Adding resistors to a volume pot

[Mgaith656]

Hello,

I have a a few questions regarding adding resistors to a volume pot:

1- Can the quality/brand of resistor change the sound (do some brands sound better than others)?
2- i have done the suggestion in FAQ#3 but i want to know the idea behind it (i get that adding resistors to to input pad the pot but why add  another pair of resistors to the ground lug necessary? Do the quality of the resistors have to be same for the ground lugs or it doesnt matter?
3- is there a fixed value when adding resistors for the ground? (Does it have to be 33k to ground when i install 75k to the input)
4- lastly is the recommendation in the FAQ#3 called “in series” or “parallel”

This is my first post here and i think that the idea of Bottlehead is very interesting as i  am learning new things everyday. Thank you

Any help would be of great value… Thanking you in advance.

 

[Paul Birkeland]

Yes, different resistors can sound different, though there isn't necessarily a strong correlation between price and sound quality. 

The idea behind FAQ #3 is to reduce the maximum level of signal that can come out of the potentiometer.  You could conceivably achieve the same results with a single resistor per channel, but there are some negative consequences to making the impedance of the level control too high, so we aim to keep it pretty close to 100K.  The 33K resistors in parallel with the pot allow the 75K resistor to be relatively low in resistance value to achieve the desired attenuation. 

FAQ #3 has resistors in parallel with the pot (33K) and in series with the pot (75K).

 

[Doc B]

Another way to look at it is as a voltage divider - two resistors in series from the voltage source to ground, with a tap being taken off the junction of the two series resistors. Many references available online -

https://learn.sparkfun.com/tutorials/voltage-dividers/all

https://www.allaboutcircuits.com/tools/voltage-divider-calculator/

Your volume control is a variable voltage divider composed of series resistors created by the pot output wiper dividing the resistive track in the pot into two variable resistors. To make it less sensitive a second, fixed voltage divider is installed ahead of the volume pot to reduce to maximum voltage that the volume pot sees from the source. This effectively makes the volume pot circuit less "hairtrigger" and reduces the maximum voltage output of the pot.

As PB says this method can preserve the impedance of the pot. If you instead use a single resistor feeding the pot to increase the voltage divider ratio of the pot (and lower the output voltage) you are keeping the circuit a single, variable voltage divider while making the "top half" of the volume pot voltage divider resistance much bigger, thus increasing the pot's impedance.

 

[Mgaith656]

Thank you for your replies. I guess one can figure out so many ways to change the sound while continuously learning.