We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-10-01 · 7 min read · Independent comparison
If you want a compact two-pack adapter that turns a USB-C port into a standard 3.5mm headphone jack for earbuds, wired headphones and MacBooks, choose Untvie USB-C; if you need a long 10ft cable to run audio from your phone into a car stereo's aux jack, choose MORELECS Aux.
• Untvie USB-C — biggest strength: A short USB-C-to-3.5mm adapter with a built-in DAC running at 48,000 samples per second, sold as a 2-pack. It's built to plug headphones into a phone or laptop that no longer has a headphone jack.
• Untvie USB-C — biggest trade-off: It's an adapter, not a long cable. "Compact shape" and pocket storage are the whole point, so it won't reach across a car cabin.
• MORELECS Aux — biggest strength: A 10ft braided USB-C-to-3.5mm cable with dual shielding (aluminum foil + OFC spiral) designed to kill engine hum and alternator whine in a car.
• MORELECS Aux — biggest trade-off: Audio output only, one direction, and it does not charge. Your voice on calls comes through the phone's mic, not the cable.
• Who each is for: Untvie USB-C is for headphone listeners on USB-C phones, tablets and laptops. MORELECS Aux is for drivers whose dash has a real round 3.5mm aux jack and who want the cable to reach the back seat.
The Untvie USB-C adapter is a tiny dongle that gives a jackless device a headphone port again. The pitch here is audio quality: a DAC converting at 48,000 samples per second, which the brand describes as lossless, with rich bass, clear highs and balanced mids. Whether or not you buy the marketing language, the spec tells you this is aimed at people who care about how their wired headphones sound rather than just getting any signal through.
The second thing that matters is compatibility, and the list is genuinely broad. It covers iPhone 17/16/15 series, Google Pixel 7/7 Pro/6/6 Pro/6a, the Galaxy S23/S22/S21/S20 families plus A53/A54 and the Z Flip and Z Fold lines, MacBook Pro and MacBook Air (2020/M1/M2), iPad Pro 2018–2022, iPad Air 2020/2022 and iPad mini 2021. If your phone or tablet dropped the headphone jack in the last several years, there's a good chance it's on that list.
Build-wise, it's a TPE cable with an aluminum alloy shell, anti-tangle and anti-bend, and the brand says it's certified to pass 25,000+ bending tests. That's a durability claim from the manufacturer, not an independent lab result, but it does tell you the design intent: survive being shoved in a bag. It ships as a 2-pack, which is the practical detail I like most — one stays in the laptop bag, one lives in your pocket, and you're not stuck when one goes missing.
Buy it if you want to keep using wired headphones or earbuds on a USB-C phone, iPad or MacBook and you'd rather not carry a long cable. Skip it if your goal is car audio from a dash aux jack, or if you need a cable long enough to reach a rear seat — this is the wrong shape for that job.
MORELECS Aux is a different animal entirely: a 10ft USB-C-to-3.5mm cable built for a car. The critical requirement is stated plainly — your vehicle needs a real 3.5mm aux jack, the small round pencil-eraser-sized hole usually labeled "AUX" or "Line In." It will not work through a car's USB port (those are charging-only), through a Bluetooth-only head unit, or in a car with no auxiliary input at all. Check your dash before you buy; this is the single most common way people end up disappointed with any cable like this.
What the design actually solves is noise. Most cheap aux cables pick up engine hum, alternator whine and charger interference. This one uses two shielding layers — 360-degree aluminum foil for high-frequency EMI/RFI, and an Oxygen-Free Copper spiral braid for low-frequency noise from the engine and alternator. That's a real, spec-level answer to a real problem, and it's the strongest argument for this cable over a generic one.
The 10ft length is the other headline. That reaches from a dashboard jack to rear passengers, truck bench seats or a center-console phone mount without stretching. It's nylon braided and tangle-free, with aluminum alloy connectors, gold-plated contacts and an elongated SR transition zone at the plug — a detail aimed at the spot where cables usually fail first. A slim step-down design means it fits most phone cases without removal.
Two limitations to be clear about. It's audio output only and one-directional: your phone sends audio out to the car, headphones or speaker, and you can't reverse that. On calls, the other person's voice plays through the car speakers, but your voice is picked up by your phone's mic, not the cable — so no external mic, no voice-chat input, no instrument recording. And it doesn't charge. It's a DAC cable, not a power cable. Volume is also just phone output times stereo output; the DAC chip converts cleanly but doesn't amplify, and Samsung phones typically output louder than iPhones over aux. Turn both to max and disable any media volume limiter.
Side-by-Side: Which Should You Choose?
• Best for wired headphone listening on a USB-C phone or laptop → Untvie USB-C. That's its entire purpose, and the 48,000 samples/second DAC spec is the headline feature.
• Best for car stereo audio → MORELECS Aux. The 10ft reach and dual shielding are designed specifically for dashboard-to-rear-seat runs in a noisy vehicle.
• Best for travel and pocket carry → Untvie USB-C. Compact, lightweight, and you get two of them.
• Best for noisy environments → MORELECS Aux. The aluminum foil plus OFC spiral shielding is aimed squarely at engine and alternator interference.
• Best for long-term durability at the plug → MORELECS Aux. Reinforced SR tapered joint, gold-plated contacts and double-braided nylon.
• Best for surviving everyday abuse → Untvie USB-C. The 25,000+ bending-test claim and TPE-and-aluminum build are about flexing and stuffing into bags.
• Best if you need mic input or charging → neither. MORELECS Aux is output-only and doesn't charge; Untvie USB-C is a headphone adapter, not a power or mic solution.
• Best for households with multiple devices → Untvie USB-C. The 2-pack spreads across a phone, an iPad and a laptop.
In my opinion, these two aren't really competitors — they solve different problems, and the "better" one depends entirely on your setup. If I had to pick one for the most people, I'd take the MORELECS Aux, because car audio is where a cheap cable fails most audibly (hum, whine, dropouts) and where the 10ft reach genuinely changes daily use. But if you're a headphone person on a modern USB-C phone or a MacBook, the Untvie USB-C is the smarter buy — compact, compatible with a huge device list, and you get two. Buy for your actual port and your actual distance, not for the category.
No. It needs a real 3.5mm aux jack on your dash or console. Car USB ports are charging-only and won't play audio, and Bluetooth-only head units won't work either. If you can see a small round aux hole, you're fine.
You can plug it into a car aux jack if you also have a separate 3.5mm cable, but that's not what it's built for. It's a short adapter meant to give headphones a jack on a USB-C phone, tablet or laptop — not a long car run.
Partly. The other person's voice plays through your car speakers, but your voice is captured by your phone's microphone, not the cable. It doesn't support external mic input, voice chat apps or instrument recording.
No. Neither product is a charging cable. The MORELECS Aux is audio-output only and one-directional, and the Untvie USB-C adapter simply converts USB-C to a 3.5mm headphone jack. Keep your regular charging cable for power.
Both are budget accessories, but I won't quote numbers here. Check the current price on Amazon using the button on this page before you decide.
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