Our take

 

A tiny wireless amp with a screen — clip it on, stream to it over Bluetooth, and give any earphone real power without a cable to your pocket.

 

What it'll drive :

Every earphone VividSound sells runs easily from the W4 — IEMs don't need much power, and the balanced output has plenty in reserve. It stays quiet enough for sensitive sets like the Mystic 8, and has enough headroom that even full-size headphones are on the table. In short: nothing in the lineup will out-muscle it.
What Bluetooth costs you here is a little ultimate resolution, not volume.

Streaming & compatibility

 

Your phone does the streaming, so every app works — Apple Music, Tidal, Spotify, Qobuz, whatever you already use. What decides sound quality over Bluetooth is the codec, and the W4 supports the good ones: LDAC, aptX Adaptive, aptX Lossless, aptX HD, aptX, AAC and SBC. On an Android phone, LDAC or aptX pulls the most detail.
On an iPhone you're limited to AAC over Bluetooth — that's an Apple limitation, not the W4's, and it still sounds good. Want the best possible quality? Plug into your phone or laptop over USB-C and it runs as a straight wired DAC, skipping Bluetooth entirely. It clips on, or sticks to a MagSafe-compatible phone with the magnetic backplate.

Power & Battery

Two outputs, two gain levels: 125 mW from the 3.5 mm, 475 mW from the balanced 4.4 mm — comfortably more than any earphone here needs. Battery is the thing to know: the built-in 1500 mAh cell gives roughly 6 hours over Bluetooth on the 3.5 mm, and a little less on balanced or on the higher-quality codecs like LDAC.

Expect to charge it most days. Handy touch — an "Uncharge" mode lets it run off its own battery when plugged into your phone, so it powers your earphones without draining your phone.

The tech

Type: Bluetooth receiver + USB DAC/amp
DAC: dual Cirrus Logic CS43198
Amp: dual SGM8262
Bluetooth: Qualcomm QCC5181, Bluetooth 5.4
Bluetooth codecs: LDAC, aptX Adaptive, aptX Lossless, aptX HD, aptX, AAC, SBC (Snapdragon Sound)
Wired (USB DAC) support: PCM up to 32-bit/768kHz, native DSD512
Outputs: 3.5 mm single-ended + 4.4 mm balanced
Output power: 125 mW (3.5 mm) / 475 mW (4.4 mm balanced)
Output impedance: TODO — verify
Display: 2" colour touchscreen
Battery: 1500 mAh — approx. 6.3 h (3.5 mm) / 5 h (4.4 mm), continuous AAC; less on hi-res codecs
Extras: NFC pairing, USB-C (charge + data + digital input), mic for calls, "Uncharge" mode, clip + magnetic backplate
Weight: 93.3 g