Bench tool
Voltage Divider & Dropping Resistor Calculator
Size the dropping resistors that step B+ down for preamp nodes, chain a full multi-stage decoupling network, or work out a bled voltage divider.
Single Dropping Resistor
One resistor between a supply node and a target node, carrying the current that node draws. Covers the everyday case — dropping B+ down to a single preamp plate or screen voltage.
Nearest E24 standard value: 100 kΩ — with that value the actual output sits at 180.0 V.
Rule of thumb: rate the resistor at roughly 2× the calculated dissipation. Inside a hot chassis with limited airflow, err toward 3× on anything running warm to the touch.
Multi-Stage B+ Network
Model a real decoupling chain — B+ stepping down through successive R-C nodes toward the front-end gain stage. Each resistor carries its own stage current plus everything further downstream.
| Node | Target V | Current (mA) |
|---|
Order stages from nearest B+ (highest remaining voltage) to farthest (the first gain stage, most filtered). Each resistor's current is the sum of its own stage plus every stage after it — that's why the resistor closest to B+ usually runs hottest.
Loaded Voltage Divider
Two resistors set a voltage between a supply and ground, with a bleeder current flowing continuously to keep the node stiff against the load it feeds.
The bleeder current is a design choice, not a measurement — pick it too low and the node sags badly whenever the load current shifts; pick it too high and R1/R2 waste power for no benefit. A common starting point is 5–10× the expected load current.