Transimpedance Phonostages

Zero-ohm input phonostages operate an MC cartridge in current mode. In this case, damping is not external, but internal. Bandwidth (-6dB) occurs when the coil's inductive impedance matches it's resistance. At that point, current is halved. This happens at R = 2*pi*f*L. Here is a plot showing frequency response for a cartridge coil of 10 ohms:

To calculate bandwidth of your cartridge in current mode, use this calculator: