I added a loudspeaker to my QCX+ to make it easy to keep up with band activity while pottering round the shack, rather than being shackled to headphones.? I must say I find that using a loudspeaker makes operating much more convenient than being forced to rely on just headphones.
The design is nothing fancy - just the ubiquitous LM386N 8 pin DIP chip from Texas Instruments feeding a 50mm diameter loudspeaker. The amplifier (built on a piece of stripboard) and loudspeaker are fixed to the upper part of the QCX+ case, with some 5mm holes above the speaker to let the sound out. This chip can produce around 250mW into an 8 ohm load, which is plenty loud enough in most environments.
The loudspeaker amp is powered from the switched +12V supply at JP27(3) and gets its input from the back contacts on the headphone jack at JP18 (pins 2 and 3). This means that the loudspeaker is turned on when the headphone jack is pulled out (although there is a mid-way position where both phones and speaker are on).
Below is a circuit diagram with a couple of photos. I will put more detailed design notes in the "Files" section.
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Peter Lee
G3SPL
