Qudelix 5K Reference DAC AMP

The review sample was kindly provided free of charge in exchange for an honest review.
I didn't receive monetary or any other kind of compensation and I don't use affiliate links.
The price of the Qudelix 5K is $109 and you can order it directly from the Qudelix website.



Qudelix 5K

The Qudelix 5K is so well known among the personal audio community and there are so many reviews floating around that I am a little embarrassed for being so late to the party.
Anyway, better late than never, let's find out more about the Qudelix 5K.



The Qudelix 5K is a thumb drive sized USB DAC dongle with internal battery and Bluetooth connectivity just like the FiiO BTR5.
The Qudelix 5K is using two pieces of the ES9219C SABRE DAC chip, for real balanced output, with an in-house written software and application.
The device has both 3.5mm and 2.5mm headphone outputs with two gain settings.
The 1V RMS mode of the 3.5mm jack offers the best power efficiency at the same sound quality as the 2V RMS mode which additionally delivers enough headroom and loudness for low sensitivity earphones.
The same principle applies to the 2.5mm output where the 2V RMS mode offers the full differential direct audio path that delivers the best linearity and separation, still with enough battery time, and the 4V RMS mode delivers the maximum output power.
For Bluetooth connectivity, the Qudelix 5K is using the latest Qualcomm QCC5124 chip which supports all the latest codec technologies, including aptX Adaptive, LDAC, AAC, aptX HD, aptX, and SBC.
To enhance the PCB reliability and durability, Qudelix are using epoxy underfills on the sensitive BGA parts, although having additional cost increase.
Those parts are bonded twice with soldering and epoxy underfills.
The Qudelix 5K uses a high sensitivity 3-dimensional LDS Antenna printed on the bottom of the case for providing the best RF reception.
The 5K also supports phone calls through the embedded high sensitivity MEMS microphone with the Qualcomm® cVc noise cancellation system.
The 5K is compatible with QX-Over which is an active digital crossover with Qudelix's proprietary DSP technology.
Qudelix 5K automatically detects the QX-Over Earphones, processes the stereo input, and outputs Stereo Low and High band independently to earphones units through 4-channel DAC/AMP.
Qudelix is very informative about the 5K design and implementation so please follow this link for an in-depth analysis.



Build quality

The Qudelix 5K is compact sized and lightweight, it measures 52.8(H) x 26.7(W) x 15.6(D) mm including the clip and weighs 25g only.
The black, rectangularly shaped, chassis is made from high quality plastic that keeps weight low but is not as durable and beautiful looking as similar devices that are made from CNC aluminum.
The side buttons are also made from semi-transparent plastic and the only metallic part is the shirt clip which is permanently attached to the main body.
At the upper part of the chassis there are located the two headphone outputs and at the bottom the USB type-C port.



Accessories

The Qudelix 5K comes packed in an environmentally friendly cardboard box and includes a USB C to C and USB C to A cables of 120mm length each.
The cables are of typical quality with a plastic sheathing and they are relatively weighty and stiff.



User interface

The Qudelix 5K is the most configurable USB DAC amp on the planet, the software allows the user to adjust pretty much anything.
You can configure the 5K either from the mobile application, which is available for Android and iOS, or the PC Chrome extension.
The mobile application works over Bluetooth and the PC application over USB connection while 5K automatically stores all the settings and reloads them at the boot-up next time.
Firmware updates are done automatically and you can configure pretty much everything, from the power output to the functions of the hardware buttons, power management and battery charging schedules, low pass DAC filter, Bluetooth in-depth settings etc.
There are so many settings that it is impossible to cover everything in the limited space of the review so you better visit the Qudelix website for an in-depth explanation of everything.



The PC Chrome extension

The Qudelix 5K is the only USB DAC dongle in the market to support a PC browser extension available for Windows, macOS and Linux and allows the user to configure the 5K when it is connected to a PC though the USB cable.
Unlike the competitive products, you don't have to use Bluetooth connectivity in order to configure the 5K while listening to music from the PC and you also have full access to the embedded equalizer which is also effective in USB mode.



Masterclass Equalizer

This is the function that differentiates the 5K from all the competition giving it a fair leap ahead, the embedded 20-Band PEQ/GEQ (64-bit double precision) pro-grade equalizer that Qudelix has developed for it.
The equalizer is effective and processes every incoming audio from everywhere: Youtube, Apple Music, Spotify, iOS, Android, PC, Bluetooth (all Codecs), and USB.
The 5K supports parametric EQ and graphical EQ with the embedded DSP cores performing double-precision 64-bit EQ processing, providing the most accurate and precise frequency response even at low-frequency range.
5K manages and stores the EQ presets in its internal flash memory and automatically reloads the settings at boot-up and resumes the same EQ setting as configured before.
So, once you configure the EQ using the app, you no longer need to launch the app to see if the EQ runs or not.
What is more is that the 5K supports the open source AutoEq project which helps users to load and apply eq presets from the AutoEq project.
The app fetches the AutoEq project data and shows them to users that have access to a database of hundreds of ready made equalizer corrections for nearly all the popular earphones and headphones of the market with a steadily increasing list.



Power output and battery duration

With 4V RMS on tap from the balanced headphone output, the Qudelix 5K can run pretty much every earphone and a lot of sensitive headphones like the Sennheiser HD660S.
The 5K is noise and EMI free with a crystal clear and silent background.
The battery duration is pretty good, depending on the power schedule, the used output and the Bluetooth codec, it can range from a whole 15-17 hours to 5-6 hours.



Listening impressions

The Qudelix 5K was burned for about 100 hours to make sure that it had fully settled down.
I have used various earphones, like the FiiO FA7S and Penon Vortex, the Sennheiser HD660S while the listening tests included both wired and Bluetooth connections.
The Qudelix 5K was updated to the latest firmware version as of 15/03/2023.



The sound is crystal clear and transparent with great source fidelity and very good technicalities.
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.
It just adds plenty of clarity and excellent detail retrieval for the category, the 5K is resolving and detailed but not analytical or too digital sounding.
The presentation is airy with a very energetic treble and an articulated mid-range while the sound is not lacking in musicality, timbre realism and naturalness.
There is plenty of energy that is adding some extra sparkle and liveliness to the sound.
This is not the most analogue and organic sounding DAC but it is certainly not lacking in harmonic wealth and tonal balance.
The bass is tight and controlled with excellent definition and layering but with a slightly lean and dry texture.
The 5K can sound very dynamic and impactful, especially from the balanced output, while it presents a well extended and spacious soundstage that is not too holographic or layered but it has an excellent positioning accuracy.
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.
So, with the choice of the right headphone the 5K can sound equally enjoyable with all kinds of music and will satisfy the most demanding of the listeners.
As an example you can choose the FiiO FH9 for a cinematic and bass shaking experience or switch to the Sennheiser HD660S for classical music listening like Yuja Wang's latest album.



Bluetooth performance

The Bluetooth connection is very stable and the implementation is actually so good that you will have to do critical listening with high resolution files and good quality earphones in order to spot the differences.
It is not that the wired connection isn't better than the Bluetooth but in most situations you will find yourself preferring the convenience of the wireless connectivity.



Compared to the FiiO BTR5 2021 ($119)

The FiiO BTR5 2021 version is the closest rival to the Qudelix 5K with the same DAC chip configuration but it uses a separate XMOS XUF208 USB receiver that allows for 384kHz/32bit, native DSD256 and MQA decoding.
The BTR5 is also using an FPGA precision clock management with dual independent crystal oscillators while it supports the same Bluetooth codecs with the Qudelix 5K.
The BTR5 has a higher quality, all aluminum chassis with front and back glass panels which give it a more premium feeling and looks but weighing 43g is heavier and bigger than the 5K which has the same size as the FiiO BTR3K.
At the front face there is a very small but useful 0.49" OLED display that allows the user to configure the menus without the need to open the FiiO control application.
The 5K has a larger capacity battery which with the aid of the various power management schedules can keep it running longer than the BTR5.



On a sidenote here is also a size comparison with the FiiO BTR7.



Sound-wise, these two sound more or less the same, you will be hard pressed to notice any audible differences - if any - well, maybe the BTR5 is a touch more refined and cleaner than the 5K.
The key difference between them is in the embedded equalizer, the BTR5 has a simple 10-band one which is only effective in Bluetooth where the 5K has the best and most configurable equalizer which is also effective in USB mode.



In the end

The Qudelix 5K might not be the most beautiful looking or premium made Bluetooth DAC/amp in the market but it stands out not only for the good sound quality but foremost for its most innovative software implementation.
It is accompanied by a great application that is available for all platforms and allows for an in-depth customization and furthermore it has embedded a PEQ/GEQ (64-bit double precision) pro-grade equalizer with additional support for the open source AutoEq project.
If you like to equalize your earphones and have full control of the DAC functionality then the Qudelix 5K is the one to have.

Test playlist

Copyright - Petros Laskis 2023.

Having become financially independent (after 6 years of uni and 1 year of internship) I finally took the plunge and requested a custom pair of IEMs. More about them later.

However, this decision entailed getting a completely new source, since my main players of choice up to then were: Sansa Clip+ and my phone (Xiaomi Mi 9T Pro).
Those wouldn't quite do, right?

So, after thinking out loud what my needs are, I realised that it'd be nice to have some device that is quite portable and can be used to enhance audio coming out of my PC, as well.
At first I thought about getting some DAP (either Shanling M0 or Fiio M5), but then I remembered that I had had a short fling with Fiio M6 and hadn't been quite satisfied with it, when it came to ease of usage and its performance (apps felt a bit laggy, the latency in DAC mode was noticeable). That's why I opted for a AMP/DAC combo.

And that's exactly how I got to know Qudelix-5K.

On paper it seemed to check all the boxes.

What's the catch? one would ask. Well.. It's availability.
At the time it was nowhere to be seen, especially in Poland, Europe.
Almost every second-hand copy sold in a matter of hours. Some eBay resellers tried to list them at 300% MSRP.

I waited patiently for a few weeks since my CIEMs were in the works. Time has passed, but nothing changed.
Finally I decided to contact Qudelix directly and ask when the next batch can be expected. Few days later I got a reply stating that it's back in stock, but at the same time they advised me to hurry, because it wasn't that big of a batch.

I didn't think twice and made the purchase almost right away.

Shipping via FedEx was quick and quite swift - it took only 7 days to get from South Korea to Poland. It's worth noting that FedEx reached out to me to correct some custom forms, but everything was sorted out when I sent them a confirmation of payment and the order summary.

Qudelix-5K was finally in my hands.
First impressions: whoah, it's really tiny! Size-wise it looks almost like my Sansa Clip+, if not a little bit narrower.

Build quality is superb. It feels very durable. No squeaks, no loose elements. The clip features a snappy spring and makes the device even more usable.
The body itself, thank God, isn't glossy. (Looking at you, Fiio BTR!) The matt finish makes the 5K quite grippy and saves it from gathering all the fingerprints.

Many reviewers have already complained about the buttons and, sadly, I have to join them, too.
I've been using it for almost two months on a daily basis, and yet - every time I want to press a button, I need to stop for a while, think, make sure it's the correct one, because it's so easy to mistake them.
It's a shame Qudelix didn't try to somehow make them differ from each other - be it in shape, placement, etc.
Having said that, clicking the buttons feels good - they are tactile and make a little sound when pressed.

When it comes to using Qudelix-5K, things couldn't be made easier.
It's just a matter of downloading a companion app to your device (even PCs have a dedicated app, which works as a Google Chrome /Chromium extension) and pairing them both together.
The app itself is quite clear and offers a lot of settings to tweak - both power- and sound-related.
The EQ tab is so extensive and so customizable that it really should satisfy everyone's needs. It definitely made my little, non-EQ head hurt.

Can't say any bad word about 5K's stability and/or performance.
When connected to my PC via USB C (I do recommend getting a magnetic plug for it, makes your life whole much easier) it immediately starts working as a main audio device. So far, I haven't experienced any glitches or anything like that. Latency is good.
It's worth mentioning that Qudelix lets you choose if you want your device to auto power on/off when connected to a charging source and that they made sure 5K draws power directly from USB when working as an USB DAC. I love that.

Bluetooth connection, especially its range and stability, also need to be praised.
I can safely roam through my home with no audio drops, even though I'm sometimes four walls away from the source.
5K communicates with my Xiaomi phone with no issues - it can control music playback and lets me answer my calls, all the while acting as a mic since the earphones I use don't have one.

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.

Re: sound quality - here's where I have to disappoint you: I need to admit I don't have much (well, almost any) experience when it comes to audio devices, especially AMPs or DACs.
That's why I don't feel qualified to say how it does on this field.

What I can tell you for sure: it definitely brings some depth and clarity to all the files I throw at it. It's unbelievable that even some 64 kbps tracks (don't ask..) had something hidden in them and Qudelix-5K made it magically reappear.

I guess that's all I had to say..

Feel free to ask me any questions!

I trialed my friend's 5K while owning BTR5, for my on-the-go pairing with my IE900. After 2 weeks of test, I decided to purchase the 5K. There's several reason why I preferred 5K over BTR5 and here's my quick review.

PACKAGING
I appreciate how Qudelix presented this. Yes, some might complain it's not as premium but heck, it save on material and shipping. I don't need wooden box, microfiber gloves and 100 pages of manual. Ok, maybe a silicon case will be great since I can't find any case for it.

HARDWARE AND DESIGN
Think of M series vs 7 series of BMW. 5K is the M series. Performance and durability first. Good plastic construction that give confident it will survive in my pocket or my bag. This thing feel like a tank without feeling overbuilt, bulky or unnecessarily heavy. The clicky buttons work well in blind without much confusion for me. Overall remind me of my old Sansa player. My previous daily driver BTR5 is thinner and longer in dimension however with case clip on, it's more bulky. Yes it's more premium and with fancy OLED but without the case, good luck not breaking it due to slippery sandwich glass construction. Come with 3.5mm and 2.5mm output but I wish it's has 4.4mm jack instead as most of my cables 4.4mm terminated. Otherwise a solid A in my book for hardware and design. I won't change one thing on the hardware.

SOUND AND POWER
This is upgrade over BTR5 for me, in term of usability, function customization and output power. The tuning is quite neutral. Great DAC implementation. The 2V over 3.5mm and 4V (!) on 2.5mm ensure nothing but electrostat will be drivable to good level. Minimal hiss on both ends too. If anyone unable to get listenable volume on the go with this device, definitely nothing else will do for you, provided you need BT function. I yet to try iFi go Blu though. BT reception seem better compared to my BTR5, no dropout at 10m unlike BTR5 which start to clip and lag. Combined with software prowess, you can adjust and adapt the hardware and sound to your liking.

SOFTWARE
Software is the one of the pillar of Qudelix 5K. Nothing come close to this app among it's peer. Buck load of customization that some might find it too overwhelming at first. Each tab come with multiple submenus for customization. Suggest to go slow and read the accompanying description on each page to understand the function. With PEQ, you can change the profile to your liking. There's also Auto-tuning function (download from database through app itself!) which is great addition for newcomer to start screwing their sound profile. Beside the sound customization, there's also lots of control over USB/BT and CODEC priority, sleep and charging behavior, battery care and over 9000 other functions. It might be too much for some but you can ignore it and it still work great.

MISC
5K has built-in mic and a great one at that. This enable voice call and even transparency mode (so-so in my experience, depend on where you clip it). I also wish it has some kind of IP water resistant rating since this is intended for on-the-go usage.

In conclusion, at around USD110, this is a solid performer among the currently available BT dongle option. Main strength are output power and software.


Qudelix 5K next to his portable home DAC/AMP, the R2R Cayin RU6. I wish Cayin have made RU6 with some kind of wireless function. That will be interesting!