This is a continuation of a DIY Mini (or micro) headphone amplifier. I have already talked about it in the first part and even made a working prototype. But the protopine was big in size, so I have decided to order a PCB and make it as small as possible.
Other post parts
- DIY portable headphone amplifier based on an INA1620 chip and TPS65135 (Part 1)
- DIY Micro PCB Headphone Amplifier (Part 2) (This page)
- Micro USB-C to 3.5mm Adapter and Headphone Amplifier (Part 3)
- DIY Micro USB-C to 3.5mm Adapter and Headphone Amplifier (Part 4)
The PCBs made by PCBWay
Yet again I have got the boards from PCBWay which also sponsored the boards which are showed in this post. Nonetheless, their PCB manufacturing pricing is good and they manufacture the board quickly and deliver them safely.

If you want to get more information about how to order the boards by yourself, I have already covered it in one of my blog post here.

The Boards
These boards are 18 mm x 6 mm in size. Their thickness is 0.8 mm. So, as the this post’s title suggests – the boards are tiny!

On the board there are place for two main circuits. The first one is operational amplifier based on INA1620. Its gain is fixed and set to 2. As the previous testing shows, gain of 2 is optimal for both worlds – low and high impedance headphones. Well, it might be a bit too much for low impedance ones – the distortion can be heard, but you can always just turn down the volume a bit :).

The second circuit, which is populated on the board, is power delivery. It is based on a TPS65135 IC. Its main purpose to make dual voltage for the op-amp from a single voltage (5V) supply.
As you can see in a photo below, the electronics parts goes on both PCB sides:

Again, the boards are so tiny that there were not enough space on the front side to fit component markings. Note, that as the boards are so small, the PCBs in the photo above might look worse than they are in reality – all markings are perfectly visible and there are no visible quality issues.
Finally, the main idea of such small PCB was to make an adaptor-like USB-C device. On one end it will have a USB-C DAC which will then connect to this amplifier circuit and from it the signal will go to a 3.5mm audio jack.

Further Steps
Next step is to order some components which I still don’t have, somehow solder the PCB and test how it works. Final step will include manufacturing some kind of enclosure for this device.