Work continues to progress. Less musical activity this week, but more learning (thanks to Bruce Larson!) about regulated vs. linear power supplies, multimeters, and DC/DC converters.

Regulated vs. linear: a linear AC/DC converter (those large “wall warts” that we use to power electronic devices) may be labelled with a particular voltage, like 12V…but in reality, what the converter is actually delivering is 12V or lower, depending on the draw. Often, that doesn’t matter…but when it comes to amplifiers and audio, it’s a deal. So, as I mentioned last week, I decided that it was time to start working with my motorcycle speakers rather than headphones. The amp requires 10-16 volts, a range that is typical for a motorcycle battery. When I set them up and powered them on, using a 12V DC adapter, I heard an awful, painfully loud distorted sound. I thought I had damaged the speakers by leaving them in the trunk of my car overnight, or that perhaps I had blown a circuit in the amp. As it turns out, the converter was delivering only 7V when powered on, or when the volume was turned too high. As this was below the 10V threshold, the amp ceased to function properly. So, I need a regulated power supply, which delivers the rated voltage no matter what the draw. As Bruce explained, these converters are easy to spot, or rather, weigh–they are much lighter than linear supplies.

Multimeters: after much reading and research, I’ve decided to invest in a Fluke multimeter. They are more expensive but are quite robust and last for years. The one that Bruce owns is now over 20 years old and is still going strong. Because of their quality, he also advised that it’s ok to buy used, which is good–the bottom-of-the-line Fluke currently retails for around $150. So, I’m currently scouring ebay for a used 115 or 73 model, which it looks like I can procure for around $50.

DC/DC converters: The battery supply will be 12V, but the Raspberry Pi needs 5V. Thus, a step down converter is in order. Apparently, these are rated in terms of efficiency–if it says “90%,” ostensibly, this means you are conserving 90% of the extra voltage you are discarding. Such a conversion, from 12V to 5V, often happens in cars and other vehicles.

Here are two additional sound files, “water” and “birds”:
Water
Birds