Fixing analog audio on the $2.58 HDMI-to-VGA adapter
11 hours ago
- #Hardware Modding
- #Audio Engineering
- #HDMI-to-VGA
- Bought a $2.58 HDMI-to-VGA DAC for Nintendo Switch to CRT, but audio out had severe noise and distortion issues.
- Diagnosed problems including impedance, delta-sigma DAC switching noise, and missing filtering capacitors on the PCB.
- Built a lowpass filter with resistor and capacitor; discovered DAC internal resistance ~600 ohms, making filter ineffective.
- Recalculated filter using internal resistance; optimal capacitor is ~5.1 nF for 50 kHz cutoff; used series 10 nF caps as bodge.
- Identified stereo channel swap; corrected by cutting traces and crossing audio lines with magnet wire.
- Added heatsink with thermal tape to address chip overheating; fixed video signal issues from loose cables.
- Explored second-order filter designs (e.g., Sallen-Key) but deemed too complex; other HDMI dongles also have similar flaws.
- Concluded that cheap DACs often have reversed stereo, missing capacitors, and poor design; modding is needed for usable audio.