Earbud Adapter assembled, tested, less battery – $35
Earbud Adapter kit with all parts, less battery – $25
Earbud Adapter bare PCB and transformer supplied – $10
The #1 hardest and usually the most costly item to obtain in making a successful crystal radio for maximum performance, is a good set of sensitive high impedance headphones. This kit allows the use of common low impedance earbuds (like Walkman style) to work with high impedance audio output circuits found on crystal radios without loading down the circuit resulting in loss of sensitivity or selectivity. Just plug in your inexpensive 3.5mm earbuds into the pcb and attach two wires from the adapter binding posts to the headphone connections of your radio. It is similar to the HZX Headphone Adapter featured in the article by the ARRL, but runs on a CR2032 coin battery and has adjustable gain. It can be easily moved from radio to radio. A battery will last over 1,000 hrs. of continuous use, due to the very low current draw of the circuit. The pcb is just 2″ x 2 1/8″.
It can be purchased as a complete tested assembly, less battery, or as a kit, less battery, or only the bare board and transformer. You would need to source the easily obtainable components from Mouser and/or Tayda for the last option.
The tools required for the kit are a soldering iron with a small tip, rosin core solder, small side cutters, and can be built in less than an hour, depending on your experience. On a difficulty scale of 1 to 5, 5 being the most difficult, this is rated at 2.
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