eARC and 4K60 Over One CAT6A Run: The EXT-HDBT3ARC-TX HDBaseT 3.0 Transmitter

The problem

Audio in a long AV run has always travelled the wrong way. Video goes out from the rack to a projector or a display on the far wall, and then the room's sound has to come back the other way — from the display's streaming apps or its tuner to the soundbar, the AV receiver or the DSP sitting back at the rack. Traditionally that meant a second cable pulled in the opposite direction, or an audio extractor and a converter bolted on at the far end, or simply giving up and letting the display's own speakers carry the room.

eARC changed what a display can send back, but only over HDMI, and only as far as an HDMI cable reaches. In a boardroom with the rack in a closet, a lecture hall with a ceiling projector, or a sports bar with the amplifier behind the counter, that is nowhere near far enough.

What the transmitter does

The EXT-HDBT3ARC-TX is an HDBaseT 3.0 transmitter that carries uncompressed 4K@60Hz 4:4:4 video up to 100m (328ft) over a single CAT6A/7 cable, and carries eARC or ARC audio back down the same cable in the other direction. It is HDMI 2.0b and HDCP 2.2 compliant, and passes HDR10, HDR10+, Dolby Vision and HLG through untouched. The HDBaseT link runs 16Gbps on the main path with a separate 2Gbps return path, which is what makes room for audio coming back while 4K60 is still going out.

What returns is not a downmix. The eARC path carries lossless formats — Dolby TrueHD and DTS-HD Master Audio, along with Dolby Digital and DSD — from the display back to the transmitter, where it can leave by three different doors: the transmitter's HDMI input port, its HDMI output running in audio-only mode, or its SPDIF optical output. There is also a 3.5mm analog L/R connection for embedding audio into the link or de-embedding it at the rack.

Six routing scenes cover the combinations installers actually meet, and they are chosen on the front panel rather than in software. A SELECT button switches between ARC and SPDIF modes; separate switches set the HDMI output to loop out or audio only, set the USB role to host or device, and control L/R embedding. LEDs on the front show link state, whether video is encrypted, and which audio mode is running, so a technician standing at the rack can see what the box is doing without a laptop.

What else rides on the cable

The same CAT6A run carries more than video and returning audio:

• USB 2.0 at up to 350Mbps, with a configurable host or device role. One USB Type B host port connects to a PC, and two USB Type A ports take a keyboard, mouse or storage — enough for KVM control, a room camera or a touch panel.
• Gigabit Ethernet, so a smart display, a media player or a control processor at the far end gets network without its own drop. The LAN indicator shows green at gigabit and yellow at 100M.
• Bi-directional IR and RS-232 at up to 921,600 bps, for controlling whatever sits at either end.
• Bi-directional 24V PoC. Power the transmitter or the receiver, and the other end takes power over the cable. Only one supply has to be installed, which matters when the far end is a projector mount or a ceiling.

Where it fits

Boardrooms with the rack out of the room

Video reaches the display, eARC brings the room audio back to an AV receiver or DSP in the closet, and USB carries the camera and the touch panel. One cable pull, and the audio path does not depend on the display's internal speakers.

Lecture halls and auditoriums

A ceiling projector at distance needs no local power when PoC feeds it from the rack end, and RS-232 over the same link handles lamp or laser control and input selection from the control system.

Bars, restaurants and waiting areas

Screens run their own apps and tuners, and their audio has to reach an amplifier that is never in the same room. The SPDIF output at the transmitter hands that returning audio straight to the amplifier without an extractor in the chain.

Rooms that need KVM as well as video

With the USB switch in host mode, a PC in the rack drives a keyboard and mouse at the display end, which suits training rooms, control positions and clinical workstations where the computer must stay locked away.

Feeding a projector or display that already has HDBaseT

Many professional projectors and some commercial displays have an HDBaseT input built in, and the obvious question is whether this transmitter can drive one directly, with no receiver at the far end. HDBaseT is backward compatible by design — the HDBaseT Alliance says any two HDBaseT devices "will work at their highest common feature set" — so a link will generally come up. What matters is what that common feature set turns out to be, because it is set by the receiving end, not by the transmitter.

Reading the published specifications for the projectors on the market today, three things are worth knowing before you order a transmitter on its own:

The far end usually sets a lower ceiling than the transmitter

Most built-in projector inputs are an earlier generation of HDBaseT and accept 4K at 30Hz, or 4K60 with 4:2:0 colour, or in a good number of cases 1080p only. Several makers publish a pixel-clock figure for the HDBaseT input around 297–300 MHz, which is an older link rate and cannot carry 4K60 4:4:4 whatever is sending to it. Others mark 4K50 and 4K60 in their signal tables as HDMI-only, or state a shorter maximum distance for 4K than for 1080p — 50 to 70 metres is common, against 100 metres for 1080p. Read the projector's signal table for the HDBaseT input specifically, not the HDMI table beside it, and check the HDCP version on that input too: a few current models are HDCP 1.4 only, which protected sources will refuse.

Only video, audio and control cross over

Projector HDBaseT inputs carry video, control and 100Mb Ethernet. USB is not part of any projector implementation we found, and no projector takes an eARC or ARC return, because projectors have no audio to send back. So the USB 2.0, Gigabit Ethernet and audio-return features of this transmitter are for rooms where the far end is a matching receiver, a display with a soundbar, or an AV receiver — not for a projector link. Some models also share one RJ45 between HDBaseT and LAN, and at least one maker warns that plugging a transmitter into the wrong jack can cause a malfunction.

Power over the cable needs care

This transmitter applies bi-directional 24V PoC, which is how it powers a KanexPro receiver at the far end from one supply. Projectors are mains-powered and do not take power over the HDBaseT cable. Industry installation guidance is to check that a device applying power over category cable is matched to what the far end expects, so talk to us before connecting this transmitter to a projector's HDBaseT input, and tell us the projector model.

The configuration KanexPro documents and tests is this transmitter with its matching HDBaseT 3.0 receiver, available together as the EXT-HDBT3ARC-100M kit. That pairing is where the full feature set — 4K60 4:4:4, the audio return, USB and Gigabit Ethernet — is actually delivered end to end.

What the far end accepts: projectors and displays with HDBaseT built in

Every figure below is what the maker's own documentation states its HDBaseT input accepts. Read it as the ceiling that end of the link sets, not as a compatibility claim, and check the model's own signal table before you order. Note how often the HDBaseT input is slower than the same product's HDMI input.

Projectors that accept 4K60 over HDBaseT

• Christie 4K10-HS and 4K7-HS with the HDBaseT 4K input card: 3840×2160 at 60Hz, 4:4:4 8-bit, HDCP 2.2, 100m on Cat6/7. The best-documented input of any projector we read.
• Optoma ZK1000, ZK1120 and ZK1320: the HDBaseT timing table matches the HDMI table, including DCI 4K at 60Hz. ZK810T, ZK708T and ZK420UST also take 4K60; Optoma calls these HDBaseT 3.0.
• Sharp/NEC XP-X171Q and XP-X141Q: certified at 4K60 4:4:4, 100m.
• Vivitek DU6098Z, DU6198Z, DU6298Z and the DU7099Z+ family: a dedicated HDBaseT column showing 3840×2160 at 60Hz.
• Barco G100 series: 3840×2160 at 60Hz, 8-bit; DCI 4K stops at 30Hz.
• Epson Pro L1490U through L1755UNL: 4K signals are allowed on HDMI and HDBaseT. On the earlier Pro L1100U to L1505U generation the same table marks 4K as HDMI only.

Projectors whose HDBaseT input stops below 4K60

• Panasonic DIGITAL LINK (PT-RQ35K2, RZ34K2, MZ882, RZ990 and the rest): 4K at 50 and 60Hz is 4:2:0 only, up to 50m; 1080p reaches 100m, or 150m in long-reach mode.
• Sharp/NEC PA1705UL, PA1004UL and PA803U: 4K at 24 to 30Hz, and 70m rather than 100m at 4K. PX2201UL and PV800UL are HDCP 1.4 only, and the PX2201UL takes no 4K over the link at all.
• Sony VPL-FHZ85, FHZ80, PHZ61 and PHZ51: 4K at 24 to 30Hz over HDBaseT, while the HDMI inputs on the same projector take 4K50 and 4K60.
• Maxell MP-WU8801W, WU8701W and WU8101W: 4K50 and 4K60 over HDBaseT are 4:2:0 only. MP-WU5603 and its family stop at 4K30.
• Digital Projection E-Vision and TITAN: 4K at 24 to 30Hz is 4:2:2 only, 4K50 and 4K60 are 4:2:0, and the Satellite TITAN is HDBaseT up to 30Hz.
• Christie GS, HS and Inspire series: 4K at 24 to 30Hz, 8-bit; the Inspire carries HD only over HDBaseT even on the 4K model.
• BenQ LK936ST, LK935 and LK954ST: the manual states the HDBaseT port takes up to 1080/60p and does not support LAN control, and its 4K line is 4:2:0 at half the distance. LU950, LU951, LU9715 and LU9915 are 1080p over the link.
• ViewSonic LS920WU and LS921WU: 1080p only. LS950WU, LS951WU and LS960WU: 4K at 24 to 30Hz.
• Barco F80 series: HDBaseT 1.0, 4096×2160 at 30Hz, with no Ethernet, IR, RS-232 or power over the link. G62: 4K30.

Displays and signage

• Panasonic SQ1 signage and VF2 video wall panels carry DIGITAL LINK built in: 4K30 4:4:4 or 4K60 4:2:0, 70m at 4K, with 100Mb Ethernet and RS-232. Panasonic's own DIGITAL LINK transmitter boxes are discontinued and were never 4K.
• Sharp/NEC displays with an Intel SDM slot take the SDM HDBaseT receiver module: 4K60 4:4:4 with HDCP 2.2, at 70m for that rate, on Cat6a or Cat7. Host displays include the M, MA, ME and P series.
• Hisense 55OP90FE outdoor display: HDBaseT input built in, 4K at 24 to 30Hz in YUV, where its HDMI inputs take 4K60.
• Samsung OHB and OHDX, and LG XE4F outdoor displays keep an HDBaseT input, but both are 1080p panels.
• Crestron TS-1542-C touch screen: 4K30, 70m.
• Most current indoor signage from Samsung, LG, BenQ, ViewSonic, Christie, Barco, Planar, Philips, Sony and TCL has no HDBaseT input at all — it is HDMI and DisplayPort, sometimes with a slot module as the only route.

Three things no projector or display HDBaseT input does: carry USB, carry Gigabit Ethernet (100Mb is the norm), or return audio. Audio return needs a receiver at the far end to collect it from the display's HDMI eARC port, which is why the EXT-HDBT3ARC-100M kit is where this transmitter's eARC, USB and Gigabit Ethernet are delivered end to end.

In the box

One EXT-HDBT3ARC-TX transmitter, an IR blaster cable and an IR receiver cable (1.5m each), two 3-pin 3.81mm Phoenix connectors, and four mounting ears with screws. Power is DC 24V/1A, or over the cable by PoC.

Specifications at a glance

• HDMI 2.0b, HDCP 2.2, HDBaseT 3.0
• Up to 4K@60Hz 4:4:4, HDR10, HDR10+, Dolby Vision, HLG
• 16Gbps main link, 2Gbps return link
• eARC/ARC return to HDMI IN, HDMI OUT (audio only) and SPDIF OUT; 3.5mm L/R embed and de-embed
• USB 2.0 up to 350Mbps, host or device; 1× USB Type B, 2× USB Type A
• Gigabit Ethernet, bi-directional IR, RS-232 up to 921,600 bps
• Up to 100m (328ft) over CAT6A/7
• Bi-directional 24V PoC

Full details and documents are on the EXT-HDBT3ARC-TX product page.