An impedance conversion device includes: a first input terminal to which a first analog signal output from an electric musical instrument is input; a splitter configured to split the first analog signal into a second analog signal and a third analog signal; a first output terminal from which the second analog signal is output; an impedance conversion circuit configured to convert an impedance of the third analog signal; and a second output terminal from which an analog signal obtained by converting the impedance is output. An input impedance of the impedance conversion circuit is approximately 1 G or more.

Apparatus and associated methods relate to training FIR filter coefficients by deconvolving a first input signal and a second input signal in the frequency domain, both of the signals being generated in response to an undetermined broadband excitation applied to an acoustic body instrument, until a fidelity of the second signal convolved with the trained coefficients meets predetermined fidelity criteria relative to the first signal. In an illustrative example, a musical instrument pickup signal and a microphone signal from the musical instrument may be sampled, segmented, and transformed to the frequency domain. FIR filter coefficients may be, for example, trained by block deconvolution in the frequency domain of the microphone signal and the pickup signal. In various examples, the trained FIR filter coefficients may adapt the pickup signal to mimic microphone performance, including full-body acoustic content.