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. Try to keep the ground connections together as close as possible. I recommend this to prevent humming. One more AF amplifier stage is necessary compared to the high impedance headphone version because the final AF stage is used as an "impedance transformer".

There's one more version with a passive AF filter for CW reception. Vintage high impedance headphones offer a frequency response peak at about 1 kHz which is a simple CW filter. Modern low impedance headphone are broadband. Therefore an additional CW filter offers more selectivity. I used no special small 4.7mH inductors from an electronic parts supplier.


Version without AF filter



Version with passive AF filter