Weekend Project

A Minimal Art Direct-Conversion Receiver for Low-Impedance Headphones

Here's a version of the Minimal Art direct-conversion receiver for use with low-impedance headphones. To prevent hum, I recommend keeping the ground connections as close together as possible. Compared with the high-impedance headphone version, one more AF amplifier stage is necessary, because the final AF stage is used as an "impedance transformer."

There is also a version with a passive AF filter for CW reception. Vintage high-impedance headphones have a frequency-response peak at about 1 kHz, which acts as a simple CW filter. Modern low-impedance headphones are broadband, so an additional CW filter improves selectivity. I used ordinary small 4.7 mH inductors from an electronic parts supplier.