sudomod

I'm just wondering how do you usually connect your headphone jack? Do you connect it from the audio amp or just directly to the pi or usb sound card? Why?

I guess i want to know if directly connecting it to the PWM pins on the pi zero is enough for using earphones. On my recent pi 3 build, the headphone jack is directly connected and earphones sound volume is good enough but im not sure if it's ok on the pi zero.

What about the low pass filter, does it really help based on your actual experience?

Thank you.

tinkerBOY wrote: ↑

Sun Nov 26, 2017 11:14 pm

I'm just wondering how do you usually connect your headphone jack? Do you connect it from the audio amp or just directly to the pi or usb sound card? Why?

I guess i want to know if directly connecting it to the PWM pins on the pi zero is enough for using earphones. On my recent pi 3 build, the headphone jack is directly connected and earphones sound volume is good enough but im not sure if it's ok on the pi zero.

What about the low pass filter, does it really help based on your actual experience?

Thank you.

Hi, the raspberry gpio pins have a current limit. Most sources say 16mA per pin, but only 50mA in sum.
Links: https://www.element14.com/community/thr ... hread=true
https://raspberrypi.stackexchange.com/q ... -3-model-b

The very popular Rock Zirkon Earphones (https://de.aliexpress.com/item/Original ... 06316.html) use 3mW. The GPIOs use 3,3V, (P=U*I) so its 3mW=3,3*I => I = 3mW/3,3 = 0,91mA. So that should be fine even if the lowpass filter draws some power.

On the raspberry 3 the following circuit is used:
https://learn.adafruit.com/assets/28850 (from: https://learn.adafruit.com/introducing- ... io-outputs)
It uses a buffering op amp (http://www.onsemi.com/PowerSolutions/pr ... id=NC7WZ16) which drives the headphones.

I don't know why the raspberry foundation uses this ampifying op amp. It think it is for greater on ear headphones, which use more power. Or it sounds better than the gpios alone. Maybe someone with audio knowledge can contribute to this a little bit more.
Or it is used because DC voltage on the GPIO PWM pins will destroy your headphones.

Hope I could help you.

I go amp>headphone jack>speaker. Mostly because the way the components are laid out, amp in one bottom corner, headphone jack in the middle and speaker in the other corner.