Hey, all :-)
I am building a project based on a Feather RP2040 that emits audio (via the audiopwmio library and an Adafruit MAX9744 amplifier) and I've got it working fine, but I'd like to be able to work on it without bugging my wife, and use headphones some of the time.
I found this page from "TodBot" that then refers to this Twitter thread and this little circuit diagram.
This seems quite suitable for my purposes. Anyone have anything different/better/simpler? (Hard to imagine anything simpler!)
Any ideas appreciated!
/rob
Circuit for headphones?
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- sj_remington
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Re: Circuit for headphones?
The circuit linked has high output impedance, and would probably not drive headphones with useful volume.
- robcranfill
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Re: Circuit for headphones?
Ah, yes, I see now that, of course, that is just a line-level output, suitable for input into an amp of some sort.sj_remington wrote: ↑Thu Jan 19, 2023 2:17 pm The circuit linked has high output impedance, and would probably not drive headphones with useful volume.
Any ideas how to drive a set of headphones? I've looked here at Adafruit but see no modules with headphone out.
- robcranfill
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- Joined: Wed Feb 13, 2013 4:14 pm
Re: Circuit for headphones?
Could I use an Adafruit stemma speaker by un-hooking the speaker and wiring in a headphone jack? That is, just using the amplifier part of this breakout?
- sj_remington
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Re: Circuit for headphones?
If you don't want to use the 20W amplifier with the headphones, this tiny stereo breakout would work: https://www.adafruit.com/product/987
It is a good idea to use a voltage divider when connecting headphones to an audio amplifier designed for speakers. Overview here: https://[email protected]/h ... p-adapter/
(REMOVE the @ in the link, added to get around the forum censor).
It is a good idea to use a voltage divider when connecting headphones to an audio amplifier designed for speakers. Overview here: https://[email protected]/h ... p-adapter/
(REMOVE the @ in the link, added to get around the forum censor).
- robcranfill
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- Joined: Wed Feb 13, 2013 4:14 pm
Re: Circuit for headphones?
I think maybe you are under the same mis-impression that I was: the Adafruit 20W amp that I am using does not have any headphone output. The description does repeatedly refer to the “headphone jack” but this is for input, not output. I made the same mistake and was disappointed to realize this after I ordered it. So here I am. :-]sj_remington wrote: ↑Thu Jan 19, 2023 3:19 pm If you don't want to use the 20W amplifier with the headphones, this tiny stereo breakout would work: https://www.adafruit.com/product/987
- robcranfill
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- Joined: Wed Feb 13, 2013 4:14 pm
Re: Circuit for headphones?
I guess ideally, rather than retrofitting a power amp to work with headphones, if I could just create the appropriate circuitry for a dedicated headphone amp, that might be preferable. But thanks for the link!sj_remington wrote: ↑Thu Jan 19, 2023 3:19 pm It is a good idea to use a voltage divider when connecting headphones to an audio amplifier designed for speakers.
- sj_remington
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- Joined: Mon Jul 27, 2020 4:51 pm
Re: Circuit for headphones?
No misunderstanding there. That was why I brought up the resistive dividers. The usual approach is to connect the high resistance end of a divider to each of the speaker outputs, and the taps to the input leads of the headphone jack.the Adafruit 20W amp that I am using does not have any headphone output.
This assumes a common ground, and now that I look at the schematic of the 20W amp, that may not be advisable, as there is none for the push-pull speaker outputs.
Indeed, the best solution is a dedicated stereo headphone amp.
Please be positive and constructive with your questions and comments.