Hello all,
I'm working on an amplifier based on the TDA7294. It has a built-in mixer with three inputs (based on the CircuitLib article here: https://www.circuitlib.com/index.php/tutorials/product/39-how-to-build-an-audio-mixer). I also need the amp to have a phone jack. At the moment, I have two thoughts on how to accomplish the headphone output - see images attached (don't worry about missing resistors, caps and the like... this is just a concept diagram).
Option #1 - Use a passive voltage divider on the output of the main amp
Option #2 - Build two parallel amplifiers, one based on the TDA7294 for the speakers, and a second amp based on the LM386 - an independent switch in the phone jack will activate the mute function of the main amp when phones are plugged in.
I'm leaning towards Option #2 for several reasons: 1) I'm skeptical about relying on the internal ring switch of the phone jack for audio fidelity, 2) this allows for independent volume control of the two outputs, 3) (and most scientifically), well... it seems a better way.
Note - the selection of the LM386 over something like the LM4910 is due to power requirements. My amp already has two sets of power rails - a +/- 36V for the main amp, and a +/- 12V for the op amps. I can use the 12V rails for the LM386, the LM4910 would require more work to provide a 6V power supply.
I'd appreciate your thoughts or comments or options I've not considered.
Thanks.
I'm working on an amplifier based on the TDA7294. It has a built-in mixer with three inputs (based on the CircuitLib article here: https://www.circuitlib.com/index.php/tutorials/product/39-how-to-build-an-audio-mixer). I also need the amp to have a phone jack. At the moment, I have two thoughts on how to accomplish the headphone output - see images attached (don't worry about missing resistors, caps and the like... this is just a concept diagram).
Option #1 - Use a passive voltage divider on the output of the main amp
Option #2 - Build two parallel amplifiers, one based on the TDA7294 for the speakers, and a second amp based on the LM386 - an independent switch in the phone jack will activate the mute function of the main amp when phones are plugged in.
I'm leaning towards Option #2 for several reasons: 1) I'm skeptical about relying on the internal ring switch of the phone jack for audio fidelity, 2) this allows for independent volume control of the two outputs, 3) (and most scientifically), well... it seems a better way.
Note - the selection of the LM386 over something like the LM4910 is due to power requirements. My amp already has two sets of power rails - a +/- 36V for the main amp, and a +/- 12V for the op amps. I can use the 12V rails for the LM386, the LM4910 would require more work to provide a 6V power supply.
I'd appreciate your thoughts or comments or options I've not considered.
Thanks.