RetroRGB Tests RGB-Pi 2 and Reflex Prism Against Budget HDMI DAC Options

Getting clean 240p or 480i out of modern HDMI hardware without added lag, color drift, or constant fiddling is harder than it looks. RetroRGB's Bob tested two new HDMI-to-analog DAC solutions, the RGB-Pi 2 and the Reflex Prism, against a budget $8 VGA DAC and an HD15-to-SCART adapter to find out which converter actually deserves a place in your signal chain. The results started promising for both devices, then took a sharp turn: a follow-up correction revealed the RGB-Pi 2 has a fundamental hardware defect that currently makes it impossible to recommend.

What Was Tested and Why It Matters

The core problem this comparison addresses is one every MiSTer FPGA owner, Amiga user, or console modder eventually hits: your source outputs HDMI, but your CRT, PVM, or capture card wants analog RGB, component, or S-Video. A DAC is the bridge between those two worlds, and the quality of that bridge directly determines your black levels, color accuracy, sync stability, and whether you end up post-processing footage for hours. Bob used the $8 VGA DAC, a common budget recommendation, and the HD15-to-SCART adapter as baselines, then put both the RGB-Pi 2 and Reflex Prism through the same signal chain to see where each one earns its price.

The Reflex Prism: Full-Featured and Genuinely Solid

The Reflex Prism, produced by MiSTer Addons, converts HDMI to analog with zero lag, outputting simultaneously through an HD15 (VGA) port and a Sega-Saturn-style Mini-DIN-10 connector. The HD15 port switches between RGBHV and YPbPr via a slide switch on the unit, while the Mini-DIN-10 carries both RGBs and S-Video at the same time, giving you immediate flexibility for CRT monitors, PVMs, and consumer televisions without rewiring. Units shipping in 2026 include an onboard composite sync combination circuit, which means common sync compatibility headaches are handled in hardware.

Bob's voltage measurements came back clean across the board: RGB output levels were described as "all identical and all great," SCART sync voltage was well below the maximum safe threshold, and VGA sync was right where it should be. For most setups, the Prism is genuinely plug-and-play. Connect it, leave every switch at default, and it works.

The one area that required extra attention was MiSTer FPGA Direct Video mode. To use the Prism with MiSTer in Direct Video, you need to either open the unit and toggle internal switches, or edit the MiSTer.ini file. Bob's recommended approach is the .ini edit, which is non-destructive and reversible. Inside the Prism's shell, there is an NTSC/PAL jumper for the S-Video output, a power jumper, a hidden switch controlling sync from the HD15 port, and DIP switches for sync combining modes and a passthrough mode. Bob's only real complaint about the hardware was that accessing these required removing the top panel, which was "kind of a pain." For most users, those switches will never need to be touched after initial setup, but the ergonomics of internal configuration are worth knowing before you buy.

A few compatibility notes worth checking before purchase:

• The Prism expects RGB-formatted HDMI input and outputs at the same resolution it receives, so it does not downscale.
• Analogue Ltd. consoles are not compatible because they require a specific EDID signature the Prism does not provide.
• The minimum supported HDMI input resolution is 480p, meaning it cannot be used to pipe a 240p/15kHz signal from a Switch, PS5, or Steam Deck to a CRT. It can, however, connect those devices to a PC CRT monitor.
• Composite video output is not officially supported and may produce dot crawl.

The RGB-Pi 2: Promising Hardware, Serious Problems

The RGB-Pi 2 was initially appealing on paper. It is a compact 24-bit HDMI DAC that, when paired with the RePlayOS frontend for Raspberry Pi, adds genuinely useful features: an analog sync output through a 3.5mm port for light gun support, and the ability to toggle between AND and XOR sync combining to resolve compatibility issues with demanding displays. It is physically even smaller than the $8 VGA DAC used as a baseline in the tests.

Bob's initial livestream on March 27 gave the device a positive early look, but a follow-up correction issued on March 31 changed the picture significantly. After verifying results with multiple signal sources and cross-checking against two other DACs, Bob found that the RGB-Pi 2's green channel outputs over a hundred millivolts below red and blue. That voltage gap means the colors will never balance correctly, regardless of any software or display-side correction applied. A viewer watching the second livestream independently confirmed the same behavior on their own unit, ruling out a single defective sample.

Bob's summary of the current situation was direct: "At the moment, I wouldn't recommend this at all." The apology on the RetroRGB homepage was public and specific, aimed at anyone who purchased based on the Part 1 stream. That kind of transparency is exactly what makes Bob's testing trustworthy, but it also means the RGB-Pi 2 is a device to watch rather than buy right now. If the hardware issues are resolved in a future revision, the feature set and compact size would make it a strong recommendation for anyone wanting a basic HDMI-to-RGB SCART solution.

The $8 VGA DAC: Useful in a Narrow Lane

The budget VGA DAC used as a baseline performed adequately, but within a very constrained use case. Inexpensive VGA converters can handle 480p and above reasonably well, but they consistently lack audio support, do not pass 15kHz signals, and many drop sync when the source switches between 240p and 480i. For a modern PC CRT or an HDMI source that stays locked at 480p or higher, a cheap VGA DAC can get the job done without spending more. For anything retro-oriented, meaning CRT TVs, PVMs, or SCART-connected monitors running 15kHz content, a budget VGA DAC is not a viable solution and the HD15-to-SCART adapter alone does not fix those underlying limitations.

Picking the Right Path for Your Setup

The practical decision comes down to what you are connecting and why:

• For MiSTer, Amiga, or any HDMI source going to a CRT or PVM with full 15kHz support, proper sync levels, and S-Video or component output: the Reflex Prism is the current clear recommendation.
• For capture workflows or preservation work where color accuracy and voltage consistency matter across sessions: again, the Reflex Prism earns its price by eliminating the variables that budget converters introduce.
• For PC CRT owners running 480p and above who do not need audio or 15kHz: a quality VGA DAC remains a cost-effective bridge.
• For the RGB-Pi 2: hold off until a revised version addresses the green channel voltage imbalance.

The broader lesson from Bob's testing is one the retro-video community keeps relearning: the analog signal chain has no mercy for cut corners. A hundred-millivolt difference in one color channel is invisible on a spec sheet and immediately visible on a CRT, and no amount of software correction fully compensates for it. When the hardware is right, like the Reflex Prism's verified voltage output, the rest of the chain becomes dramatically easier to manage.