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We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-10-01 · 6 min read · Independent comparison
• Avantree Relay & SoundJet — biggest strength: a Qualcomm chipset with aptX Adaptive and aptX HD over Bluetooth 5.3, plus dual-headphone support so two people can watch the same movie in sync.
• Avantree Relay & SoundJet — biggest trade-off: it is a 3.5mm AUX transmitter only. Avantree states it is not compatible with phones, car stereos or hearing aids, so it is a travel and gym tool rather than a do-everything adapter.
• SUNITEC Auracast Transmitter USB-C — biggest strength: one-to-many broadcast. It can send audio to virtually unlimited Auracast-compatible headphones, speakers and hearing aids, with up to 164ft (50m) of broadcast range in Auracast mode.
• SUNITEC Auracast Transmitter USB-C — biggest trade-off: it is audio playback only. There is no microphone input or voice chat, and Auracast mode only works with Auracast or LE Audio receiving devices.
• Who each pick is for: Avantree suits flyers and gym users with aptX HD earbuds or headphones who want to share audio with a partner; SUNITEC suits gamers, presenters and assistive-listening users who need to beam one source to many devices.
The Avantree Relay & SoundJet is a compact 3.5mm AUX Bluetooth transmitter. Its pitch is quality and simplicity: a premium Qualcomm chipset driving aptX Adaptive and aptX HD, with Bluetooth 5.3 for stability. If you own aptX HD earbuds, this is the interesting part — the adapter is built to feed that codec rather than fall back to a basic stream. Plug it into an airplane seat's headphone jack and your own headphones receive the audio wirelessly.
The second thing it does well is sharing. Avantree says it can connect two Bluetooth headphones at once with the audio staying in sync, which is genuinely useful when you and a travel companion want to watch the same in-flight movie without splitting a single headset. It also lists up to 25 hours of continuous playback — enough for long-haul flights — with LED connection indicators and onboard buttons for pairing and volume. The whole thing is lightweight and pocket-sized.
Who should skip it? Anyone expecting a universal adapter. Avantree is explicit that this is not for phones, car stereos or hearing aids, and its job is streaming from a 3.5mm AUX source such as airplane entertainment. It is also not the tool for broadcasting to a room of listeners; its ceiling is two headphones. If your priority is aptX HD audio from a wired source with a friend beside you, it fits neatly. If you need to send audio to a crowd, it does not.
The SUNITEC Auracast Transmitter USB-C (model BT400T) is a different animal: a tiny USB-C dongle, roughly 32 x 21.8 x 7.8mm and about 2.8g, that plugs into a PS5, PC, MacBook, laptop, tablet, iPhone 15/16/17, Android phone or other USB-C device. No drivers, no apps. One button flips it between Classic Bluetooth for a single headset and Auracast Broadcast Mode for many listeners at once.
That broadcast mode is the headline. SUNITEC quotes up to 33ft (10m) in Bluetooth mode and up to 164ft (50m) in Auracast mode, and compatible devices can discover and join the broadcast without pairing. Codec support is broad: AAC, SBC, aptX, aptX Adaptive and aptX HD over Classic Bluetooth, and LC3 for Auracast. There is also a thoughtful two-mode switch — 24kHz for compatible Auracast hearing aids, 48kHz for Auracast headphones and speakers.
The trade-offs are worth stating plainly. It is playback only: no microphone input, no voice chat, so on PS5 you would route chat through the controller mic. Auracast mode is useless unless your receiving gear supports Auracast or LE Audio. And the iPhone quirk is real — if the headset does not connect within 15 seconds, SUNITEC says to start music first to trigger transmission. Buy it if you game, present, teach or use assistive listening and want one source feeding many devices.
• Best for in-flight movies → Avantree Relay & SoundJet. It plugs into a 3.5mm AUX jack, which is exactly what airplane seats provide.
• Best for aptX HD earbuds from a wired source → Avantree Relay & SoundJet. aptX Adaptive and aptX HD over Bluetooth 5.3 is its core design goal.
• Best for sharing with one companion → Avantree Relay & SoundJet. Two headphones, synced, from a single source.
• Best for long sessions away from power → Avantree Relay & SoundJet. Up to 25 hours of continuous playback.
• Best for gaming on PS5 or PC → SUNITEC Auracast Transmitter USB-C. USB-C plug-and-play with aptX Adaptive and aptX HD to keep audio responsive.
• Best for one-to-many broadcasting → SUNITEC Auracast Transmitter USB-C. Virtually unlimited Auracast receivers, up to 164ft (50m).
• Best for hearing aids and assistive listening → SUNITEC Auracast Transmitter USB-C. The 24kHz mode is aimed at compatible Auracast hearing aids.
• Best for the widest range of sources → SUNITEC Auracast Transmitter USB-C. Phone, tablet, laptop, desktop, PS5 — anything with USB-C.
• Skip Avantree if you need phone, car or hearing-aid support, or voice chat. Skip SUNITEC if you need a 3.5mm AUX input or microphone passthrough.
In my opinion, the choice comes down to your source and your audience. If you fly, use aptX HD earbuds and want to share a movie with the person next to you, I would buy the Avantree Relay & SoundJet — the 3.5mm AUX design, dual-headphone sync and up to 25 hours of playback fit that job precisely. If you game on PS5 or PC, or you need to broadcast one audio stream to many headsets, speakers or hearing aids, I would buy the SUNITEC Auracast Transmitter USB-C instead. They overlap on aptX HD support, but they solve different problems. Check the current price on Amazon before deciding, since both are inexpensive-looking gadgets with very different capabilities.
FAQ
which earbuds support aptx hd
For Auracast Broadcast Mode, yes. SUNITEC states Auracast mode requires compatible Auracast or LE Audio receiving devices, and those devices can join the broadcast without pairing. In standard Classic Bluetooth mode, it works with ordinary Bluetooth headsets instead.
No. Avantree explicitly lists phones, car stereos and hearing aids as incompatible with the Relay & SoundJet. It is designed to take audio from a 3.5mm AUX source such as an airplane seat and transmit it to Bluetooth headphones.
No. SUNITEC notes the BT400T is audio playback only and does not support microphone input or voice chat. For PS5 voice chat you would use the controller's microphone under Settings > Sound > Microphone > Input Device > Controller Microphone.
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