Does the signal need pre-amplifying?

[riccardo]

Hi,

I have a TPA3106D1 audio amplifier for use in driving a speaker from an AD9837 DDS IC.
https://www.ti.com/lit/ds/slos516c/slos516c.pdf

The DDS only outputs 0.6V p-p max, yet the amplifier input accepts 0 to 4V.

Will I be able to get full power to the speaker with this or do I need to boost the input signal from the DDS to something closer to 4V p-p before connecting to the amp?

 

[crutschow]

With the TPA3106D1 set for it's maximum nominal gain of 36dB (GAIN1 and GAIN2 inputs at logic high) you would need an input of 0.3Vrms (0.8Vpp) to get an output of 40W into an 8 ohm load.

So if you want the full 40W you will need to amplify the signal by a gain of about 0.8/0.6 = 1.3.
But in practice that's only an additional 2.5dB of sound output, so you probably don't need any additional gain.