StarTech ST122HD4KU 2-Port 4K HDMI Splitter with 7.1 Surround Audio

Overview

The StarTech ST122HD4KU is a 2-port HDMI splitter designed to mirror a single 4K source to two displays simultaneously — both video and audio, without compromise. Where most budget splitters drop audio handling entirely or cap out at 1080p, the ST122HD4KU passes 4K at 30Hz alongside full 7.1 surround sound, making it the right tool for boardrooms, digital signage pairs, control room workstations, and AV distribution setups where audio continuity matters as much as image fidelity. The unit measures just 24.4 × 2.0 × 0.7 inches and weighs 2.5 oz, so it disappears behind a rack shelf, under a desk, or inside a display enclosure without taking up meaningful space.

Key Features

• 4K @ 30Hz output to both ports simultaneously: The ST122HD4KU drives both connected displays at up to 3840×2160 resolution — enough pixel density to render fine text, charts, and detailed video crisply on large-format commercial panels. Note that this is 30Hz, not 60Hz — appropriate for signage, presentations, and monitoring feeds, but not ideal for high-frame-rate gaming or motion-critical video.
• 7.1 surround sound pass-through: Most 2-port splitters treat audio as an afterthought. This unit passes 7.1 channel surround audio to both outputs, which means AV installations that rely on the HDMI audio channel — conference rooms with ceiling speaker arrays, AV receivers, or soundbars — stay fully functional on both screens without a separate audio distribution path.
• Multi-resolution compatibility (2560×1600 down to 1280×720): The splitter negotiates across a broad resolution stack — 3840×2160, 2560×1600, 1920×1200, 1920×1080, and 1280×720. In mixed-display environments where the two connected screens have different native resolutions, the unit will typically output at the lower common resolution. Plan for matched display pairs if you need both screens at native 4K.
• Universal AC input (100–240V, 0.4A): The included power supply accepts any global mains voltage, so the same unit ships to international installations, temporary deployments abroad, or multi-site enterprise rollouts without requiring a region-specific adapter or power brick swap.
• 10W total power consumption: At 10 watts operational draw, the ST122HD4KU places almost no load on a UPS or PDU. On a standard 1500VA UPS, you could run dozens of these alongside primary equipment without affecting runtime calculations in any meaningful way.
• 5V DC / 2A regulated output: The external power supply delivers a clean 5VDC at 2A to the splitter's internal circuitry — a stable supply that reduces the risk of sync dropouts or display handshake failures that plague passively-powered HDMI splitters.
• Operating temperature 5°C to 70°C (41°F to 158°F): The thermal envelope is wider than most consumer-grade AV equipment, which matters in above-ceiling, behind-panel, or equipment-room installations where ambient temperatures climb above comfortable office range. Avoid deployments in unventilated outdoor enclosures where ambient can exceed 70°C.
• Compact form factor (24.4 × 2.0 × 0.7 in, 2.5 oz): The thin, flat profile is deliberate — it fits into narrow cable management trays, attaches behind flat-panel mounts, or drops into a shallow rack accessory shelf. The 2.5 oz weight means no secondary mounting hardware is needed in most installs.
• 2-year manufacturer warranty: StarTech's 2-year warranty on the ST122HD4KU provides a practical coverage window for commercial installations — long enough to outlast most AV project warranty obligations to end clients.

Integration and Compatibility

The ST122HD4KU connects to any HDMI-equipped source — laptops, media players, NVRs with HDMI monitor outputs, cable boxes, or dedicated video wall controllers. Because the splitter mirrors rather than extends, both downstream displays receive identical content at identical resolution and audio depth. For installations pairing this with a video surveillance system that outputs a live view to HDMI, the splitter allows simultaneous monitoring on a local operator screen and a secondary display in an adjacent area without a second video output on the recorder. If your source device requires HDCP compliance on the downstream displays, both connected monitors must support HDCP for content to pass — a common gotcha in digital signage or hospitality AV deployments using DRM-protected content streams. For broader HDMI distribution accessories and cables, verify that your HDMI cable runs to each display are rated for 4K signal integrity, particularly on runs exceeding 15 feet.

Frequently Asked Questions

Q: Does the ST122HD4KU support 4K at 60Hz?

A: No. The ST122HD4KU supports a maximum resolution of 4K (3840×2160) at 30Hz. If your application requires 4K@60Hz — such as high-frame-rate video playback or gaming — this unit is not the correct choice. For standard digital signage, surveillance monitoring, and presentation mirroring, 4K@30Hz is sufficient.

Q: Can the two outputs display different content?

A: No. This is a splitter, not a matrix switch. Both HDMI outputs mirror the single input identically — same resolution, same audio, same content. For independent content on each screen, you would need a separate HDMI matrix or multi-output graphics solution.

Q: Does the ST122HD4KU pass audio to both outputs?

A: Yes. The unit passes up to 7.1 surround sound over HDMI to both connected displays simultaneously. Audio is not stripped or downmixed — both outputs receive the full audio channel embedded in the HDMI signal.

Q: What is the warranty on the ST122HD4KU?

A: StarTech provides a 2-year manufacturer warranty on the ST122HD4KU.

Q: Will this work with displays of different resolutions?

A: The splitter supports multiple resolutions — 3840×2160, 2560×1600, 1920×1200, 1920×1080, and 1280×720 — but will typically negotiate to the lowest common resolution when the two connected displays have different native resolutions. For best results, use matched display pairs.

Q: Does the ST122HD4KU require external power?

A: Yes. The unit requires an external power supply (included) that accepts 100–240V AC input and provides 5V DC at 2A to the splitter. It is not bus-powered from the HDMI source.

Karl Wilson

The detail that stands out to me on the ST122HD4KU is the 7.1 surround audio pass-through on a 2-port splitter at this form factor — 24.4 inches long, 2.0 inches wide, 0.7 inches tall, 2.5 oz. Most installers don't think twice about audio when speccing a splitter, then spend a service call troubleshooting why the AV receiver on display two is getting stripped audio or no signal at all. This unit eliminates that scenario entirely by embedding the full audio channel in both outputs.

Technical Highlights:

• 4K @ 30Hz dual output: Both ports simultaneously deliver up to 3840×2160 — enough for large-format commercial signage panels and operator monitoring displays without a secondary video card or encoder in the chain.
• Universal 100–240V AC input: The included power supply handles any global mains voltage at 0.4A draw, which simplifies multi-region and international deployments where a dedicated region-specific adapter would otherwise be required.
• 10W operational consumption: At 10 watts total, this adds negligible load to a PDU or UPS — relevant in control rooms and server closets where power budgets are tracked per circuit.

Deployment Considerations:

• The 5°C to 70°C operating range supports above-ceiling and equipment-room installs, but verify ambient temperatures in enclosed AV bays — passive enclosures with multiple active components can push past 70°C without active cooling.
• The ST122HD4KU caps at 4K@30Hz — confirm your source and both displays align on this refresh rate before committing to this unit in any motion-heavy or frame-rate-sensitive application.

This unit fits well in dual-screen boardroom presentation setups, NVR monitor duplication for adjacent security stations, and hospitality AV closets where a single media player needs to feed two display zones with full audio intact.