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We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-10-04 · 7 min read · Independent comparison
• Avantree Relay & SoundJet — biggest strength: a flight-first design that pairs two Bluetooth headphones at once from a 3.5mm AUX source, with Qualcomm aptX Adaptive audio and up to 25 hours of playtime on one charge.
• Avantree Relay & SoundJet — biggest trade-off: it is a transmitter only for AUX sources. It is not built for TVs, phones, hearing aids or instruments, and it will not pair with a phone or tablet as a source.
• SUNITEC Auracast Transmitter USB-C — biggest strength: a 2-in-1 USB-C dongle that does Classic Bluetooth and Auracast broadcast, covers aptX Adaptive and aptX HD, and can send audio to one headset or to virtually unlimited Auracast receivers at once.
• SUNITEC Auracast Transmitter USB-C — biggest trade-off: it is audio playback only with no microphone input, and the Auracast broadcast side only works with compatible Auracast or LE Audio receiving devices.
• Who each pick is for: Avantree for travelers and couples sharing one in-flight screen; SUNITEC for PC, Mac and PS5 users who want aptX HD earbuds, one-to-many sharing, or hearing-aid broadcasting.
The Relay & SoundJet R1 Bundle is built around one job: getting audio off a 3.5mm AUX jack and into Bluetooth headphones. That is exactly the situation on a plane, where the seat-back screen has a headphone port and you would rather not use the flimsy wired earbuds in the seat pocket. You plug into the AUX output, and the adapter transmits wirelessly to your headphones. The headline feature is that it pairs two Bluetooth headphones or AirPods at the same time, so two people can watch the same movie side by side without splitting a single earbud.
I recommend the Avantree for couples, travel partners, and anyone who flies often and wants a smarter wireless upgrade for in-flight entertainment. I would steer you away if you are shopping for a TV, a phone, a tablet, a hearing aid, or an instrument — this bundle is explicitly not for those, and it will not act as a receiver for your phone either. It is a niche tool, but within that niche it is focused and well matched to the task.
SUNITEC Auracast Transmitter USB-C: Who It's For
The SUNITEC BT400T is a different animal entirely. It is a USB-C dongle that plugs into a PS5, PC, MacBook, laptop, tablet or USB-C smartphone and transmits Bluetooth audio out of it. The 2-in-1 design lets you switch between Classic Bluetooth and Auracast Broadcast Mode with a single button. In Classic mode you pair one headset for private listening, with a wireless range of up to 33ft (10m). In Auracast mode you broadcast to virtually unlimited Auracast-compatible headphones, speakers and hearing aids at once, with the range stretching to about 164ft (50m).
For anyone chasing the best sound out of aptX HD earbuds, this is the more interesting device. It supports AAC, SBC, aptX, aptX Adaptive and aptX HD in Classic Bluetooth, plus LC3 for Auracast. That codec list is what makes it worth a look for gaming, movies and music, where aptX Adaptive and aptX HD help keep audio responsive and in sync. It also has dedicated sampling modes: a 24kHz setting aimed at compatible Auracast hearing aids and a 48kHz setting for Auracast headphones and speakers, switched with one button. Compatible devices can discover and join the broadcast without pairing.
It is plug-and-play — no drivers or apps — and works across iPhone 15/16/17, Android phones, tablets, iPads, laptops, desktops and PS5. Two caveats matter. First, it is playback only: no microphone input or voice chat, so on PS5 you would use the controller mic instead. Second, Auracast broadcast requires compatible Auracast or LE Audio receiving gear. I recommend the SUNITEC for gamers, PC and Mac users, and anyone who wants one-to-many audio sharing for classrooms, conferences, gyms, museums or assistive listening. Skip it if mic input is a must, or if your headphones and speakers are plain Classic Bluetooth only and you were hoping for broadcast.
• Best for in-flight entertainment with a partner → Avantree Relay & SoundJet. Two headphones at once from a 3.5mm AUX seat-back jack is its whole reason for existing.
• Best for aptX HD earbuds on a computer or console → SUNITEC Auracast Transmitter USB-C. It is the one that lists aptX HD and aptX Adaptive on the transmitter side over USB-C.
• Best for battery life away from a power outlet → Avantree Relay & SoundJet. Up to 25 hours of playtime on a single charge, versus a dongle that draws from the host device.
• Best for one-to-many sharing → SUNITEC Auracast Transmitter USB-C. Auracast broadcast reaches virtually unlimited compatible receivers with up to 164ft (50m) range.
• Best for PS5 and PC gaming → SUNITEC Auracast Transmitter USB-C. Direct USB-C connection to PS5, PC, MacBook, laptop and tablet, with aptX Adaptive for in-sync audio.
• Best for hearing-aid broadcasting → SUNITEC Auracast Transmitter USB-C. Its 24kHz mode is tuned for compatible Auracast hearing aids.
• Best for travel simplicity with no setup → Avantree Relay & SoundJet. Plug into AUX, pair your headphones, done — no host device or app needed.
• Best value depends on your use case → if you fly and share a screen, the Avantree earns its keep; if you game or broadcast, the SUNITEC does far more. Check the current price on Amazon for each before deciding.
My Verdict
which earbuds support aptx hd
That depends on the earbuds, not the transmitter. The transmitter side here is the SUNITEC Auracast Transmitter USB-C, which supports aptX HD and aptX Adaptive in Classic Bluetooth. Your earbuds must also support aptX HD to actually use it — check your model's spec sheet before buying.
Yes, for the broadcast side. Auracast Broadcast Mode requires compatible Auracast or LE Audio receiving devices like headphones, speakers or hearing aids. Classic Bluetooth mode works with standard Bluetooth headsets, but Auracast sharing needs compatible receivers.
No. The Avantree bundle is a Bluetooth transmitter for 3.5mm AUX sources only, and it is explicitly not compatible with TVs, hearing aids or musical instruments, and it does not pair with phones or tablets. It is aimed at airplane audio and similar AUX output jacks.
No. The BT400T supports audio playback only and does not support microphone input or voice chat. On PS5, for example, you would set the controller's microphone as the input device under Settings > Sound > Microphone instead.
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