We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-09-25 · 7 min read · Independent comparison
If you want to turn an older TV, home stereo or PC into a two-headphone wireless setup with a real screen and physical controls, choose Ainostone Transmitter Receiver 3-in-1; if you need headphones you can actually wear in the pool, choose Feiltik Swimming Headphones Underwater. These two products barely overlap. One is a desktop audio adapter. The other is a wearable MP3 player built for water. The only real reason they end up in the same shopping cart is the word "Bluetooth" — and that word means something very different in each box.
• Ainostone's biggest strength: a 3-in-1 Bluetooth 5.3 adapter with TX, RX and Bypass modes, an external antenna, a 1.8-inch LCD, and wired inputs across Optical, 3.5mm Aux and RCA — it connects to almost any legacy audio gear you own.
• Ainostone's biggest trade-off: it has no battery at all. It must stay plugged into USB power, and it will not work with amplifiers such as Yamaha amps or audio converters.
• Feiltik's biggest strength: true IPX8 waterproofing plus 32GB of built-in storage, so you can swim, dive or snorkel with music and never rely on a wireless signal.
• Feiltik's biggest trade-off: Bluetooth does not work underwater. You must switch to MP3 mode before you get in the water, and there is no noise control at all.
• Pick Ainostone if your problem is a TV, stereo or PC that needs a wireless audio bridge — especially if two people want to listen at once.
• Pick Feiltik if your problem is wanting music in the pool without your ears hurting.
This is a bridge device, not a listening device. It sits near your TV, receiver or computer, plugs into USB power, and converts audio in both directions. In TX mode it takes sound from a wired source and beams it to Bluetooth headphones or speakers. In RX mode it does the reverse, pulling a Bluetooth signal from your phone and pushing it into a wired stereo. There is also a Bypass mode, which matters more than people expect — it lets audio pass through untouched when you do not want the adapter in the chain at all.
The headline feature is two-device pairing in TX mode. You and a partner can each wear your own Bluetooth headphones and watch the same movie late at night without waking anyone else. Both volumes move together when you turn the knob, which is either convenient or annoying depending on how different your hearing is. Ainostone also calls out hearing-impaired users as a good fit, which makes sense: one source, two headsets, independent comfortable volume for each person.
Setup is deliberately unglamorous. You power it over Type-C, pick TX, RX or Bypass, then connect. The 1.8-inch LCD tells you what is connected instead of leaving you guessing with blinking lights, and the adapter re-pairs with the most recent device automatically. Cables for Optical, 3.5mm and RCA are included, so a TV, PC, laptop, CD player or home stereo are all fair game.
Skip it if you want something portable, if you game competitively, or if your audio chain runs through an amplifier the adapter does not support.
Feiltik Swimming Headphones Underwater: Who It's For
Feiltik solves a completely different problem. These are open-ear bone conduction headphones rated IPX8 — fully waterproof for swimming, diving, snorkeling and general water sports. Bone conduction drivers send sound through your cheekbones rather than into your ear canals, so your ears stay open and unblocked. No pressure, no soreness after long sessions. If in-ear buds have ever made your ears ache, that design difference is the whole point.
The critical detail is the 32GB of built-in memory. That is roughly 8,000 songs stored on the headset itself, played back in MP3 mode. Why does that matter? Because Bluetooth does not work underwater. Radio signals do not travel through water, so any wireless earbud dies the moment you submerge. Feiltik sidesteps that entirely: load your music, switch to MP3 mode, get in the pool. That is the honest, correct engineering answer to underwater listening.
On land, it flips back to wireless. Bluetooth 6.0 handles the connection, and dual device pairing means you can keep two sources linked at once — phone and laptop, for example. Charging is magnetic, which removes the usual weak point on waterproof gear: no rubber flap to lose, no exposed port to leak. A protective case, swimming earplugs and a magnetic charging cable come in the box. Feiltik backs it with a one-year warranty, and the beige colorway is the only finish listed.
What it is not: it has no active noise control, no headphone jack, and no transparency mode in the sense premium earbuds use that term. The open-ear design gives you natural awareness of your surroundings instead, which for swimming is arguably safer. The bone conduction driver also means less bass thump than a sealed in-ear — that is physics, not a defect.
Side-by-Side: Which Should You Choose?
• Best for late-night TV with a partner → Ainostone Transmitter Receiver 3-in-1. Two Bluetooth headsets, one source, one volume knob.
• Best for swimming, diving or snorkeling → Feiltik Swimming Headphones Underwater. IPX8 plus 32GB of onboard music is the only setup that actually works submerged.
• Best for connecting old gear → Ainostone. Optical, 3.5mm Aux and RCA inputs cover TVs, stereos, PCs and CD players.
• Best for portability → Feiltik. It is a wearable with its own storage; Ainostone is a stationary box that needs constant USB power.
• Best for hearing-impaired listeners → Ainostone. The dual-headphone TX mode lets two people set their own comfortable volume.
• Best for low-latency gaming → neither, honestly. Ainostone states 200–300ms of inherent Bluetooth delay, and Feiltik's wireless mode is for land use, not competitive timing.
• Best for ear comfort during long sessions → Feiltik. Open-ear bone conduction avoids ear-canal soreness by design.
• Best for a single-purpose, no-surprises purchase → Feiltik, if water is your use case. Fewer moving parts, fewer setup steps.
In my opinion, these are not competitors and you should not agonize over the choice. If you have a TV, stereo or PC that needs a wireless audio bridge — especially a two-headphone one — I recommend the Ainostone Transmitter Receiver 3-in-1. The LCD, the external antenna and the three modes make it genuinely usable rather than a guessing game, as long as you accept the USB tether and the latency caveat. If you want music while you swim, I recommend the Feiltik Swimming Headphones Underwater without hesitation, because 32GB of onboard MP3 storage is the only approach that survives being underwater. Buy the one that matches your actual problem. Check the current price on Amazon for whichever fits, and confirm your specific gear compatibility first.
FAQ
how to turn airpods to transparency mode
which airpods have transparency mode
Transparency mode arrived with AirPods Pro and has carried through later generations, including AirPods Pro 2 and AirPods 4 with active noise cancellation. Standard earlier AirPods do not have it. This is worth knowing because neither product in this comparison has noise cancellation or transparency at all — Feiltik explicitly lists noise control as none.
do all airpods have transparency mode
No. It depends on the model and whether the hardware includes active noise cancellation, which transparency mode relies on. Base-model AirPods from earlier generations do not offer it. If that feature is your priority, you are shopping in a different category than either the Ainostone adapter or the Feiltik swimming headset.
what headphones have transparency mode
Transparency mode shows up mainly on over-ear and in-ear headphones that also offer active noise cancellation — typically flagship wireless models from the major audio brands. Neither product here qualifies: Ainostone is a transmitter/receiver adapter, not a headphone, and Feiltik is an open-ear bone conduction headset with no noise control listed.
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See also: Ainostone Transmitter Receiver 3-in-1 vs myFirst CareBuds Kids Earbuds, TREBLAB XR500 vs GREYOLK Swimming Headphones, Sony MDR-XB300 vs Jrumz Clarity CL01: Deep Bass Headphones