100-yuan DIY Qualcomm 3084 Bluetooth Headphone Amplifier supports USB decoding, APTHD, LADC, 4.4 balanced interface

To let classic AKG headphones continue to be useful, I DIYed an amplifier that supports current mainstream codecs. It can connect to a computer or mobile phone for USB decoding, up to 24-bit, 96kHz, supporting aptx, aptxll, aptxad, aptxhd, and ladc. It offers good value for money. I encountered many challenges during assembly and design, so I'm sharing it first

1: Buy a ready-made 3084 Bluetooth board from Taobao. If you need a balanced interface, do not buy a single-ended one

2: When buying a lithium battery charging board, try to buy a 4-pin Type-C, as the data cable is easier to solder. I bought a 16-pin Type-C, which was too fine to solder, so I had to buy an adapter board

3: The battery should not exceed the size I bought, otherwise my box will not fit it

4: You will need very thin wires for soldering, as there is a lot of soldering. Try to buy thin wires like 24AWG or 26AWG, with an outer diameter less than 0.8mm for ease

5: Try to buy a three-position 6-pin switch. I accidentally bought a two-position 6-pin one, which means I lost the function of built-in battery power + USB decoding. I don't use my phone much, so it's fine

6: The total cost is less than 100 yuan

Here are some raw material pictures for reference, mainly for dimensions

Decoder board, the most expensive component

A pile of scattered accessories

This supports many formats and functions (but does not support copyright protection protocols, so it cannot connect to Epson projectors), but assembly is also relatively troublesome, with many wires to solder. I also made a mini amplifier that supports aptx, can connect to projectors, and the sound quality is actually decent. https://makerworld.com.cn/models/1467173, for reference. Here are two pictures showing the size difference between the two amplifiers