trick in my B52 high gain drive.
Maybe a search will turn that up.
Rich

[LightSoundGeometry]

I am taking apart a brilliance boost to look at a few things I had some intrigue about - I am actually surprised the soldering looks like mine under a magnifying glass. I have come along way with my soldering techniques. not sure I can post the guts online or not lol


its a five color band Resistor ..hopefully I am reading the bands right ..soon as I get home I can put a DMM across the components and take better measurements.

[Kipper4]

Look here for example the 51k resistor in the negative feedback loop of the clipping amp means that there's always some resistance in the feedback loop to create some gain even when the drive pot is fully counter clockwise.
I hope this helps
Rich

[GibsonGM]

Yes, a limiting resistor...limits how much you can turn down something...provides a minimum resistance.
Some circuits can go to "zero"...there would be no volume if you turned the pot all the way to zero R.   

So some is provided, to prevent totally silencing the circuit.

[Kipper4]

You could do the same by adding a eg 10k fixed resistor between the 100k gain pot and ground in rogs Brittania
See here

http://www.runoffgroove.com/britannia.html

[Kipper4]

Brilliant thanks Mike for the confirmation and terminology.
Just when I think I'm getting the hang of this stuff I realise I can still stuff up a simple single jellybean booster.
Carry on.

[LightSoundGeometry]

nice. I want to run some simulations when I get more time. I am looking at the way he wires up his bypass and LED switching..I am trying to eliminate as mush mechanical popping and similar noise in these high gain pedals as I can ...got me a few feet of that shielded/grounded wire to mess around with.

[GibsonGM]

Other than the usual pop stops, LSG - I wouldn't personally try to spend TOO much time making them ultra quiet. It's the nature of the beast...ANY noise will be super-amplified in a high gain circuit, by definition.  So, even a teeny tiny (leakage) DC pop, really nothing...will get amplified and make the lovely *POP* for us.   It is almost impossible to eliminate.

Just the standard practices you're learning, and talking about, should be fine!  Good wire routing, shielding, star grounding, and pulldown resistors will make 'em about as quiet as we can reasonably get 'em...

Rich - you didn't stuff up anything, you nailed it!