Who says new technology has to mean leaving old classic designs behind? FiiO is embracing modern tech and retro design with the new KA15 USB DAC (which means digital to analogue converter), which will turn any mobile device into a high-end audio system, all within a design that givesa subtle nod to the audio tech of the past the humble cassette tape.The cassette tape design may look retro and fun, but the device isnt anything like the size of an actual cassette tape. In fact, FiiO says that its small enough to be a keyring, essentially meaning that you can take a high-quality audio converter anywhere you go. Its dimensions sit in at 65mm x 24mm x 13mm.Indeed, it is high quality. The FiiO KA15 offers dual ESS ES9038Q2M DAC chips along with a THX AAA-78 amplifier to deliver clear and rich audio with immersive dynamics. That amplifier is known for its near-zero distortion while still offering high output power, ensuring youll get clean audio that preserves dynamics without impacting overall audio response, even at lower and higher volumes. Its capable of outputting audio at up to 32-bit/768kHz PCM, and it supports native DSD512 along with MQA decoding.Despite its small size, the device has relatively versatile connectivity options. It has a USB-C input, along with a 3.5mm headphone jack, and a 4.4mm balanced output. That should allow it to work with a wide variety of different headphones. On top of that, it has three different gain settings: Low, Medium, and High. Along with a low power mode, this lets the user adjust the output based on the impedance of the headphones that theyre using. This can help preserve battery life when the DAC is being used with a mobile device. The KA15 can deliver power of up to 450mW per channel at 32.The FiiO KA15 is compatible with Android, iOS, Windows, and macOS. It comes in a variety of colors, each of which has that cassette tape design. Its available from the FiiO website for $109.