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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: voltage divider question posted by MylesJ on November 18, 2004 at 22:09:57:
Starting with the innermost pair (or multiple) of resistors in the network, compute the equivalent single resistance of the combination thusly:-for series resistors, add the resistances;
-for parallel resistors, add the reciprocals and invert this sum.
Continue to do this with the computed equivalents and the remaining resistors until you are done.
The challenge for newbies is to identify the innermost set of resistors, that are either all in series or all in parallel, to start this process. Draw the schematic and stare at it until it is clear.
Your example is slightly more complicated, as the equivalent resistance of the amp input in parallel with the pot depends on the pot setting. The lowest value it can have is 50K (the parallel combination of the 100K pot and the 100K amp input) when the pot wiper is set for maximum output. The highest value it can have is 100K, when the wiper is set to minimum output.
For the case of maximum output, the parallel combination of the pot with amp, and the 8K shunt resistor, is 6.9K. To get this, divide 1 by 8K and add it to 1 divided by 50K, then divide the sum back into 1.
The series combination of 15K and 6.9K is 21.9K. This is the lowest resistance your preamp will see. You should attempt to compute the equivalent resistance with the pot set to zero to see if you follow the method.
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Follow Ups
- The combination formulas. - Al Sekela 10:16:51 11/19/04 (1)
- Re: The combination formulas. - MylesJ 15:12:17 11/19/04 (0)
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