How to tame a high voltage output

[Grainger49]

Take a look here:

http://www.siteswithstyle.com/VoltSecond/12_posistion_shunt/12_Position_Pure_Shunt.html

There is a lot of information on the page but what you want is Figure 2.2.1 Trick 1.

 

[PassionForSound]

Thanks for the great link Grainger.

Can someone answer the question of how the series resistor value is calculated? Is the series resistor just there to keep the load on the source the same?

 

[Paul Birkeland]

The series resistor both reduces the voltage and helps set the impedance.

 

[chard]

I just googled L-pad calculator and found a nice fill in the blank calculator that came to this solution. Series resister 75k, shunt resister 33k in parrallel with 100k pot. This circuit will attenuate 75% of your input signal.
  Because the 33k resister is in parrallel with 100k pot their combined resistance is about 25k. This circuit is a voltage divider network with a series resister of 75k, which is labeled R1 and a shunt resistance of 25k, which is labeled R2 and an overall imput impedance of 100k or R1+R2 . The voltage divider rule is: voltage out= voltage in x R2/R1+R2.  In your case 6.8volts x 25k/100k=1.7v
  To use the calculator you will have to know the level of db reduction you want. In your case you want a 12 db reduction which is a  signal reduction of 75%.

 

[PassionForSound]

I just googled L-pad calculator and found a nice fill in the blank calculator that came to this solution. Series resister 75k, shunt resister 33k in parrallel with 100k pot. This circuit will attenuate 75% of your input signal.
  Because the 33k resister is in parrallel with 100k pot their combined resistance is about 25k. This circuit is a voltage divider network with a series resister of 75k, which is labeled R1 and a shunt resistance of 25k, which is labeled R2 and an overall imput impedance of 100k or R1+R2 . The voltage divider rule is: voltage out= voltage in x R2/R1+R2.  In your case 6.8volts x 25k/100k=1.7v
  To use the calculator you will have to know the level of db reduction you want. In your case you want a 12 db reduction which is a  signal reduction of 75%.

I think that was the piece of the puzzle I was trying to grasp - thank you. I understood the general concept and also found various calculators, but I was trying to understand the exact maths that went into the value for the series resistor. I was under the impression that it was the difference between the starting input impedance (e.g. 100K) and the resultant impedance of the input impedance + parallel resistor. It seems it's slightly more complex so I'll just rest with the formulas provided.

Thanks everyone for your help!

 

[Grainger49]

One thing that makes this odd is that we don't hear voltage reduction in a linear way.  Cutting it in half then cutting to 1/4 doesn't sound the same.  Our volume pots are logarithmic not linear.