Fixing Analog Audio on a $2.58 HDMI-to-VGA Adapter
Fixing analog audio on the $2.58 HDMI-to-VGA adapter
I bought a cheap HDMI-to-VGA adapter to connect my Nintendo Switch to a CRT, but the audio output was filled with terrible noise. After diagnosing ground loops and ultrasonic interference from the delta-sigma DAC, I spent days prototyping filters and reworking the PCB. By identifying the NX3303X chip and modifying the hardware, I finally achieved clean audio from this budget device.
I will never buy a new Nintendo console after they sued Switch emulator developers, abusing their corporate legal budget to threaten independent developers with personal ruin over legally protected activity to pad their corporate coffers.
- BizarroLand
I love it when people go so far into the weeds to solve a problem on their own and then document the process for everyone.
I learned a lot from this writeup, and really enjoyed the read even though I know I would have made it about 10% of the way myself and chickened out and just bought a different product in hopes it would solve the problem.
- andrewstuart
>> A photo revealed the chip was a NX3303X; I could not find any datasheets
Not much information out there but these are similar chips, possibly it’s a clone?
Capstone CS5213 datasheet:
https://file.elecfans.com/web2/M00/2B/BD/pYYBAGHVUbyARd_-AAU...
And also the AlgolTek AG6200 / AG6201 Series, datasheet:
https://assets.yoreparo.com/attachments/28SGHqLW2Z2MfSzEBJB4...
- intralogic
That a person who seemingly is a EE will go on a deep dive like this just to figure out how to do it themselves (rather than just buy something that will work) just warms my heart about the human spirit. It makes me smile and realize that I do this myself, just in the domain of computer based devices and programming. More power to you sir, and I hope you have fun in your quest.
- Kirby64
> Annoyingly the input pins had a constant DC offset of over 2 volts, which went away when shorted to ground but reappeared moments after I removed the short.
Mic inputs on audio codecs always have DC bias, because they are DC biasing the microphone inputs so that signals can pass. By default, you would expect ~2-2.7V of DC bias on each microphone channel. This is typically connected through a high impedance (~1kOhm) source impedance. The actual impedance of the input should be extremely high resistance, though, typically in excess of 50kOhm.
The proper way to connect this would have been to a line-in jack on your motherboard. There should be no DC bias on those jacks. Or use an audio input that is 'retaskable' to select the line-in function instead of the mic-in function.
> This large of capacitance is not easily available as C0G. The usual X7R MLCC capacitors are piezoelectric and will change voltage when bumped, which can add interference to audio. Electrolytic caps are an option, but will not fit well on pads meant for 0402 ceramics.
C0Gs are not needed for passing something like this. X5R/X7Rs are commonly what is used for DC blocking capacitors in ADC/DAC solutions and you can still keep extremely good audio performance even with the theoretical microphonic problems for Type 2 dielectric capacitors.
> If we wanted to improve audio filtering, we could design a replacement PCB (four-layer for impedance matching and signal integrity?) with footprints and traces to install […]
- 0xWTF
The weird edge cases that live around connectors never cease to amaze. I recall one, I think it was also HDMI (maybe displayport or VGA), that showed there's a very low resolution digital graphic or text signal and some connectors even have a screen embedded in them.