We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-09-29 · 7 min read · Independent comparison
If you want a long, no-fuss analog audio extension that just works with anything that has a round headphone jack, choose FONVOi 20FT; if you need to listen on a modern USB-C phone while charging it at the same time, choose Marsno USB C. These two cables solve completely different problems, and that is the whole story here.
• FONVOi 20FT biggest strength: a 20-foot male-to-female 3.5mm TRS extension with a nylon braid rated for 10,000+ bends and gold-plated connectors — pure reach and durability, no electronics inside.
• FONVOi 20FT biggest trade-off: it is TRS only. No microphone, no inline call button, and it only passes audio in one direction.
• Marsno USB C biggest strength: a 2-in-1 USB-C adapter that gives you a 3.5mm headphone jack and up to 60W PD charging through the same dongle, with a built-in DAC for clean decoding.
• Marsno USB C biggest trade-off: it is an active adapter, so it has real compatibility asterisks — no data transfer, no OMTP support, no QC 3.0, and Apple EarPods' mic won't work.
• Who FONVOi 20FT is for: anyone extending a headphone, speaker or car AUX connection across a room, a studio or a vehicle.
• Who Marsno USB C is for: anyone whose phone or tablet dropped the headphone jack and who wants to charge and listen at the same time.
The FONVOi 20FT is a straightforward analog cable, and I mean that as a compliment. It is a 20-foot male-to-female 3.5mm TRS extension: a gold-plated male plug on one end, a female jack on the other, and twenty feet of braided nylon-sheathed cable in between. Inside, FONVOi uses a pure copper core with shielding designed to push back interference, wrapped in a TPE jacket and then finished with that nylon braid — the spec sheet calls out a 10,000+ bend rating, which tells you the target here is a cable that survives being coiled, yanked and stuffed in a bag for years.
What it does best is distance. Twenty feet is genuinely long — enough to run from a TV or receiver to a couch, from a desk interface to a chair across the room, or from a phone in the console to a passenger in the back seat. Because there is no chip inside, there is nothing to handshake, nothing to heat up, and nothing to fail. You plug it in and audio comes out the other end. The female end also protects the jack on your expensive device: instead of unplugging your headphones from your laptop or tablet over and over, you wear out the cheap extension instead.
Who should buy it: anyone with devices that still have a standard 3.5mm jack — portable speakers, headphones, MP3 players, receivers, car stereos, older iPhones and iPads, Android phones and tablets, Surface devices and the like. If your problem is "the cable is too short," this is the fix.
Who should skip it: anyone who needs a microphone line. FONVOi is explicit that this is a TRS link — three pins, audio in one direction only — and it does not support mic function. If you need to make calls or use a headset mic, you want a TRRS cable instead. Also skip it if your phone has no headphone jack at all; a plain extension can't create a port that isn't there.
The Marsno USB C is a different animal entirely. It is a 2-in-1 USB-C to 3.5mm adapter that splits one USB-C port into two jobs: a headphone jack and a charging passthrough rated up to 60W Power Delivery. That combination is the entire point. On a phone with no headphone jack, the usual dongle forces a choice — charge, or listen. Marsno's answer is both at once, which matters on long flights, overnight gaming sessions, or any day where you're streaming and your battery is already low.
It's not a dumb passthrough, either. There's a smart DAC decoding chip inside for stable audio conversion, and Marsno claims clean, low-noise output without the current hiss you sometimes get from cheap adapters. Charging is managed by an EJ899M chip to keep voltage and current steady, and the whole thing is plug-and-play with no driver needed. It also supports in-line remote control, so volume and track buttons on a wired headset generally keep working. Marsno backs it with a 24-month warranty and 24/7 support — a longer coverage window than most dongles bother with.
The trade-offs are real and you should read them before buying. No data transfer — this is audio and power only. No OMTP support, and it follows the CTIA standard, so older OMTP-style headsets are out. Apple EarPods with a 3.5mm plug won't pass their microphone through it. QC 3.0 charging isn't supported, and Marsno recommends a PD wall charger; Samsung Super Fast Charging isn't supported either. The calling function won't work on a phone that already has its own 3.5mm jack, and on iPad Pro 2018 the wire control and calling functions don't work. OnePlus, Amazon Fire Max, GoPro, Switch and Moto aren't covered across all models, and separate microphone accessories aren't supported. If you hear echo on a call, Marsno's guidance is to try a better wired headset; if you hear noise while charging, swap in the original charger.
Who should buy it: owners of modern USB-C phones and tablets — iPhone 15 through 17 series, Galaxy S25/S24/S23 and older S-series, Pixel, iPad Pro, Huawei and Xiaomi models — who want wired audio and charging simultaneously.
Who should skip it: anyone who needs data sync through that port, anyone with an OMTP headset, and anyone expecting it to behave identically across every Android brand.
• Best for reach and cable length → FONVOi 20FT. Twenty feet of extension versus a short dongle; nothing on the Marsno side competes on distance.
• Best for listening while charging → Marsno USB C. Up to 60W PD passthrough is the feature FONVOi simply doesn't have.
• Best for microphone and calls → neither, strictly speaking. FONVOi is TRS with no mic support, and Marsno won't pass Apple EarPods' mic. If calls are the priority, check your headset standard carefully.
• Best for devices that still have a headphone jack → FONVOi 20FT. It's built for exactly those ports, and it protects them from repeated plugging.
• Best for USB-C phones with no headphone jack → Marsno USB C. It's the only one of the two that can give a jackless phone a wired audio path at all.
• Best for durability with zero electronics to fail → FONVOi 20FT. Braided nylon, 10,000+ bend rating, no chips, no firmware, no charging logic.
• Best for travel with one port → Marsno USB C. One dongle replaces the "charge or listen" dilemma, though you'll want a PD charger on hand.
• Best for maximum compatibility across old gear → FONVOi 20FT. Its only hard requirement is a 3.5mm jack and no mic need.
In my opinion, the right pick comes down to one question: does your device still have a headphone jack? If yes, I would buy the FONVOi 20FT. It's a passive, overbuilt extension with nothing to go wrong, and twenty feet of reach solves a problem no dongle can. If your phone or tablet is USB-C-only and you hate choosing between music and a charge, I would buy the Marsno USB C — it's the more capable product, as long as you accept its compatibility caveats. If you're on the fence, buy for the port you actually own today, not the one you might own later.
FAQ
Yes, for audio. FONVOi lists iPhone, iPad, iPod, Android phones and tablets, Surface, MP3 players, receivers and car stereos — anything with a standard 3.5mm jack. Just remember it's TRS, so no microphone and no inline call button.
Yes — that's its main feature. It supports up to 60W PD charging while passing audio through the 3.5mm jack. Marsno notes QC 3.0 and Samsung Super Fast Charging aren't supported, and recommends a PD wall charger.
No. Marsno states clearly that data transfer is not supported. It handles audio output and power delivery only, so keep a separate cable for syncing.
That depends on what you need, not on the number. If you need a long extension, the FONVOi 20FT does one thing well with no electronics to fail. If you need simultaneous audio and charging on a USB-C phone, the Marsno USB C is doing far more work and carries a 24-month warranty. Check the current price on Amazon for each before deciding, since the page's button will show you today's figures.
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