Remember when mixing to go around the sides of the cup, like you're trying to get the last bit of peanut butter out of the jar. Then when pouring, try to pour from the center (like, the main flow should be from the bulk liquid, not from the walls......its hard to explain if you're not familiar with pouring materials......youll see what I mean after a few times pouring your casts), these tricks will keep from getting unmixed sticky half kicked if at all goo in your molds. Remember to get the bottom of the cup too. If there are worrisome bubbles, try to pour in a thin ribbon or a very narrow string (but dont let it break!!! keep it a solid streamer otherwise drips will grab more bubbles when they hit the surface), the thin membrane over the lip plus the shear in the flow should push most bubbles out. Also, cheap and easy releases are hairspray, clear coat, and/or regular, no frills or fluff, Dawn dish soap. Dawn is magic, itll get silicon to kick, and is a billion times cheaper than the recommended hexane and paraffin wax release. Particularly in California..... oh, and especially if using smooth-on resin kits; if you're having a problem with your resin CONTACT THEM FOR ADVICE!!! They are serious about their products (because A LOT of industry hinges upon their products working as advertised and instructed), and they are turbo nerds about the chemistry. If they have a bad batch, or could clarify their instructions better, theyll want to know about it. So, if anyone uses any smooth-on product and its not quite performing as expected, contact them. They like hearing how their products are performing!
If only I waited another week! I just built my first pair of your Hydrophones last week, but I didn't know if I needed to cap the ends of the piezo. That's ok though, they still sound great! It would be awesome if you shared the sound files from your initial test, that way we could drop them into our DAWs to compare the previous version to the new version! Thanks!
awesome! I was looking forward to the update. I hope to make a pair myself in the near future. great that you added the piezo cilinder to your website now aswel.
@@SoundSleuth It's been awhile. I was at Fleet Sonar School Key West in nov 1972- sept 1973. There was a class of ten of us Coasties that went through A1, BE & E, A2 and C shool together. Key West shut down FSS in mid 1974 and shifted all sonar schools to Sand Dawg.
@@tomtrenter3208 I was a Navy Nuke on three different submarines. I hung out a lot in Sonar on my final boat SSN 750. Just listening to the ocean go by!
Reference 10:30 ..... were you able to strip the epoxy off the ones you got wrong? Looking at it it seems like a dremel could possibly salvage the printed circuit board.
@@SoundSleuth The Coast Guard trained us while at FSS Key West how to use Dremel type tools to chew through epoxy conformal coating on printed circuit boards to replace bad components. It wouldn't be easy but theoretically may be possible.
Keep in mind for any serious pressure, any air void or compressible region will cause the hydrophone to be damaged. If you need to take your hydrophone to depth, definitely don't cap the ends of the cylinder, and make sure you very thoroughly degass your resin before pouring (maybe after as well if possible).
Can I assume that the P48 version will work just fine with 12v or 24v (rather than 48v) phantom power for those devices that can deliver it? Having a Zenner drop 48v to 12v worries me.
It will work on P24 as well. The zener doesn't drop 48 volts. the P48 standard supplies 48V via two 6.8K resistors on Pin 2 and Pin 3 of the incoming XLR. Then my circuit further current limits them with two 2.2K resistors. Those limit the current to the zener which is selected by its power rating. This whole circuit is based on my Op Amp impedance converter for condenser microphones. See this: www.instructables.com/OPA-Based-Alice-Microphones-a-Cardioid-and-a-Figur/ Also almost every condenser microphone with a FET uses this same topology.
@@SoundSleuth OK I think it's just terminology here. Without the zenner, 48v is delivered to pin 8 of the opamp. With the Zenner in place that rail drops to 12.6v (in my circuit). The other 36v doesn't just disappear and there are limits on what the zenner can take (I assume it's power rating)! Is the zenner power rating based on the 36v 'loss' and the current? (I only know enough about electronics to be dangerous as they say) Would a 1W 12v Zenner work here?
@@davidh1187 Actually without the Zener, the Opamp sees 48V minus the drop across the two 6.8K resistors in the mic preamp or recorder that supply the 48 volts. As this circuit is when connected you get about 22V on Pin 2 and Pin 3 of the input because of the quiescent current draw of the op amp (and residual rest of the circuit). The use of P48 and a Zener for regulation in mic circuitry is about 60 years old. en.wikipedia.org/wiki/Phantom_power
