[sdiy] help me not electrocute my friend real quick -

[cheater cheater]

> Without a transformer if the amp accidentally shorts line voltage
> onto one of the mic wires you could get shocked.  The suggestion
> to plug the amp into a ground-fault interrupter (GFI) protected outlet
> is probably adequate - no transformer required.

Capacitors and transformers can produce strong currents after the
interrupter is tripped.
Theoretically you can die.

As far as the experiment goes: I'd be more concerned with whether the
microphone will stand the crushing pressure of the frozen water. And
even if so - I think the piezo would be so crushed it wouldn't pick up
sounds anymore.
Maybe try putting it in a small plastic bag that has an air bubble
inside it. That air bubble will get compressed as ice forms; the
plastic bag will conform and so will the air. The mic will be
operating at a higher pressure, and we all know that pressurized air
cavities allow better reproduction around DC, so hey, bonus.

On Tue, Jan 27, 2009 at 4:06 AM, Dave Manley <dlmanley at sonic.net> wrote:
> With a transformer the only coupling is magnetic, isolating the mic
> from any current paths through the amp.  You'd want the transformer
> near the amp, at the far end of the cable from the mic.
>
> Without a transformer if the amp accidentally shorts line voltage
> onto one of the mic wires you could get shocked.  The suggestion
> to plug the amp into a ground-fault interrupter (GFI) protected outlet
> is probably adequate - no transformer required.
>
> If the ice is in a plastic jug or bucket on an insulating surface there's
> really not much risk anyway.
>
> -Dave
>
> Horton wrote:
>>
>> Why hook it up to a transformer?
>>
>> AH
>>
>>
>>
>> On Mon, Jan 26, 2009 at 7:20 PM, HL-SDK Synths <syntroniks at gmail.com>
>> wrote:
>>
>>>
>>> As long as the amplifier that this is being connected to doesn't fail,
>>> there
>>> is no real risk. The input is an input, and should accept signal from the
>>> piezo, rather than try to hurt anyone. I think you (or your friend) will
>>> be
>>> pretty satisfied with the results. I can almost guarantee good sounds.
>>> Waterproofing is a _VERY_ good idea as well. Now that I think of it, I
>>> wouldhook it up to a radioshack transformer.
>>>
>>> One with 1K to 8 ohm impedance. Something therabouts.
>>>
>>> On Mon, Jan 26, 2009 at 7:04 PM, Horton <horton.andrew at gmail.com> wrote:
>>>
>>>>
>>>> I'm about to build my friend a contact mic. I found instructions here
>>>> - http://brokenpants.com/?page_id=94 - and I have a few spare piezo
>>>> elements hanging around, so I figure it's a quick job, no problem.
>>>>
>>>> However, she specifically wants to freeze this mic in ice and use it
>>>> to record the sound of the ice cracking as it melts. I figure I'll
>>>> just dip the entire piezo end in plasti-dip, let it dry, and she's
>>>> good...waterproof. Will that be fine? I have no idea what she'll be
>>>> plugging it into on her end, but whatever it is, it's coming off of
>>>> wall power and not batteries.
>>>>
>>>> AH
>
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