Re: [EE] DAC-to-headphone-level output amp

Will try it.



On 12/19/2024 9:35 PM, Harold Hallikainen wrote:
> I wonder if the BlueTooth transmitter already has a DC blocking capacitor
> on its input. If the circuitry in the BT device is single ended, it
> probably DC blocks and then biases to the ADC midrange voltage. It would
> be interesting to try it with no additional capacitor.
>
> Harold
> The ideal design has zero parts.
>
>
> On Thu, December 19, 2024 5:59 pm, [email protected] wrote:
>> For a one off I would try direct drive the BLE from the DAC via a 10uF
>> capacitor and work out where to go from there.
>>
>>
>> Cheers,
>> Martin.
>>
>>
>> On Friday, 20 December 2024 at 09:58, Neil <[email protected]> wrote:
>>
>>> I'm designing a one-off device for myself that will generate audio from
>>> a microcontroller and I want to send that audio to a small BLE audio
>>> transmitter (something I picked up on Amazon).
>>> The BLE transmitter has a 3.5mm headphone plug and they specify it's for
>>> "Aux" level devices, but works very well when plugged into my PC or
>>> cellphone, so I take that to mean headphone level.
>>> FWIW, the audio signal is mono, but I want to drive both left and right
>>> channels.
>>>
>>> Researching online gets me a whole lot of different answers --
>>> everything from line level being 10k ohms input impedance and 1V or 2V
>>> to 3V and headphone level is 8 to 600 ohms, with voltage level from 0.3
>>> to 0.8V (though I would've expected headphone level to be higher since
>>> it's amplified).
>>>
>>> Can anyone shed some light on this please. I'm unsure what I'd be
>>> designing for... should I just do an op-amp with a very low output
>>> impedance and adjustable volume until it sounds decent? Or is there a
>>> spec I should follow?
>>> Alternately, I'd be happy if there's some simple monolithic chip that
>>> would do this for me (take a 0V-3.3V audio signal from a uC DAC and
>>> convert it to headphone level audio).
>>>
>>> Cheers,
>>> -Neil.
>>>
>>>
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>