Resistor ratios can be adjusted to fine-tune the signal strength. The difference signal is applied to U3's Y input, and the sum to the Z input. The X input is the output of the frequency doubler, U4.

For the 1% resistor, the value of N = 96, for 2% N = 48, and for 5% N = 24. This formula is true for 1% and 2% standard resistors, but the 5% resistors do not track exactly.

The fourth band indicates the tolerance. For example, if the first two bands are black and red, the corresponding value is “02.” If the third band is yellow, that represents a multiplier of 10K ohms.