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I am using a small audio player board (DFPlayer Mini) that has a 3w audio amplifier built in. I have hooked it up "as is" and it appears to work but has some intermittent static. While it could be due to a loose wire, in the process of checking it out I noticed that the impedance is 67 ohm, not the typical 4 or 8 ohms.

Is there any circuitry I should add to protect the audio player and/or speaker?

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  • \$\begingroup\$ In theory a matching transformer would be possible, but it's not a ratio you're likely to find. This is probably not the source of your actual issue. \$\endgroup\$ – Chris Stratton Jul 26 '19 at 0:46
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An audio amplifier will in most cases (modern boring designs, not tubes or esoteric amplifier topologies) not be harmed or have any difficulty with a higher impedance than typical. The output is approximately a voltage source, so a higher load impedance means less current flows. No big deal (unless it's too quiet).

If you want to be sure that you're using an appropriately designed amplifier for the application, choose one intended for headphones — impedances on the order of 67 Ω are entirely normal for headphones. Headphone amplifiers are also designed to suit the application by having lower noise (since you're putting your ear right up to the speaker).

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  • \$\begingroup\$ Excellent, thanks Kevin! \$\endgroup\$ – Mark Stevens Jul 26 '19 at 13:08

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