two questions on modifying my Cortado mkii

[Philip]

I just got my kit and am really excited to get started on building the thing. Before I start, I have two questions about modifying and finishing the contact mic. I’m handy but don’t know much about electronics so these are sort of ‘why can’t I do _’ types of question that a more experienced builder would at least have some opinions about.

First, I wondered if I might use XLR plugs to connect the contact mic itself to the preamp part so I could swap out the thin piezo disc for, say, the sensor upgrade without having to rewire the thing?

Second, I’m a big fan of the suggestion in the guide of using plasti-dip to insulate the piezo before applying the grounding copper tape. Is there a reason I couldn’t or shouldn’t use another layer of dip after shielding the piezo?

Thanks in advance for your time and knowledge!

[brach]

Philip,
Thanks for the questions…
I don’t recommend using a jack/socket for the piezo connections because of its very high impedance. Jack connections will get oxidized over time and that will limit its conductivity. When dealing with extremely high impedance devices, the tiniest bit of resistance on their connections will severely degrade the signal. Remember, high impedance devices have lots of voltage but hardly any current to push through impedances in the signal path. That’s why it’s always best to use hard wire connections in dealing with piezo sensors.

There are some complications involved with using Plastidip to insulate the disc. The main thing you need to be mindful of is that the dip will flow away from the edges of the disc causing this area to be susceptible to electrically connecting with the copper tape. This also causes the disc to be slightly domed shaped or beveled. These days I suggest using electrical tape or Kapton tape. But to answer your question, you can use plastidip to coat the disc when it is finished. If you coat it well enough, it will be waterproof and can be used as a hydrophone.
I hope this helps. Good luck!
-Brach

[Philip]

Thanks for the advice! I’ve learned a lot and will be sure to keep it all in mind.

[Author]

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