Mod a TPA3116 amp for Mono Mode

posted in: Mods | 3

When prototyping a new speaker system, I recently picked up the Yuan-Jing TPA3116 amplifier at Parts-Express. As mentioned in our Diff Input Mod, the TPA311x amplifier ICs from TI are a great series of parts which provide high efficiency amplification at a range of power levels. Another feature of the TPA3116 is its ability to run its outputs in parallel.  By doing so, the amplifier can drive lower impedance speakers, resulting in double the power.  eg, Instead of driving two 4 ohm speakers at 50W each, you can drive a single 2 ohm speaker at 100W.  In this mod we also configure the input as differential. Of course making these modes will void any warranty, proceed at your own risk.

Before you start

Required materials

  • A soldering iron and basic soldering skills
  • Hookup wire 26AWG
  • 1 – 1uF film capacitor. I am using Epcos B32529C105K*

*This is a 63V capacitor. For most applications this will be fine. If you are connecting to a source with a higher bias voltage then you will need to choose a capacitor accordingly.

Recommended

  • A solder puller will help for removal of the existing ground cap.
  • Adhesive, I used hot-melt. Superglue will also work.

About the Mod

To run the TPA311x amplifiers in mono mode, you must connect the left input pins directly to ground.  Once connected to ground, you then short the Left +/- output pins together, and also short the Right +/- pins together.  The right pins become the new positive output, and the left pins become the new negative output.  This output mode is also called PBTL for Parallel Bridge Tied Load.

Prepping the board

We need to start by removing the right input ground capacitor. If you have a solder puller remove the solder from the pins first. You will need to heat the pins from the bottom while pulling up on the caps. Once the solder flows they should remove easily. It helps to alternate between pins. Be careful not to lift the topside etch! Once they are removed clear the holes and your board will look like this:

 

Right input ground cap removed.
Right input ground cap removed.

Reworking the Input

  • Add a wire to the Left input pins on the bottom of the PCB, and connect them to ground.
  • Now we need to add a new coupling capacitor for the negative side of the right input.  Bend one lead 90 degrees.  Check out the placement so you know where it is going to sit.  I placed it on the bottom of the PCB over the mounting hole.  If you plan to use those mounting holes, you will need to place it in a different location.  Add a drop of adhesive to the back-side of the cap and glue it in place on the PCB.  Then solder the input lead.
Shorted left input pins,
Shorted left input pins,

Input Wires

The final step is to add input wires. Since the input connector only supports single-ended input, we will bypass it and solder input pairs to the bottom of the PCB & the new input cap. Be sure to use twisted or shielded wires for your input signals. I also put a little hot-melt to tack the wires to the PCB, this ensures that the wires will not pull against the cap & pcb.

 

 

 

MonoInputRework2

Jumper the Outputs

Make small jumper wires and short the outputs as shown in the following photo.

Output Jumpers
Output Jumpers

Add one side of your speaker wiring to each of these jumpers.

 

Outputs wired for mono
Outputs wired for mono

 

<h2>The Finished Amplifier</h2>
Our completed amplifier, ready for installation

Completed Mono Amp
Completed Mono Amp

 

If you liked this mod, you might also like our TPA3116 Diff Input Mod!

3 Responses

  1. tallnutt
    |

    Hi. Great mod, thanks. Is there a way to bridge the 2.1 version of this amp to mono mode? i.e both the stereo amp and bass amp bridged together?

    • jgmadd0x
      |

      Hey tallnutt: There is no easy way to bridge the two separate amp chips without risking damage to the ICs.

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