Electrical – Using two mono amplifiers to make one stereo amplifier

amplifieraudiodaci2spcb

On my PCB (connected to a Raspberry Pi, an Arduino, a C.H.I.P. or anything), I want to provide audio output for:

  • a small speaker
  • or, when a 3.5 mm minijack is inserted, to stereo headphones (that would disconnect the speaker)

Instead of using

board ==(I2S)==> DAC => amp => speaker or headphones

I was thinking about :

board ==(I2S)==> amplifier such as MAX98357A => speaker or headphones

Problem : this MAX98357A seems to be mono only. The datasheet suggests using two of them to make a stereo output, but I find it not very elegant solution.

Are there "all-in-one" (DAC+amp) solutions to provide stereo output? (I'm not looking for shopping advice, I just want to know if, as a general question, this exists or not).

Would using two such mono chips be considered as a normal practice?

The datasheet carries this example:

MAX98357A datasheet: dual-IC stereo

Moreover, this MAX chip looks hard to solder manually (SMD). Do you think this kind of SMD soldering is achievable manually?

Best Answer

Such chips exist:

http://www.analog.com/media/en/technical-documentation/data-sheets/ADAU1373.pdf

There's one in every cellphone... however the real problem will be finding them in a package that isn't some microscopic variant of BGA.

Please note that I2S sends both channels on the data line, and the WCLK line distinguishes left and right channel. If you use 2 chips, like in your schematic, your chips need to be aware of this and be able to extract the proper channel from the I2S stream. The ones you quoted are able.

The ShutDown/Mode pin can be used to put the chip in shutdown or set up which I2S audio channel is piped to the speaker. By default, the amp will output (L+R)/2 stereo mix into mono out. By adding a resistor, you can change it to be just left or just right output

I suggest using DigiKey search tool, search for codecs/dacs, with headphone amp in the features, and filter by package maybe.

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