Bench tool

Choke/Inductor Filter Calculator

Estimate ripple reduction and DC voltage drop through a choke filter stage, and check whether your choke's inductance is enough for true choke-input operation.

DC voltage into the choke

DC load current

Choke inductance

Choke DC resistance (DCR)

Filter cap after the choke

µF

Incoming ripple (before choke, optional)

Vpp

Mains frequency & rectification

Ripple attenuation

-35.2 dB

ratio: 0.0173 (output is 1.7% of input ripple)

Reactance XL3.77 kΩ

Reactance Xc66.3 Ω

DC voltage drop (I×DCR)10.0 V

Output ripple estimate—

✓

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Ripple attenuation is modeled as the simple L-C divider Xc / (Xc + XL) at the ripple frequency — accurate when the choke's reactance dominates the load impedance, which holds for most guitar-amp power supplies. The DC drop is separate from this and comes purely from the choke's winding resistance (DCR); the inductance itself doesn't drop DC voltage, only AC ripple.

Critical inductance is the widely-used rule-of-thumb minimum (R_load / 1000 at 60 Hz, R_load / 900 at 50 Hz, where R_load = Vdc/Idc) needed to keep a choke-input filter in continuous conduction. Below this, the filter behaves more like a capacitor-input stage — B+ rises unpredictably toward peak voltage and ripple gets worse than this calculator assumes. This tool doesn't change its ripple math below critical inductance — treat the ripple number as unreliable in that case.