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I have headphones with differential input and impedance of 8 ohms. I need to drive this headphone with some DAC with built in headphone driver (Currently I have chosen ADAU1772). DAC's datasheet mentions that the minimum impedance of headphones it supports is 16 ohms. Can I increase impedance of my headphones so that I can drive them through this chip? What will happen if I drive this 8 ohm headphone through a chip supporting minimum impedance of 16 Ohms?

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  • \$\begingroup\$ Have you already asked this question here? electronics.stackexchange.com/questions/308230/… \$\endgroup\$ – Colin Jun 1 '17 at 10:19
  • \$\begingroup\$ This question differs from the one you have mentioned in that it ask for a method to increase impedance of headphones. The one you mentioned doesnt ask this. \$\endgroup\$ – user3056350 Jun 1 '17 at 10:32
  • \$\begingroup\$ method to increase impedance of headphones That's not what needs to be done. Increasing the impedance means using different headphones. Or you could use an audio amplifier to drive the headphones. You can buy cheap LM386 based amplifier modules which can do just that. Don't forget to load the DAC with the proper resistor it needs, like 30 ohms to simulate the headphones which the DAC expects to drive. \$\endgroup\$ – Bimpelrekkie Jun 1 '17 at 11:23
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You have several choices:

  1. Get a chip that can drive 8 Ω.

  2. Put a buffer between the D/A and the headphones. This buffer must then be able to drive a 8 Ω load. The D/A only sees the input impedance of the buffer.

  3. Use headphones with 16 Ω or more impdance.

  4. Put a 1.4:1 audio transformer between the D/A and the headphones. The D/A output will need to be 1.4x larger than before, but will see a 16 Ω load when 8 Ω headphones are connect to the output of the transformer.

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  • \$\begingroup\$ ... or 5. Just accept the fact that you won't be able to get the full rated power out of the amplifier. The volume level you get may well be sufficient for your application. \$\endgroup\$ – Dave Tweed Jun 1 '17 at 12:52
  • \$\begingroup\$ Whoever downvoted this, what exactly do you think is wrong? \$\endgroup\$ – Olin Lathrop Jun 5 '17 at 10:37
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Nominal 8 Ohms for headphones is not much, and will make the DAC deliver the double current (compared to nominal 16 ohms).

You can not do much about it, as the impedance of the headphones are from the coil. If the impedance of the headphones were only a resistance, you could put a resistor in series (with power loss), but as the impedance is very frequency dependent, you will ruin the frequency responce.

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  • \$\begingroup\$ My main concern is whether these headphones will deliver sound or not if I connect them with this DAC chip? Can you answer that? \$\endgroup\$ – user3056350 Jun 1 '17 at 10:15
  • \$\begingroup\$ I am not qualified to answer that, sorry. Tho a search on google, tells me that it sometimes work, with lowered audio quality. \$\endgroup\$ – keffe Jun 1 '17 at 10:20
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I connected the speaker with 8 ohms resistors in series between headphones differential wires and dac output. I was getting a hear able sound. I removed resistors and connected the headphones directly, the voice got louder. However my application was outputting only male voice and no music. Dac was also not heating up while headphones were directly connected.

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