Question Audio Amplifier for speakers and headphones?

Discussion in 'Nintendo 64' started by Lab Minion, Aug 29, 2019.

  1. Lab Minion .

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    I'm working on the audio amplifier for my portable N64. Currently, I'm experimenting with this PAM8403, and have made it drive some 8 Ohm speakers I had laying around. I would like to integrate a headphone jack that disconnects the speakers when plugged in. I am experimenting with this headphone jack switch . I can get it to disconnect the speakers, but one headphone speaker is weaker than the other and both are greatly distorted compared to the speakers.

    I suspect that is is because the PAM8403 isn't designed for 32 Ohm headphones, or I need some coupling capacitors or similar. Any thoughts?

    Are any of you using other/better solutions to add a speaker and headphone switch option? EG: TDA2822M, PAM8009, so on. I've been looking for a complete solution (1-3W, vol control via thumbwheel, speaker out port, headphone out jack) that I can just drop in, but can't find any yet.

    Thank you for your help and pro tips!
     
  2. Stitches 2 and a Half Dollarydoos Staff Member . .

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    It's not quite "drop in", but JacksonS' custom amp does all you're looking for, even the option of a volume wheel/slider instead of digital buttons.

    Second last in this list https://oshpark.com/profiles/JacksonS

    If you don't have the equipment/knowhow to assemble one there are a few people here who could do it for you for a price.
     
  3. Lab Minion .

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    Thank you for the help, I appreciate it! I will consider that if I can't seem to sort out a pre-built, off the shelf amp.

    After some experimentation I did get three different amp boards working with both speakers and headphones (PAM8403, LM4853, and a TDA2822M). But, my headphone shielding is not grounded as it should be. If I ground the shielding, when I plug in the headphones I lose the right channel. If I leave the shielding floating, both channels work fine on the headphones.

    Do I need some sort of voltage divider to "pullup" the right channel as is discusses here: https://sound-au.com/project100.htm ? Or am I missing something else?
     
  4. cheese the tallest memer in town Staff Member . . .

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    Not sure where you see them pulling anything up? That post is using resistors to pull down the voltage going to the headphones, lowering the overall voltage and volume. Got pics of wiring? Maybe you have something wired backwards...
     
  5. Lab Minion .

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    Thank you for the reply! I was building a diagram for you to review and figured out that I reversed the R-channel legs on the headphone switch. Sigh...

    It works now, but 3W is too powerful/loud. Does anyone have a better amp that hovers around the 1-2W range for a speaker+headphone application? I tried Adafruit's MAX98306 and TPA2012 since the wattage at 8 Ohms is around 1.5W, but the outputs are bridge-tied so doesn't appear to work with a common ground on the headphone jack+signal out.

    I suppose I could use the PAM8403 and put series resistors in line with the signal in, but that would just waist power.

    Thoughts?
     

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