Low power TPA3255 and DSP

I built an active speaker with a 24V battery some time ago, a DSP ADAU1701 and two TPA3118 and it sounded quite good and loud. I wanted to increase its power and I bought two TPA3255 but the problem is that it has not increased as much power as it should and investigating I have discovered which is because the input sensitivity of the amplifier is 2Vrms and the output of the DSP is 0.9V is there any way to decrease the input sensitivity or increase the output of the DSP? Would it help to change the OP Amps? The specific amplifier is this
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I bought two TPA3255 but the problem is that it has not increased as much power as it should...
This is because the 24V battery limits the output power.

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The best resistor to change is the shunt side of the op-amp feedback divider, and maybe the associated capacitor. First you have to identify the op-amps, single or dual? Then draw out enough of the circuit. If I could get a good close-up it would be obvious as the R values are on the silk screen, but without solid information, sorry, I'd probably get it wrong.
 
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Okay, so a couple of things to go over first:

If you're still running the same power supply, you have not much more potential for increased power than with the 3118 chips. The only improvement is heat dissipation of the chip. To get more potential power, we need more supply voltage.

If your 3118 board has higher input sensitivity, it probably gets louder than the 3251 board. I had the same problem with a similar build this year. My board, the shui yuan 3255, has a 10k input shunt and a 10k feedback resistor. I got double input gain from it by finding the input resistor and piggybacking another 10k resistor stop the existing one. My source didn't mind the reduced input impedance, so it worked like a charm. Your mileage may vary.

I have been modifying lots of prefabricated Bluetooth boom boxes lately ( mostly ion brand: game day, party boom, pathfinder, etc.) by doing what you're trying. A common thing between nearly all of these units is that they run a 12V sealed lead acid battery for the power source. The factory chip amps get fed this 12V through a switching network. So what I do with them is rig a 12V relay. Coil to the factory chip amp power pin and ground, then wire the relay contacts to switch the battery voltage directly. I feed the battery power into a boost converter to increase the voltage. Output of the boost converter goes to a new chip amp board power terminals.

The chip amp board I put in depends on how loud the owner wants to be versus how much battery life they want. Plus whether or not they are upgrading stock speakers. Louder, stock speakers, decent battery life gets a 3116 PBTL board and 24V from the boost converter. A lot louder, maybe upgrade stock speakers later, shorter battery life gets a 3255 PBTL board, 30V from the boost converter and some kind of high pass filter between the signal source and the new board to keep the stock speakers in this world for awhile. Loudest, upgraded speakers, we don't care about battery life gets a 3255 pbtl board running at recommended voltage for said load (usually between 32V and 40V, as more supply voltage is diminished return for a 12V stressed out battery and a relatively expensive boost converter, plus the stock battery charger can't keep up for long). Lower speaker impedance, lower supply voltage from boost converter.
 
Im using a 24V to 36V converter
TPA3251 is more optimized for 36V.
With the voltage increase from 24 to 36V the increase of power is a little bit over 3dB, if you push the supply voltage over 40V you get another 3dB increase for 6dB total. At around 50V you gain just a bit more control over speaker cone movement if you limit yourself to that +6dB, so slightly less likely to ruin the speaker drivers if you run them hard over longer periods of time.

Edit:
I hope your DC booster can keep up with the demand for current.
 
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