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Single DAC, Multiple Amplifiers?

Other Parts Discussed in Thread: TPA3112D1

I have a design which needs to use 4 x TPA3112D1 amplifiers to supply 4 separate speakers. I want to use one DAC PCM5100-Q1 as the audio source which can drive any combination of the 4 amplifiers which will depend on the /SD state of the amplifier. So, I may want to play a message on just one speaker or possibly on all 4 speakers.

Is is possible to connect the output of the DAC directly to the INP of all 4 amplifiers. So, the INP of all 4 amplifiers will be tied together and supplied from one DAC. What considerations need to be made if this is possible?

  • Hey Joe,

    I can look into this for you. I believe this setup will be possible, but I'll need to double check if the input impedance changes any in shutdown modes. Do you plan to use all 4 amps at the same time from a single DAC? or will only one be one at a time? If you are driving all 4 at the same time, each one would get one fourth the current so your output capabilities would be pretty diminished.

    I'll let you know as soon as I get some more information,

    Nate

  • Hi Joe,

    You should be able to use the DAC to drive all 4 amps via 4 DC block caps.

    reg,

    Paul.

  • Hi Nate, 

                     thanks for getting back to me. The plan was to have the speakers selectable by enabling the required amplifiers using the /SD pin of each amplifier. So any combination of speakers could be selected including all 4 playing at the same time. Would I need to buffer the output of the DAC for each amplifier somehow or would 4 DAC's make more sense, with the data inputs of the DAC's tied together maybe.

    Looking forward to what you find out. Thx

  • Thx Paul, are there any examples of this in a design or application note. I'm just wondering what type or value of caps might be used.

  • Can anyone shed some light on how a single DAC can be used to drive multiple Amplifiers. The amplifier which can be either on or off depending on usage and can be dynamically changed. So, could have 1 amplifier enabled for a particular sound and then enable all 4 amplifiers for a different sound.

  • Hi Joe,

    The sizing of the input DC blocking cap will depend on the bass response you desire and the input impedance (depends on the gain setting) of the amp. There is a section in the datasheet that describes this more in details and some examples.

    reg,

    Paul.