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I want to build a small projekt for with just an Arduino, a radio receiver and 2 speakers.

I have bought a small PCB with a TEA5767 radio FM chip (ebay). The audio output is however fed directly in a headphone amplifier chip TDA1308 from NXP (datasheet). The rated maximum power output of the TDA1308 chip is 80mW.

I want to however feed the audio into two speakers. For this purpose I'd like to use the PAM8403 stereo audio amplifier (datasheet). This chip is rated for 3W output power.

Would it damage the amplifiers or the speaker if I were to connect the output of the headpone implfier to the input of the speaker amplifier? If yes, what's the best way to get the audio to the speakers? Should I convert the amplified signal to line-level again and then amplify it again? Or would be easiert to just desolder the headphone amplifier and grab the TEA5767's audio output directly?

I've searched for similiar questions on this board but nothing came up. Thanks for your help.

chippies

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  • \$\begingroup\$ It possibly is fine, but you should check the datasheet of the manufacturer of the PAM board. You might need to add a resistive divider to lower the voltage from the FM radio to the PAM board. \$\endgroup\$ – Vladimir Cravero Aug 30 '17 at 12:53
  • \$\begingroup\$ Depends on how much imput impedance your audio amplifier chip has. If my memory serves me right, most of them have 600 ohm input impedance (is/used to be a standard in audio). Note that your headphone amplifier needs to be ok with driving such a load. \$\endgroup\$ – Joren Vaes Aug 30 '17 at 12:58
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Thanks for the suggestion. Daisy chaining actually works pretty good. I added two potentiometers for volume control, 50kOhm each. Nothing gets hot and it's running since 10 minutes.

schematic

simulate this circuit – Schematic created using CircuitLab

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    \$\begingroup\$ Good work. Did you forget to add GND symbols at the bottom of R1 and R2? If your own answer is correct you can "accept" it to indicate that the question is answered. \$\endgroup\$ – Transistor Feb 24 '18 at 8:05

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