Mod a TPA3116 amp for Differential Inputs

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When prototyping a new speaker system, I recently picked up the Yuan-Jing TPA3116 amplifier at Parts-Express.  The TPA311x amplifier ICs from TI are a great series of parts which provide high efficiency amplification at a range of power levels.  The design of this board is pretty good, with film capacitors, a clean layout, and a heatsink for the TPA3116. In the design of this board the negative side of the input has been tied to ground, making it a single ended input.  I usually like to connect my amps using a differential input which typically gives more output with better noise rejection.  The following modification makes the stereo inputs 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
  • 2 – 1uF film capacitors. 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 caps.
  • Adhesive, I used hot-melt.  Superglue will also work.

Prepping the board

We need to start by removing the grounding capacitors.  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:

Grounding caps removed.
Grounding caps removed.

Add new input coupling caps

Now we need to add the new coupling capacitors for the negative side of inputs.  Bend one lead 90 degrees.  Check out the placement so you know where it is going to sit.  I placed them on the bottom of the PCB over the mounting holes.  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.  Repeat for the other cap as shown below.

 

 

New Input Caps
New Input Caps

 

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.  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.

Diff Input Wires
Diff Input Wires

The Finished Amplifier

Our completed amplifier, ready for installation

Diff input amplifier.
Diff input amplifier.

 

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

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