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According to a comment at DIY stackexchange:

"...disconnecting a passive piezo speaker that is fed via a transformer could theoretically upset or even damage the electronics feeding it."

  1. How could the lack of a piezo speaker cause damage?
  2. How could a person silence the piezo speaker without simply "muffling" it with tape or similar tactics? (Perhaps replace it with a dummy load? If so, how would one ensure an appropriate load?)
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    \$\begingroup\$ Did you also raise this question to the person on DIY SE? \$\endgroup\$ – Andy aka Apr 7 '17 at 20:11
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    \$\begingroup\$ @Andyaka - No, I thought it would be inappropriate and inconvenient to ask that on the DIY SE. \$\endgroup\$ – Bort Apr 7 '17 at 20:12
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    \$\begingroup\$ Ask the guy who made the quote. Without much more technical detail this is unanswerable. \$\endgroup\$ – Andy aka Apr 7 '17 at 20:14
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    \$\begingroup\$ @Andyaka - Okay I have asked them, however I imagine that a question like this would be quite answerable. For example, if you heard on superuser.se that replacing twisted pair on a network with coax would cause heavy noise to a signal, then I don't think it would be unanswerable on ee.se \$\endgroup\$ – Bort Apr 7 '17 at 20:18
  • \$\begingroup\$ Well, if you want an answer, what the guy said is fine. He used the word "could" and some amplifiers or systems can be damaged this way however, without a specific example to base an answer around, any answer is just speculation. \$\endgroup\$ – Andy aka Apr 7 '17 at 20:24
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Modifying a circuit that you don't understand can be dangerous, so it pays to be cautious. Without knowing all the design parameters you can't be sure that your modifications won't have unintended consequences.

Piezo speakers look like a capacitor to the driving circuit, typically 10~100nF for the elements used in piezo buzzers. If the driver uses a transformer then it may rely on this capacitance to suppress high voltage spikes and/or 'tune' the oscillation to the correct operating frequency. Without a speaker it may produce higher voltage and/or frequency, which could cause interference or even damage the transformer or other components.

However most piezo buzzer circuits do not use a transformer, so disconnecting the speaker won't cause them any harm. Trace the wires from the buzzer back to the driver circuit. If you don't see a transformer there then it should be safe to disconnect the buzzer.

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Without a load on the transformer, the primary is simply an inductor. Inductive loads support voltage swings outside the resistive load line. Forward-biasing of substrate isolation diodes can occur, if amplifier nodes swing below ground. At the other extreme, high voltages cause junction breakdown (or plate arcing in vacuum tube amplifiers).

Here is a resistive loadline for a bipolar device.

enter image description here

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