The CX31993 Datasheet Fix is an essential patch for anyone serious about implementing this chip outside a pre-built dongle. It’s not pretty, it’s not official, but it works. If you’ve been frustrated by the chip’s erratic behavior at 44.1 kHz or silent I²C commands, this document will feel like finding the lost manual.
Recommended for: Embedded audio developers, USB gadget tinkerers, repair technicians reverse-engineering cheap dongles.
Not for: Beginners looking for a simple “how to use” guide – you’ll still need basic I²C and USB audio knowledge.
Have you used the CX31993 datasheet fix? Share your own register discoveries in the comments. Cx31993 Datasheet Fix
Note: If you meant a different component (e.g., CX20993, CX31983, or a generic Chinese USB DAC dongle), the approach remains similar — verify pinout and power sequencing.
The official datasheet does not list I²C or HID registers for gain control. The actual gain steps (used by Windows/macOS drivers) are: The CX31993 Datasheet Fix is an essential patch
These are applied via vendor-specific USB control requests (bRequest = 0x23, wValue = register). Not user-configurable without a driver override.
After all software fixes, some CX31993 dongles are simply defective due to: Have you used the CX31993 datasheet fix
If you experience persistent hiss with low-impedance IEMs or connection drops when moving the cable, no registry tweak will help. Return the dongle and buy one from a reputable manufacturer that publishes its own application notes (the consumer-friendly version of a datasheet).
Brands with reliable CX31993 implementations:
| Symptom | Probable Cause | Fix | |---------|----------------|------| | No sound, PC detects “USB Audio” | Missing HID init command | Re-flash EEPROM with generic USB audio descriptor (use USBAudio v1.0 template) | | Static noise on headphone out | Poor ground routing | Cut digital ground plane under crystal; star-ground to USB connector shell | | Volume too low | Output stage not enabled | Pull HP_DET pin high via 100 kΩ to 3.3V (if present) | | Only left channel works | I²S data line swapped | Swap SDIN/SDOUT pins on PCB trace cut |