Monday, May 18, 2009 Zulu
Science: Experiments vs. Wolfram Alpha

This morning I thought about a fun science experiment for kids: Use a laptop with a sound analysis program such as fldigi to use its FFT to measure the audio doppler shift from an oscillator carried aboard an oncoming bicycle or car. If you know the frequency of the audio source and the velocity of the vehicle, you can calculate the speed of sound. Then, having measured the speed of sound, you can use the laptop to sample and display the varying velocity of a vehicle. A GPS might be good for calibrating the initial vehicle velocity measurement.

Or, you could just skip the experiment and do it all in The Matrix.

- posted by Leigh @ 20:44 z 0 comments
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Sunday, May 03, 2009 Zulu
Radio Shack SA-10 Audio Amplifier
I have a Radio Shack SA-10 Audio Amplifier which I use with my Squeezebox. It's surprisingly hard to find a good, inexpensive small audio amplifier with RCA inputs these days; most of the industry now makes amplifiers with proprietary Apple connectors.

This SA-10 has always had an intermittent buzz to it, and a low-level hum. I took it apart and didn't see any obviously blown capacitors, so I did a search and found a quick review article on the Realistic SA-10 Audio Amplifier by Joe Roberts. Joe points out that C108 is perhaps under-rated for its job, so I replaced it with a 50V one I had on hand. We'll see if that takes care of the intermittent buzz.

The power cord is a two-line one that goes directly to a transformer. The hum went away when I grounded the case, so I fashioned a third-wire for it and am now enjoying a bit of the old Ludwig van.


- posted by Leigh @ 19:25 z 0 comments
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