Best way to imitate my guitar volume on half? Resistor on pedal input?

[chumbox]

Hey

Find with a couple of overdrives I much prefer them with my guitar rolled back 50% and do a bit of a volume dance between some pedals.  Would placing a resistor between the input and the input cap eg 100k (guitar vol pots are 250k) of these pedals be a good way to achieve this same outcome all the time (without needing to adjust my guitar volume) or is it going to create some sort of high/low pass filter with the cap?  I've seen some pedals use this methodology (Em-Drive, a few DeviEvers etc) with a pot on the input to act as the gain control so I figure a fixed resistor should be ok.

Thanks
DO

[Unlikekurt]

use a treble bleed circuit and use the pot to set the volume how you like it.  the benefit is that you won't get the loss of treble that simply putting a resistor or pot in-line would create.
search for seymour duncan treble bleed circuit.

[chumbox]

Thanks so much Unlikekurt.  Googled this and it looks the goods.

[Pojo]

Back to the question of how to simulate your guitar volume at half, you would need to implement a voltage divider with 2 resistors. Also chances are your pot is log taper and the pot at 50% does not equal 250k/2 which you were looking to approximate with the 100k resistor. So your best bet is to set your volume where you like it and measure the resistance between the center lug and the lug connected to your pickup selector. That will determine the the value of the first resistor (R1 in the pic below), the second resistor (R2 in the pic below) should be as close to 250k as you can find....perhaps 220k or 270k.

[chumbox]

Thanks Pojo.  So assuming I put the voltage divider at the input what happens to the pull down resistor (1M) that would immediately follow this?  Does it negate the need for for one or does it make the whole equation a little more complex?

[Pojo]

R2 could replace the 1M as the pull-down resistor...as long as leakages from the input cap have a path to ground while the circuit is bypassed, that role is covered.

[chumbox]

Brilliant.  Thanks so much Poko and Unlikekurt.

[ashcat_lt]

Back to the question of how to simulate your guitar volume at half, you would need to implement a voltage divider with 2 resistors. Also chances are your pot is log taper and the pot at 50% does not equal 250k/2 which you were looking to approximate with the 100k resistor. So your best bet is to set your volume where you like it and measure the resistance between the center lug and the lug connected to your pickup selector. That will determine the the value of the first resistor (R1 in the pic below), the second resistor (R2 in the pic below) should be as close to 250k as you can find....perhaps 220k or 270k.

Shouldn't R2 be 250K - R1?  It's the other half of the pot, from wiper to the the jack sleeve which some folks call ground.


On another note, it seems to me like if your guitar volume doesn't already have treble bleed on it, then at least part of what you're digging is the loss of treble as you roll down the V pot.  The voltage divider at the pedal end of the cable capacitance will not roll off treble the same way.  It will, however, sit in parallel with the input impedance and the V pot and mess with the treble in a bit different way.  Might work out close enough, but won't be quite the same.

If you do have treble bleed in the guitar, then it might actually be the loss of bass in the signal that helps it sound cool.  You'd still have the loading effect from basically having two 250K V pots in parallel, but you wouldn't get that HPF thing that the treble bleed cap creates.

Either way, it's going to be different from what you get when you turn down the V in the guitar.

[Solidhex]

Instead of doing all the measuring you could just build a passive volume control in a pedal with a foot switch. Use a 500K. Input lug 3, output lug 2, ground lug one like a regular voltage divider. Then you could use it with any pedal you want. Set it where it sounds best instead of committing to a particular resistor combo. If you're really worried about the parallel resistance with your guitar pickup you could just wire it like a rheostat (don't ground lug 1) and see if it still does the job enough for you.

[chumbox]

That's a good point Solidhex.  A very good point.