Modular IEM Cable Guide: One Cable for Phone, Dongle and DAP

A modular IEM cable is an earphone cable with a detachable player plug, so one cable can switch between a 3.5 mm, a 4.4 mm balanced and a USB-C DAC plug. You change the plug, not the cable. Our Ethos Ultra works this way: it costs from USD 89, and all three plugs come in the box.

This guide is for anyone who listens on a phone on the move, a dongle at work and a digital audio player (DAP) at home, and wants one modular IEM cable instead of three. You'll learn how the swappable plug works, which plug suits which source, where the limits are and what to check before you order.

What is a modular IEM cable?

A modular IEM cable is a cable built in parts that you can separate and recombine. Most often the modular part is the player end: the plug that goes into your phone, dongle or DAP. A fixed-plug cable, by contrast, has one plug soldered on for its whole life.

Modularity can sit at either end. At the player end, it lets one cable feed different sources. At the earphone end, it lets one cable fit IEMs with different connectors. Ethos Ultra is modular at the player end as standard, and can be modular at the earphone end as well with FlexiPlug.

The idea is practical. The conductors, which are the costly part of a cable, stay the same. Only the plug changes.

Why swap the plug instead of carrying adapters?

If you own more than one source, each may want a different plug. Phones use USB-C or, on older iPhones, Lightning. Most current players and USB DACs have a 4.4 mm balanced output. Older players, amps and computers often have 3.5 mm.

The plugs are not interchangeable electrically. A 3.5 mm single-ended plug has 3 contacts: left, right and a shared ground. A 4.4 mm balanced plug has 5 contacts, four for signal and one for ground, so each channel has its own return wire. JEITA added the 4.4 mm 5-pole plug to its standard RC-8141C in 2016 (Phile-web). Our guide to 3.5 mm, 2.5 mm or 4.4 mm balanced explains the difference in full.

Adapters work, but each one adds a joint and some bulk. A balanced cable should only go into a 3.5 mm socket through an adapter made for it. Buying a second or third cable costs more and gives you more to carry. A modular IEM cable solves the same problem with one cable and a set of plugs.

How does Ethos Ultra work as a modular IEM cable?

Ethos Ultra is the coaxial evolution of our Ethos line. It has three parts that matter here: the swappable player end, the coaxial cable and the USB-C DAC plug.

The screw-locking player end

The player end is detachable. A threaded collar locks each plug onto a 4-pin connector at the end of the cable. To swap plugs, you unscrew the collar fully, then pull the plug straight out. The 3.5 mm single-ended, 4.4 mm balanced and USB-C DAC plugs are all included.

The coaxial cable

A coaxial cable is a cable in which one conductor runs down the centre and a second conductor is wound around it. In Ethos Ultra, each channel is its own coaxial line. The signal conductor is 5N single-crystal copper, 7 × 7 × 0.08 mm, about 23 AWG. A silver-plated copper spiral shield around it carries the return and shields the signal at the same time.

Because each channel keeps its own return all the way to the 4-pin connector, the 4.4 mm balanced plug is native. A Kevlar fibre core takes the pulling strain, so the copper isn't stretched when the cable is tugged or coiled. Each lead is 2.5 mm across, under a clear, yellowing-resistant jacket. The cable is 1.2 m long and weighs about 35 g.

Sound descriptions are our own: we describe the single-crystal copper as adding weight to the mids and bass, with the silver-plated shield keeping the treble open.

The USB-C DAC plug

A DAC (digital-to-analogue converter) is the circuit that turns digital audio into the analogue signal your IEMs play. Ethos Ultra's USB-C plug is a complete 32-bit / 384 kHz DAC with a built-in Class G amplifier. It is made for IEMs and drives earphones from 16 Ω directly.

The plug also stores a 5-band parametric EQ, adjustable from 20 Hz to 20 kHz by up to ±12 dB per band. You set it in the Null Audio PEQ app on Android, or at peq.null-audio.com in Chrome or Edge on a computer, then write it to the DAC. After that, the same tuning plays on iPhone and Android with no app.

Which plug for your phone, dongle or DAP?

Match the plug to the socket you are using today. With Ethos Ultra, you can change your mind tomorrow.

• Phone or tablet: use the USB-C DAC plug. iPhone 15 and later have USB-C; iPhone 5 to iPhone 14 used Lightning (Apple). Ethos Ultra has no Lightning plug, but our other cables can be built with one; see USB-C IEM cables.
• Laptop: the USB-C DAC works with Windows, macOS and Linux as a standard USB audio device, with no driver needed.
• Dongle or DAP with a 4.4 mm output: use the 4.4 mm balanced plug. Our 4.4 mm balanced IEM cable page lists which players have one.
• 3.5 mm output: use the 3.5 mm single-ended plug, for older players, amps and computers.
• Full-size or hard-to-drive headphones: use the 3.5 mm or 4.4 mm plug with a dedicated amplifier rather than the USB-C DAC.

For the wider choice between a DAC cable, a dongle and Bluetooth, read IEMs with your phone. If you also take calls, our guide to the IEM cable with mic covers microphone options.

Can the earphone end be modular too?

Yes. FlexiPlug is our interchangeable earphone-side system: one cable with swappable tips for 0.78 mm 2-pin, IE 300/600/900 MMCX, IPX, A2DC, qdc 2-pin and Pentaconn Ear. Choose FlexiPlug as the earphone connector on Ethos Ultra, and both ends of the cable become swappable.

FlexiPlug suits you if you own IEMs with different connectors. If you own one pair, choose its own connector instead. Our standard 2PIN (0.78) plug fits both flat and recessed 2-pin sockets. Ear guides of about 10 cm come fitted by default on common connectors such as 2-pin, MMCX and IPX.

Earphone connectors also differ in how well they take repeated swapping. Audio-Technica lists loose fit, overly tight fit and dropouts on rotation among MMCX problems (Audio-Technica). Pentaconn Ear was designed for durability over many insertions (Porta-fi). For each type, see 2-pin, MMCX, IPX or Pentaconn Ear and our IEM connector guide. Owners of recessed-MMCX Sennheiser models can start with the Sennheiser IE series guide.

Modular IEM cable or fixed plug: which suits you?

A modular cable is not the right answer for everyone. If you only ever use one source, a fixed plug is simpler and lighter.

Both Ethos models start from USD 89 and are 1.2 m long. The difference is in construction: Ethos MKVII is a braided silver-plated copper cable with one plug, while Ethos Ultra is coaxial with three. For conductors and budgets across the range, see How to choose an earphone cable.

How to order Ethos Ultra

1. Find your IEM's connector in Find My Cable, which covers 400+ models.
2. Choose that connector, or FlexiPlug, in the configurator on the Ethos Ultra page.
3. You don't need to choose a player plug: 3.5 mm, 4.4 mm and USB-C DAC all come in the box, with a leather pouch.

The 0.78 mm 2-pin version is in stock and ships in 1–2 working days. Other connectors are built to order by hand in Singapore, with a lead time of around 1 week. We ship worldwide with FedEx, free from USD 250.

Every cable carries a 1-year warranty, and Ethos Ultra can be repaired at a flat rate of USD 30 within 3 years of purchase; see our warranty page. To keep the screw lock and plugs in good order, read How to make your IEM cable last. For a custom length or a question about your setup, contact us.

Frequently asked questions