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If you want the most versatile, audiophile-grade Bluetooth adapter for a TV, home stereo or soundbar, choose 1Mii B03S; if you need a pocket travel adapter that keeps two people watching the same in-flight movie on their own headphones, choose Avantree Relay & SoundJet. These two products barely compete for the same job — and that's the most useful thing I can tell you up front.
• 1Mii B03S — biggest strength: A true 2-in-1 transmitter and receiver with optical, RCA and 3.5mm connections, a SABRE DAC, aptX Adaptive/LL/HD and dual-antenna Class 1 range up to 265ft in open space. It's a home-audio hub.
• 1Mii B03S — biggest trade-off: It's corded (no battery), it's a tabletop box rather than a pocket device, and it can't run transmit and receive modes at the same time.
• Avantree Relay & SoundJet — biggest strength: Purpose-built for flights. It pairs two Bluetooth headphones at once, runs up to 25 hours per charge, and its 3.5mm AUX input plugs straight into an airplane seat's headphone jack.
• Avantree Relay & SoundJet — biggest trade-off: It's a transmitter only, and Avantree explicitly states it is not for TVs, phones or hearing aids — so it solves exactly one problem very well.
• Who each is for: 1Mii B03S is for the living room — TVs, receivers, soundbars, old stereos and wired speakers. Avantree Relay & SoundJet is for the seat-back tray table.
The B03S is the one I'd call the "everything box." It works in two directions: transmit mode takes audio from your TV, AV receiver or radio and sends it wirelessly to Bluetooth headphones or a speaker, while receiver mode takes music from your phone or tablet and pushes it into an older wired stereo. There's also a bypass mode so a soundbar or wired setup can keep working without you unplugging anything. That flexibility is the whole point of buying it.
On the audio side, 1Mii pairs a SABRE DAC with Qualcomm chipsets and supports aptX Adaptive, aptX Low Latency and aptX HD. In plain terms: aptX LL keeps lip-sync tight for movies, aptX HD aims at higher-resolution music, and aptX Adaptive tries to balance the two. It also supports dual connections, so two sets of headphones can be paired at once. One caveat straight from 1Mii's own notes — if you pair two aptX Low Latency headphones at the same time, the codec drops to standard aptX for stability. And to actually get aptX LL/HD/Adaptive, your headphones have to support the same codec.
Buy it if you want one adapter that can feed wireless headphones from your TV and breathe Bluetooth into an old hi-fi. Skip it if you mainly need something for flights, or if you want a battery-powered device you can carry in a bag — the B03S is a stay-at-home box.
Avantree Relay & SoundJet: Who It's For
The Relay & SoundJet R1 does one thing, and it does it with clear intent: it turns an airplane seat's wired 3.5mm jack into a Bluetooth signal, so you can use your own AirPods, Bose or other wireless headphones instead of the airline's. You plug the adapter into the seat-back port; it transmits to your headphones. That's the entire workflow, and for frequent flyers it's a genuinely nice quality-of-life upgrade.
The headline feature is dual pairing. Two Bluetooth headphones can connect at the same time, which means you and a travel partner can watch the same movie side by side, each at your own volume. Anyone who has shared a single pair of earbuds on a long flight knows why that matters.
Audio runs on Qualcomm aptX Adaptive, which Avantree describes as delivering balanced sound and dependable wireless performance. The 3.5mm AUX input is the only input, and it's battery powered — rated at up to 25 hours of playtime per charge, which comfortably covers long international flights and even multi-leg travel days.
The flip side is the compatibility list, and Avantree is refreshingly blunt about it: the Relay & SoundJet is not for TVs, phones, hearing aids or musical instruments, and it won't pair with phones or tablets. It's a transmitter only. If you were hoping to also use it at home with your TV, that's a hard no — that's the B03S's job. Buy it if you fly often and want to use your own headphones, especially as a couple. Skip it if your problem is home audio rather than in-flight audio.
Side-by-Side: Which Should You Choose?
• Best for TV and home stereo → 1Mii B03S. Optical, RCA and 3.5mm in/out, plus transmit, receive and bypass modes.
• Best for flights and travel → Avantree Relay & SoundJet. 3.5mm AUX into the seat jack, battery powered, built for the tray table.
• Best for two listeners on a plane → Avantree Relay & SoundJet. Two headphones paired simultaneously — its single clearest advantage.
• Best for battery freedom → Avantree Relay & SoundJet. Up to 25 hours per charge, no cable needed. The B03S is corded electric, so it never needs charging but never travels light.
• Best for range → 1Mii B03S. Class 1 Bluetooth with dual antennas, rated to 265ft open space and 80–110ft indoors.
• Best for codec flexibility → 1Mii B03S. aptX Adaptive, aptX LL and aptX HD, with a SABRE DAC. The Relay & SoundJet centers on aptX Adaptive alone.
• Best for old wired speakers → 1Mii B03S. Receiver mode turns a phone or tablet into the source for a legacy stereo. The Avantree can't do this at all.
In my opinion, the 1Mii B03S is the better buy for most people, simply because it does more: two-way operation, optical and analog connections, aptX LL/HD/Adaptive, a SABRE DAC and long-range dual antennas. It's the adapter you buy once for the living room. I'd only steer you to the Avantree Relay & SoundJet if flying is your actual pain point — it's superb at that one job, with dual-headphone pairing and 25 hours of battery, but it's deliberately walled off from TVs, phones and hearing aids. If you're a frequent flyer, buy the Avantree; otherwise, the 1Mii B03S is the one I'd put in my cart.
They solve different problems. The B03S is a home-audio transmitter and receiver with optical/RCA/3.5mm and long range; the Avantree is a battery-powered airplane transmitter for two headphones. Neither replaces the other.
Can I use the Avantree Relay & SoundJet with my TV?
No. Avantree states it is not compatible with TVs, phones or hearing aids, and it won't pair with phones or tablets. For TV use, the 1Mii B03S is the appropriate pick.
Only the Avantree has a battery — up to 25 hours of playtime per charge. The 1Mii B03S is corded electric, so it runs continuously from power with no charging at all.
For the 1Mii B03S, yes — aptX Low Latency, HD or Adaptive only work if your headphones support the matching codec. The Avantree relies on aptX Adaptive, so your headphones need that support to benefit.
That depends on your use case rather than the spec sheet, so check the current price on Amazon for both and weigh it against how often you'd actually use each one. If you need home-audio flexibility, the B03S covers more ground; if you fly often, the Avantree earns its place in your bag.
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