Mod input sensitivity TPA3255

[DiegoAlm]

Hello everyone, this is my first post on the forum, sorry if it's not in the right subforum.

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 and a 36V converter 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 or the resistors? The specific amplifier is this
https://a.aliexpress.com/_mOGPHeg

 

[NTK]

Welcome to ASR!

The easy option IMHO is to add a headphone amplifier with a gain of at least 2 between your DSP board and speaker amp. If you want to DIY, you can build yourself a battery powered CMoy, which should be relatively easy. The design as given by Chu Moy (RIP) had a gain of 11, so you may want to adjust the resistor values to give your desired gain.

A Pocket Headphone Amplifier | HeadWize

If you are more adventurous, not afraid of mucking with tiny surface mount components, and want to do surgery to your TPA amp, you will need to figure out the input buffer schematic. Absent of that here, I am using the TI TPA3255 eval board schematic as example.

The TPA3255 uses differential inputs, and thus there are 2 op-amps for the input buffer per channel. Since the manufacturers usually use dual packaged op-amps, that means 1 chip per channel.

In the TI TPA3255EVM, the buffer is inverting and the gain is given by -R8/R7 and -R41/R42 (the two sets needs to be the same as each other). In the TI EVM design, the buffer is unity gain and therefore R7 = R8 = R41 = R42. [Edit] You may double R8 and R41 or reduce R7 and R42 by half (which will reduce the input impedance of the amp to 5 kohm) to double the gain of the buffer.

SLOU441 EVM User's guide | TI.com

TPA3255EVM

www.ti.com

 

[Roland68]

Welcome to ASR!

The easy option IMHO is to add a headphone amplifier with a gain of at least 2 between your DSP board and speaker amp. If you want to DIY, you can build yourself a battery powered CMoy, which should be relatively easy. The design as given by Chu Moy (RIP) had a gain of 11, so you may want to adjust the resistor values to give your desired gain.

A Pocket Headphone Amplifier | HeadWize

If you are more adventurous, not afraid of mucking with tiny surface mount components, and want to do surgery to your TPA amp, you will need to figure out the input buffer schematic. Absent of that here, I am using the TI TPA3255 eval board schematic as example.

The TPA3255 uses differential inputs, and thus there are 2 op-amps for the input buffer per channel. Since the manufacturers usually use dual packaged op-amps, that means 1 chip per channel.

In the TI TPA3255EVM, the buffer is inverting and the gain is given by -R8/R7 and -R41/R42 (the two sets needs to be the same as each other). In the TI EVM design, the buffer is unity gain and therefore R7 = R8 = R41 = R42. [Edit] You may double R8 and R41 or reduce R7 and R42 by half (which will reduce the input impedance of the amp to 5 kohm) to double the gain of the buffer.
View attachment 297584

SLOU441 EVM User's guide | TI.com

TPA3255EVM

www.ti.com

With the SE input, you must not change R41/R42 under any circumstances, as these belong to the subsequent inverted OPAmp.

@DiegoAlm
You may only raise R8/R7. Just set the value to 20k like the AIYIMA A07