Re: [EE] DAC-to-headphone-level output amp
Neil <[email protected]>
| Newsgroups | gmane.comp.hardware.microcontrollers.pic |
|---|---|
| Message-ID | <[email protected]> |
So I ended up trying this -- connected an STM32 GPIO output to the BLE transmitter via a series cap (used 1uf as that's what I had on hand with leads) and it worked quite well. So that's the route I'll go (without any op-amp). The STM32 output was 2.92Vp-p unloaded and loaded (with the BLE input connected), so it seems the BLE transmitter has a fairly high input impedance. Thanks, -Neil On 12/22/2024 11:53 PM, Neil wrote: > Yes, will try this. Thanks > > > > On 12/19/2024 7:59 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. >>> >>> >>> -- >>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >>> View/change your membership options at >>> https://mailman.mit.edu/mailman/listinfo/piclist >