Home made stereo Hydrophone for less than $10

Last weekend I decided to build my first hydrophone. I live on a lake and there are always interesting things going on around and in the water. Having been invited to also work on several art installations themed towards water, rivers and nature, I figured that something missing from my kit was an underwater microphone.

Not wishing to part with too much cash I decided to build my own. This was also because I wanted a stereo mic, and one built to my own specs. One built cheaply would also allow me the luxury of experimenting with several differing versions.
The microphone I decided to build was based on some Panasonic capsules hosted inside a set of stereo headphones, and then smothered in silicone. I also tied a fishing sinker to the mic so that it would submerge and be steadier in the water. I have to say I am extremely happy with my 1 hour build! The sound is so clear... and for only a few $$$.

I also used cable ties to keep both sides locked together so as not to have them hit each other in the water. The sinker is behind, and also held tight so as not to hit the microphones. The advantage of using the cable ties also allows flexibility in adjusting the angle on the microphones.

How some basic electronics can save you some $$$

I wanted to write about how some basic electronic repairs has saved me in excess of $100.

Firstly, I have had a Jim Dunlop Cry Baby guitar "wah" pedal since being a teenager (yes... quite some time). Anyway due to a lack of use, living by the sea and collecting dust my attempt to use the pedal recently was quite futile. The pot inside which creates the iconic "wah" sound had inherited a nasty cheese grating crunch noise, every time I pressed on the pedal! After a quick diagnosis it was apparent that it was just a dirty pot, but a dead pot. Looking around Ebay the replacement genuine Hoy Potz pot was going to cost around $50 AUD. Thinking that this was a bit steep for a part which gets used once a year I decided to test a "non genuine" pot instead. Going to Tandy and ordering a $2.75 part with the same specs had me feeling quite confident. After installing this new pot, my confidence had soared as the sound was identical to the Hot Potz in it's glory days. The only change I had to make was that the nut on the pot has to be tightened as much as possible, as it a slightly smaller fit that the original. But hey, for $2.75 - you can' tell the difference. If you want to know the part I used, it was a 100K ohm linear flat shaft pot.

Whilst feeling confident in this repair, I also had an apple laptop with an external power supply which had frayed cables where the plug inserts into the laptop. Having a second power supply allowed me to simply chop off one cable and splice on another cable (in almost new condition). This doner cable had come from the original power supply. However the power supply decided to internally combust one day after being plugged in for 12 hrs. Many people would simply have thrown these power supplys out and bought another one, however for 10 minutes work I have saved another $50 or so.