Calculate voltage loss and treble loading when connecting a guitar pickup to an amplifier. Enter pickup DC resistance and amp input impedance.
Enter the pickup's DC resistance in ohms and the amplifier (or pedal) input impedance in ohms. The loading ratio is simply input impedance divided by pickup resistance — the higher it is, the less the amp loads down the pickup. A classic 8 kΩ single-coil into a 1 MΩ amp input gives a ratio of 125:1, which is effectively no loading at all.
Signal loss is the voltage-divider attenuation expressed in decibels: with 8 kΩ into 1 MΩ the loss is only 0.07 dB, inaudible in practice. A hotter 15 kΩ humbucker into the same 1 MΩ input still loses just 0.13 dB. Treble loading is reported as an approximate percentage of pickup resistance relative to the load; both example pairs stay near or below 1.5%.
Problems appear when the load drops. Feeding that 12 kΩ pickup into a 100 kΩ input collapses the ratio to about 8.3:1 and pushes signal loss near 0.98 dB with roughly 12% treble loading — audibly darker and quieter. The tool flags 10:1 or higher as an excellent match, 4:1–10:1 as acceptable with slight treble loss, and anything lower as a mismatch that benefits from a buffer or preamp.
A passive magnetic pickup is a high-impedance source. When the load it sees (the amp or pedal input) is not much larger than its own DC resistance, the two form a voltage divider that drops the signal level and rolls off the treble. Keeping the load far higher than the pickup preserves both volume and high-end sparkle.
A ratio of 10:1 or higher (load to pickup) ensures minimal loading. Most amps present a 1 MΩ input, which is ideal for 8–15 kΩ pickups: an 8 kΩ single-coil sees a 125:1 ratio and a 15 kΩ humbucker about 67:1 — both effectively unloaded.
Almost none. An 8 kΩ pickup into 1 MΩ loses about 0.07 dB, and even a hot 15 kΩ humbucker loses only around 0.13 dB — far below the threshold of audibility. The loss is the voltage-divider attenuation, −20·log10(load ÷ (load + pickup)), expressed in decibels.
When the load drops toward the pickup's own resistance. Feeding a 12 kΩ pickup into a 100 kΩ input collapses the ratio to about 8.3:1, pushing signal loss near 0.98 dB and treble loading around 12% — audibly darker and a touch quieter. The fix is a buffer or preamp that restores a high-impedance load; the tool flags ratios under 4:1 as genuine mismatches.