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The GDP2846A module has an in-built 2W amplifier which is fine for a small speaker but not for a pair of headphones as it is indeed way too much.

I've thought of directly taking the DAC outputs (before the amp) to the headphones and call it a day as I've seen people doing with their ESP32s. This would allow me to have both headphone output and speaker which is the ideal result.

But I am not sure it is a good idea. Resistors to turn down the power when using headphones will waste a ton of precious power which due to the small battery is unacceptable. Is my only option to use an external op-amp (which would complicate things a lot and I want to keep things as simple as possible) or is there an easier way out?

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    \$\begingroup\$ What makes you think that 2W is not enough for headphones? It sounds like plenty to me. In any event, please include a link to the manufacturer's datasheet for the module. \$\endgroup\$
    – Elliot Alderson
    May 16 at 18:48
  • \$\begingroup\$ or do you think it's too much? But that would betray a misunderstanding of what an amplifier does! \$\endgroup\$
    – Marcus Müller
    May 16 at 19:58
  • \$\begingroup\$ @ElliotAlderson I mean it is way too much. A headphone uses roughly 0.1watt \$\endgroup\$
    – Παναγιώτης Θ
    May 17 at 19:43
  • \$\begingroup\$ @MarcusMüller yes I mean it is too much. Headphones from what I know require about 0.1 watts each. Ideally, the project would have a 2W speaker output and a line level output for headphones which I'm not quite sure how to implement \$\endgroup\$
    – Παναγιώτης Θ
    May 17 at 19:45
  • \$\begingroup\$ you're indeed confused about what an amplifier does! The problem you think there is not a problem. An amplifier doesn't "constantly output" 2W. The amount of power it supplies depends on the impedance of the attached speaker/headphone. And with a 8Ω wideband speaker you get way more power than with a 32 Ω headphone speaker. \$\endgroup\$
    – Marcus Müller
    May 17 at 19:47

2 Answers 2

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2W refers to the maximum power the amplifier can put out at 100% volume. Into typical headphones this would be about 15dB louder than something like an iPod, but you can compensate by lowering the volume to reach a comfortable level.

That said, that spec sounds exaggerated, since they claim 2W into 4 Ohms (~8V) but only use a 5V power supply. Quite likely the output is similar to normal headphone output.

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I could not find detailed specs for the module or for the ICs on it (the numbers were erased on the Amazon module). The "2W" amplifier has a + terminal and a - terminal so it is probably bridged (an amplifier on each speaker wire with no ground). Then the output produces 8Vpp which is 2.83V RMS or half that (1.414V RMS) into each speaker wire. Then the maximum power into a 32 ohm earphone is 62.5mW which is not too loud. Connect a series coupling capacitor to each speaker output wire for feeding each grounded earphone.

The amplifier has a single mono output but one datasheet of the decoder has left, right and center. Does anybody play mono into headphones?

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  • \$\begingroup\$ You are right, no-one plays mono on headphones, hence my idea to take the DAC_L and DAC_R to have stereo as well on headphone mode. To my 16Ω headphones it is double the milliwatts? \$\endgroup\$
    – Παναγιώτης Θ
    May 18 at 8:50
  • \$\begingroup\$ The module has a 2W power amplifier on it that produces 2W per channel into one mono 4 ohm speaker or 62.5mW onto 32 ohm headphones. The DAC probably cannot drive headphones since it is designed to drive the high input resistance of a power amplifier. \$\endgroup\$
    – Audioguru
    May 19 at 15:55

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