A new radio to listen to news in the kitchen, play music from my library of MP3s from an SD chip, AND it has an AUX input for an iPod.

Due to the mysteries of modern consumer product distribution, the whole radio costs less than a single DIY amplifier chip at Fry’s.

But there were a couple of surprises inside the radio. Cost reductions, they say ...

Done. Grab a pair of the 5 inch “Iced Tea” speakers. Nice! It’s certainly a few notches above the old clock radio. Not audiophile by any means, but better than one of those bluetooth speaker thingys. There is actual bass, not just lower midrange thumps. Plenty of power for the purpose, tho nowhere near what is claimed on the box.

Take it apart to drill holes. Bolt stuff in. Solder some wires.

So let’s turn it into a kitchen radio & music box. First, what have we got lying around in the parts boxes? Well, there’s a Radio Shack 25V C.T. power transformer. We’ll use it + a couple of diodes and caps from the big box of electrolytics. That’s our 15V power supply. Then we need something easier to connect speakers than the multi-pin plug of a car radio. Binding posts for speakers and antenna. Some rubber feet. That’s about it.

Therz nothing in here! Three chips on the rear PCB, a 4-channel linear power amp rated for 4X 4W into 4 ohms; a digital preamp / control chip which does the usual car radio functions, volume, balance, F/R fader, bass, treble, loudness, etc.; and a 16-pin DIP which is a complete digital FM tuner. The front panel remains a mystery - I didn’t pry it apart to look at the chips in there - it’s glued together.

Since the channels of the amp chip aren’t being used in pairs to make a balanced output, and the output is at half the power supply voltage, there must be output coupling capacitors, right? But no, there aren’t four largish electrolytics, there’s only one. Turns out, the 4 speaker outputs come out directly and at 7V above ground, and all four speakers return to a common capacitor to ground. The front and back amplifiers are out of phase so some of the ground current will cancel out. Hmm, that means if I connect my two speakers from front negative to rear positive, I get a BTL output and extra power. Front positive and rear negative outputs are simply grounded via that 220 mF electrolytic cap. I should also get better bass response without that somewhat skimpy cap in the speaker circuit. SO that’s how I wired it up. If you buy one of these super cheap car stereos, check for this kind of short cut. And don’t expect to get four channels of 40 watts each out of a chip rated at 20 watts max total. But then you already know better than to believe spec sheets of cheap gear, don’t you?

I’m happy. 8 watts per channel is plenty for my kitchen, the radio works well, and MP3s sound good. What’s not to like? But I still wonder how they do it for $9.99 ...