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Zero AMP 1 #1

Open mbt28 opened 7 years ago

mbt28 commented 7 years ago

Hi,

I have a RPI Zero that I dont use, I would like to use this your circuit to listen music, however can you please tell me using normal headphones with this module is dangerous or not?

Thanks

ywabiko commented 7 years ago

Hi, thank you for the question and interest! Using normal headphones with it would be actually dangerous. PCM5102A is rated like 2.1mA (i.e. 4mW or so). Let's say your headphone's impedance is 32 ohm (typically it is somewhere between 16 to 64 ohm). In this case, your headphone will try to draw too much current like 66mA that will be too much power 135mW. This may break your PCM5102A. Also, it may cause your headphone to emit too loud sound that is loud enough to cause permanent damage to your ear. If you're adventurous, you can try and see what happens at your own risk. Please do not put on your headphone when you power it on or start playing sound. (This is common practice to any audio project, though.) Thanks!

mbt28 commented 7 years ago

Hi,

Thank you for your quick response. I think in this case, and headphone amplifier is needed. What was the reason that you didn't add headphone amplifier?

Thanks

ywabiko commented 7 years ago

Hi, actually I forgot the fact that I put a register (470R) there. It was mainly meant to be an LPF together with the 2.2nF capacitor, but it also limits the current like 2.1V/470R = 4.4mA that is only twice of the rating. Still, it's unsupported range (and may break PCM5102A), but I don't expect immediate fire/smoke:) And yes, this is exactly why you want an amplifier:)

This current version doesn't have an amplifier simply due to space limitation. A good reference is piamp2. The challenge here is how to put all of the components into a Zero-size PCB. And that's what I'm planning to work on! Again, thank you very much for the interest and feedback!

ywabiko commented 7 years ago

Hi, I have updated the schematic. It now uses 1kR as opposed to 470R, for limiting the current to the maximum value. This is tested with an earphone that came with iPhone and it works on my end.

mbt28 commented 7 years ago

Hi,

Thank you for your support. Actually I would like to support your work with a mic extension, do you have any experiences with any I2S adc in RPI? If you suggest me any ADC which already works, I can update your schematics and pcb with a ADC.

Thanks, Mehmet

ywabiko commented 7 years ago

Wow, that's a cool idea! I haven't tried I2S microphone or ADC yet, though. Please feel free to hack this PCB in any way you want:)