CYD Mods for better Audio

[ideal54]

In the read.me file is a section on modifications describing how to improve the audio quality. I've recently bought some CYD's with two USB ports and one of the issues with them is loud distorted audio. My earlier CYDs didn't suffer from this issue so I investigated. It turns out some PCBs have the wrong resistors in the audio input circuit which allows the DAC output to overload it. The image provided in the read.me file shows one of these boards. In the CORRECT circuit R7 is 47k, R8 is 22k and R9 is 47k. These values give nice quality audio with the volume level easily controlled by the internal DAC attenuator. In boards with the wrong components, R7 is 0 Ohms, R8 is 0 Ohms and R9 is 68k which results in high level distorted audio that the DAC attenuator cannot control. Simply change these three resistors back to their original values for excellent audio.

[clach04]

Interesting. I hooked up some cheap speakers and got a not so faint background noise, possibly due to unshielded wires. I need to add this to my TODO list of things for check. Thanks for sharing 🙏

[ideal54]

I’ve attached photos of the two boards. The board with 0 ohm resistors has the incorrect values for R7, R8, R9. The other board has the correct values.