Resonant Choke Filter Revisited
I just simulated a simple parallel inductor capacitor circuit. A 4H choke (common size for a guitar amp) requires a 440n cap to get a notch at exactly 120Hz. But with a 470n cap for example, the notch would be at 116Hz and so you would only get about 12dB attenuation (as opposed to more like 40dB if it really is tuned). Load has no effect on the resonance of the circuit in the simulation. I don't think it would work with SMPS because those chokes are usually pretty small. For example, a 100uH choke and 101.3n cap would resonate at 50kHz. But because the choke is so small, the notch is very narrow. I had to use 10ths of nano-farads to really get the 50kHz.