As a declaimer, I'am not very experienced in the world of external DACs, therefore my view might be a bit limited. Also, the following sound impressions have been made exclusively using LDAC and a USB connection only. If connected as a USB DAC, the mode automatically switches to Performance mode, even if the Standard mode is selected. Features: Parametric EQ isn't in the app yet, but that's supposedly coming next month. Volume buttons on your IEM's cable won't work (yet). You can select the codecs from the Qudelix app, which is nice if you have one of the few aptX Adaptive devices as otherwise it prioritizes LDAC, it seems. The app has about as many features as the Radsone ES100's app, with more to come, and anyone who had the ES100 knows that it got some fantastic post-launch support. Latency: So apparently the chipset Qudelix is using doesn't support aptX Low Latency, and the USB DAC isn't working currently with the Nintendo Switch, so Switch owners, this isn't for you. aptX Adaptive's latency is fine on videos, maybe not ideal for competitive games, so I'm a bit upset that this is replacing aptX Low Latency, but it's definitely better than most other Bluetooth codecs.

The metal clip is a bit weak in terms of clamping force, so I haven't really used it. My personal opinion is that the clip should be detachable to let the entire build be even slimmer. The 5K has a neutral and balanced sound signature with a touch of the typical ES9219C treble sharpness but not to an annoyingly bright amount. I also want to clarify that I have no relationship with Qudelix, beyond the information they have provided me, so I could make this humble review. I really like the way they've designed the interaction between the wired and wireless connection as well. With my phone always connected, I can edit settings etc. on the device while having it be wired to my Macbook; i.e: you can run this device wired and wireless at the same time with minimal issue.

Warranty

The version of the APP used during the writing of this review has been v1.5 and the firmware v1.3.2. I waited patiently for a few weeks since my CIEMs were in the works. Time has passed, but nothing changed. Overall, the listening experience is very palatable with all headphones. The copious DSP options allow me to craft correction curves, which, in my opinion, make the greatest sonic improvement. I can effortlessly wrangle the Monarch’s treble peak and add the missing sparkle on the Arias. The embedded pro-grade equalizer is a vital benefit of 5K DAC/AMP over other similar products. It processes every incoming source audio from everywhere: Youtube, Apple Music, Spotify, iOS, Android, PC, Bluetooth(all Codecs), and USB.

BAND PRO GRADE EQUALIZER: The embedded pro-grade equalizer is a vital benefit of 5K DAC/AMP over other similar products. It processes every incoming source audio from everywhere: YouTube, Apple Music, Spotify, iOS, Android, PC, Bluetooth (all Codecs), and USB. For more degree of freedom, 5K DAC/AMP supports parametric EQ in addition to graphical EQ. The embedded DSP cores perform double-precision 64-bit EQ processing, providing accurate and precise frequency response.EDIT- I stand corrected- @unplugged is correct. Priority only matters when there is music playing on the BT device and USB devices. Regardless of priority settings if the USB connection is the only one live with music into the 5k- that is what will play unless you start playing on the BT connected device too. Sound Quality​Compared to the competition (BTR5), essentially the same. It's transparent, and you have full control over the filters like high-end DACs. DUAL ES9219 DAC CHIP: The ES9219 Upgraded SABRE Hifi SoC delivers audiophile-grade sound quality and output power, allowing the ES9219 to drive the most demanding headsets and provide a real line-level output to match professional audio equipment. The heart of the ES9219 ESS's award-winning SABRE DAC technology, with a Hyper Stream II modulator. This is the same architecture that is used in the world's finest audiophile equipment. I’d be lying if I said I bought the Qudelix 5K without reservation. My previous encounters with ESS chip-based DACs have been less than pleasant. I expected stringent highs and the meme “hi-end” sound that instantly wows with detail but fatigues in minutes. The equalizer is effective and processes every incoming audio from everywhere: Youtube, Apple Music, Spotify, iOS, Android, PC, Bluetooth (all Codecs), and USB.

So far, I didn't really have to plug it to a charger during the day - the battery life is more than enough, even when I travel. Connecting it to a PC for some one-hour listening session in the evening replenishes all the juice it needs. The very transparent nature of the 5K makes sure that the user is essentially listening to the sound character of the earphones and not the source itself. UNBALANCED 4VRMS: To the 3.5mm output, 5k works with single ES9219 DAC/AMP. The ES9219 SABRE HiFi SoC delivers audiophile-grade sound quality and 2VRMS output power, allowing the ES9219 to drive the most demanding headsets and provide a real line-level output to match professional audio equipment.What sets Qudelix apart is that the company is an official Sony LDAC technical partner. Reportedly Qudelix was responsible for developing the LDAC solution for the Qualcomm QCC5000 platform. The QCC5124 receiver, as seen in just about every higher-end Bluetooth DAC/amp, relies on the work done by Qudelix to operate using the LDAC codec. The Qudelix-5K has two audio outputs, one 3.5mm and one 2.5mm balanced. The 3.5mm output offers an output voltage of 1V or 2V, selectable through the APP. Using this output, the 5K works in Single DAC mode. It is very easy to use and is capable of getting the most out of the 5K, controlling the volume, output, codecs used, power supplied, sound quality... it even has a graphic and parametric equalizer, 10 bands, which works, even if the source is Bluetooth. Speaking purely of sound, the profile of the Qudelix-5K is quite neutral, I don't find it to be an amplifier, either warm, dark or overly bright. Its balance is perfect for respecting the signature of the connected headphones. In this sense, you can notice that the DACs used are SABRE, where the quality of the details and the resolution capacity are quite exposed. On the other hand, I think that the 5K is not completely analytical, but it is true that it has quite an inclination towards that profile, more than another declared soft. In my case, this type of sound is very much in line with my preferences, which is why, from the very first moment, the device has taken over most of the time, as an audio player, on my desk.