Analog to digital (DAC) - ZFEbHVUE/Batocera-CRT-Script GitHub Wiki

🔌 What is a DAC?

A DAC (Digital-to-Analog Converter) is a device that converts digital video signals (such as those from DisplayPort) into analog signals suitable for CRT displays. These are often used to connect modern GPUs that no longer feature native analog outputs to CRTs via VGA, SCART, component, RGBS et cetera.

One commonly recommended DAC is the CableDeconn DP to VGA adapter, known to work reliably with AMD GPUs and APUs.

🧠 Recommended DACs for CRT Output

This page documents known good-quality DisplayPort to VGA DACs suitable for CRT usage with Batocera.

🟢 DisplayPort to VGA DAC – CableDeconn (RTD2168/2166)

One of the most reliable DACs for CRT use is the CableDeconn DisplayPort to VGA adapter, which uses the Realtek RTD2168/2166 chip — originally an audio DAC repurposed for video.

✅ Key Features

  • Realtek RTD2168/2166-based: Provides clean, lag-free VGA output
  • Bit-perfect output: The video signal is passed through without processing
  • Zero input lag: No frame buffering or upscaling
  • Dot clock unlocked: Works with low resolutions (e.g., 240p)
  • DisplayPort only: Must be connected to a DisplayPort output — not HDMI
  • Compatible with AMD APUs/dGPUs: Works with supported modern AMD devices
  • Triple 8-bit DAC (24-bit color): Supports pixel clocks from as low as ~8 MHz up to 210 MHz
  • Fully supports 15 kHz CRT timings: Accurate sync, correct IRE levels, and analog fidelity confirmed by datasheet

    📄 RTD2166 datasheet confirms proper analog behavior and low-frequency timing support

⚠️ Note: Resolution switching is slightly slower than native VGA or DVI-I analog output.

❓ When to Use (or NOT Use) This DAC

This DAC is only intended for use with supported AMD systems that lack native analog outputs.

✅ Use this DAC if:

  • You are using a supported AMD APU or dGPU with DisplayPort output
  • Your hardware is listed here:
    ➡️ Supported dGPUs & APUs

❌ Do NOT use this DAC if:

  • ❌ You are using NVIDIA GPUs (including Maxwell 1.0/2.0) — analog output via DisplayPort is not supported in Linux ➡️ Supported NVIDIA Maxwell Cards (Proprietary Driver)
  • ❌ You are using an unsupported AMD GPU or only have HDMI outputs
  • ❌ You assume passive DisplayPort-to-VGA adapters will work with Nvidia — they won't

For more background, see:
➡️ Analog to Digital (DAC)

❌ Unsupported CableDeconn Models

Not all CableDeconn DACs are compatible with CRT output. The following models should be avoided:

❌ CableDeconn DP to VGA with 3.5mm Audio Out

This version adds an audio DAC internally, which interferes with proper analog video output.

❌ CableDeconn 4K DP to VGA

This model uses a different chipset optimized for high-resolution displays. It does not support low dot clocks (e.g., 240p) required for CRT output.

📌 If in doubt, only buy the known good RTD2166/2168 version — ideally the non-4K, audio-less model shown earlier in this guide.

🛠️ Fixing the Flimsy VGA Connection on This DAC

Some CableDeconn DACs have a loose VGA port. To secure the connection, you'll need:

  • VGA Gender Changer (Male to Female)
    DB9/DB15 MINI Gender

  • 4-40 Hex Screws (10mm or 12mm)
    4-40 Hex Screw

🔧 Recommendation: Use 10mm screws to avoid bottoming out the threads.
12mm is the absolute maximum.

DP2VGA with DB9/DB15 MINI Gender Changer

📌 For more CRT hardware recommendations, visit the full wiki index:
➡️ Batocera-CRT-Script Wiki