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!

After having it for nearly a week, I can say that it sounds really good to me. Of course, you have your thoughts before you have it and after you have it. I also like the fact in the app, they're very honest about the specific things it can do so that people don't get delusional. Just as it is. The app has many, many functions. Very complete app. And as they say, the quality of the music does not worsen if you lower the volume, but it stays the same, except lower.

About the EQ, DPS etc.. it has lots of pre-made sets. I tried it, but it's not to my taste. I made my own setting of EQ for my KZ ZS6 IEM (which I'll replace soon, it's already 2/3 years old) and I love how accurate the frequencies change. With a better, modern and more recent IEM I'll get even better sound, and for sure when I soon receive custom earbuds from Japan.

So the first night I've had it, I was listening to this song I used to put on, and at some point I was like: ** this bass sound so good. I was in the moment, but as like I said, with a better IEM and custom earbuds it will sound even more amazing. Also, with a balanced cable even more. I'm very enthusiastic of the future of Qudelix 5K and how they're going to improve their USB AMP DAC. I'll buy a better version if it comes out, but for now, the Qudelix 5K is a master piece.

By the way, about the button placements, I'm used to that already, because I place the device in a convenient position for myself.

I have been listening to different music genres, but mainly Rock/Kpop/RnB. I am enjoying the music even if the preset/settings of the EQ do not change. I wanted to have a setting that I can use for all music since I like music to sound more profound instead of neutral. I think that Qudelix 5K does a great job for its price, especially since its my first USB DAC AMP. I was hesitating and weighting out the pros and cons between this and BTR5, but in the end I choose Qudelix 5K and I'm not disappointed by it. As a company they've much potential and I'm glad I can support them in my way.

Build:​

First off, some photos of the device itself, and a photo of the device connected through 3.5mm to a Moondrop Aria.



It's really small and portable with a durable boxy plastic build and a metal clip. It really is the size of a 9-volt battery while being extremely light as well. A bit mind-blowing considering the performance and battery life. It's a lot smaller than the BTR5 (don't have one to compare in photographs, but it is nearly half the size).

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.

Performance + Software:​

The app is best compared to the competition IMO. It is extremely feature rich and has basically everything you need.

Battery life​

Really great. At 100% charge, I can get about 10-12 hours connected to the Arias on performance mode. Granted, I don't listen at crazy high volumes, so YMMV.

Connectivity​

Wired:​

I've been able to connect it wired to my Macbook Pro, S21, and Switch (you need to enable 16-bit for this to work) and they all work flawlessly.

Bluetooth:​

Generally pretty stable, though it is more stable over aptX than LDAC for me over longer distances.

The multipoint is pretty good generally, but it will bug out and distort if both bluetooth-connected devices start playing audio. This is especially annoying when you have a phone connected with notifications ringing - it'll destroy the quality and I tend to deselect the Q5k as an output source on my phone when this happens.

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.

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.

Parametric EQ (what you're here for):​

10 bands and very, very feature rich. It also has 20 different slots for custom EQ presets that you can make yourself. It even is compatible with AutoEQ presets which will apply seamlessly!

My one criticism is that the UI is a bit confusing and archaic. For example, there is no search functionality for AutoEQ, and it is a bit tricky to understand how to save custom EQ presets without a guide when you first do it (to do it, you press and hold on a custom EQ preset after setting up your bands).

Conclusion​

Get this even if all you have is one IEM. It is such a good value and it's so useful being able to use EQ on devices which aren't your laptop/desktop, like iPhones or Switches. It's also great to be able to simple walk away from your devices with your (presumably) high quality IEMs still connected to your ears.

These are the best bluetooth dac/amp anyone can buy right now. Everything is well thought out.

I've been using my Qudelix 5K for the past couple of months and I am thoroughly impressed. The sound quality is great, has plenty of power for IEMs but it's killer feature is the sheer amount of settings and parameters you can tweak to your heart's content. All of the functionality has been really thoughfully considered to cover almost every use case and the team behind the 5K seem to release firmware updates every few weeks with each one bringing even more useful features to the unit. The parametric EQ that works on both bluetooth and USB is one of my favourite features of this product.

As far as the build quality of the unit goes, it's a tiny smart looking and solidly put together unit. The 4 button interface is definately better than other bluetooth amps I've used in the past, the functionality of which can reprogrammed via the app to suit your preference. My only gripe is that they are a little fiddley to press because they are small.

I purchased the device with my own money and have not been paid in exchange for a review.

After reading a few impressions, and using Fiio BTR5 for more than half a year (and being so unhappy with it that I relegated it to car use, in the meantime going through some other DACs) - I decided to order the Qudelix 5k and try it - particularly after reading that it was a Sony partner when implementing LDAC (this was interesting to me considering the HORRIBLE LDAC/BT performance on the BTR5)



In order to keep this this review concise, I'm going to simply expand each Pro and Con and elaborate:

PROS:

1) Best-in-class, refined sound quality and tuning

When doing a review, it's obviously crucial to have a reference or competitor to compare. In this case, it's none other than the BTR5. I got the Fiio more than half a year ago, and although I was excited initially due to the reviews and design - I grew to almost hate it really quickly - and i've been through 2 of them already. The BIGGEST issue I had with the BTR5 was the LDAC stability. When moving more than 4-5 meters from the source, and/or when going to the gym/biking/for a jog, and keeping my smartphone in one pocket and the BTR5 in another, it would simply be unusable - constant, constant cutouts. I've tried numerous suggestions and "fixes" online, I even exchanged it thinking it was a lemon - no luck, when it comes to BT stability in many conditions, the BTR5's BT implementation is in itself a LEMON. Another 2 things I never liked about it were the sound quality and heft.
The sound always felt blunt, with minimal tuning. It doesn't have the "refined" sound one would expect from a decent DAC, even tough it was rather neutral.
The design was also quite bad - in order to clip it on a shirt, you had to use the case, which was horrible since it already made a very heavy device for it's category even heavier and bulkier. And the disappointment was aggravated by the fact that the in-built mic sounded pretty bad, much worse than an in-line mic on a cable.

Enter QUDELIX 5K. I'm happy to report that in the past week since I got it, I've had 0 (ZERO) dropouts, even when using it on the bike or at the gym - either in a separate pocket than the smartphone or on the t-shirt collar. Besides that - the sound REALLY impressed me. Just to note - I have NOT played around or modified any settings, eq, etc - I just left it standard (DAC- Performance mode - not 100% clear what that means but it's the best setting).
To compare to the BTR5 - it sound MUCH more refined, wider soundstage, better extension. I was so unhappy initially with the BTR5 that I reverted to using the jack on my phone (Sony Xperia 1 mark2 - it has dual Cirrus Logic DACs + DSEE Ultimate sound upscaling AI tech) - though the phone had less power (which didn't matter for me since I've used 2 very sensitive IEMs - Campfire Audio Polaris 2 and Dorado 2020), the sound from the phone had more heft in the lower registries and better separation (which amazed me). I ended up getting a Dragonfly Cobalt for PC use, which was closer (but a bit better) than the phone output.
As far as the QUDELIX 5k - I can say without a doubt that it sound MUCH better than the BTR5 - not a BIT but MUCH. Also, compared to my Xperia 1 II output, it also sounds wider with more headroom, and it's VERY VERY close to the Dragonfly Cobalt, which costs 2.5 times more (the Cobalt has slightly better top-end extension and separation, you have to REALLY listen to it to realise). Suffice to say, I've already sold the COBALT since I have no use for it anymore.

This is valid for both LDAC sound quality, and USB-DAC sound quality, vs the BTR5. I know some people pointed out in some reviews that on the spec sheet, the BTR5 has some dedicated USB controller. How does that help? I don't know, there's no point for a "spec" since it doesn't translate in actual performance. Same story with measurements. I turst what I hear - the BTR5 with it's advanced USB Controller does NOT sound (at all) as good and refined as the Qudelix 5K when used as a USB DAC.



2) Excellent LDAC stability, even at max bitrate (990 kb/s)

Not much to expand more here - as stated at 1), it is absolutely excellent when paired with my Sony Xperia 1 II

3) Lightweight + compact size, in-built metal clasp

This is a HUGE plus, especially over the BTR5. I can now easily clamp it to my t-shirt collar when doing sports activities, and this is all I really needed (as stated before, the BTR5 with the clasp-case was huge and very heavy). This way I can use whatever cable I want, even experiment with balanced, since I'm not forced to use a cable with in-built mic mmcx cable to be able to take calls with the BTR5 - and then when I "jailed" the BTR5 in the car stereo, in order to take calls with my phone (since Campfire Audio headphones, besides the Comet, don't come with a mic), I had to buy a new cable with in-built mic.



4) Very solid app with "transparency" mode and parametric EQ

There is not comparison with the "basic" Fiio app here. The app si excellent and lets you adjust a lot of things. 2 very crucial features, which you cannot find on many (or any?) other such companion apps for BT DACs are the Parametric EQ (I don't need it at all, but some might, it can even transform certain headphones that have issues), and the Transparency mode, AKA "Mic Pass-Thru" (which is amazing). Basically this is like any transparency mode that you can find on most NC headphones (like Sony, Bose or Apple). It lets you adjust how much sound to let through, and is VERY useful when going for a run, on the bike, or even in airports when listening for announcements (this is complemented by the fact that it's light-weight with in-built clasp and can easily be clamped to the t-shirt collar or such, even when doing sports). One small criticism here is that it doesn't seem to work if there's no music playing through the headphones - this is a small minus, and Qudelix should add the feature to always keep the transparency enabled, even if no music is playing - it can be very helpful.



5) Heaps of power for it's class, price and size

Not much to comment here - just check the specs. It has huge gusts of power (more than the BTR5). If you have smth hard to drive, this is your device. Not me though, my IEMs are quite sensitive and low-ohm.

6) Excellent Built Quality

Same here, not much to comment - even though it's plastic + metal clasp, the built quality is very SOLID. The BTR5 is also very well built.



7) Great mic quality

This is a huge + compared to the BTR5. The voice simply comes across as much cleaner and clearer, and you can even adjust it in the app. I can finally buy better cables (balanced also) and experiment without losing the call functionality like I did with the Fiio due to it's bad BT connection and mediocre MIC quality.



8) Great battery life

Simple - I get 1.5-2h more than the BTR5 on Performance + LDAC. that's around 7 hours vs 5.5 (BTR5). This is a straight forward PLUS.

CONS:

1) Buttons a bit flimsy/easy to press + weird location

It is what it is - even though the design is "cute" and the opposite red and blue led for each button looks nice (like a mini Blade Runner hover-police car), they are basically rocker buttons, and they don't have a lot of resistance when pressing - accidental presses are quite easy unfortunately. The location is also not great (on the top corners of the device...why??)

2) No display or button indicators

I personally don't care much for a display since I don't really need to look at it (and eats a bit of battery), but this is simply a feature that is absent on the Qudelix, but is present on the BTR5. Also, it has no button indicators at all.

3) Not water-proof in any way

This is not really a FAIR minus (no other device has IPX rating either, in this category, at least as far as I know) - but considering one of my use cases is doing sports with the Qudelix attached to the t-shirt collar, it gets touched by sweat from time to time, and sweat-proof rating would be a huge addition for reliability and longevity.

4) Although the packaging is nice and unique, a more premium unbox experience would go a long way for brand-awareness

I mean...look at it ) Check more online photos. Yes, there is some innovation there as it's sort of a origami-type technique to make the box so small, it doesn't really scream "cheap" - but having a much nicer box with some extras inside is what many people enjoy when getting a new device and unboxing it, it makes the experience memorable, and it's a very useful marketing tool for companies that want to build customer retention.
It can be argued that this is cost-cutting decision, and it can be justified, considering the device cost is in-line with the Chinese counterparts, but this is built in Korea (higher production costs). But considering the advantages, I think asking for 10% usd extra and shipping it with a premium box would go a long way and would help Qudelix more in the long-run.

5) OTA software update has some issues

This is something that needs to be fixed URGENTLY by Qudelix. Basically, in order to not have a FAILED update, you need to keep the screen open and the app in the foreground during the entire process. Switching out of the app or letting the phone go into idle mode (screen off) instantly freezes the update process, and you need to either repair or reinstall the app. Frustrating. On the other hand, it's not a minus vs it's direct competitior, the BTR5 - that one has no OTA update (as of yet) and needs to be updated in a very "oldschool" manner using a PC, and that also means you need to check the support page on the FIIO website from time to time to even KNOW if there's a new update. The Qudelix app instantly notifies you when there's an update.

6) No way to configure buttons and no way to access smartphone Assistant (Google Assistant/Siri/etc)

I consider this a big functionality omission by Qudelix. Almost every other product in this category (BTR5 included) has a way to map a button to be used as the Assistant activation in order to easily call someone when doing other activities (for example). NO such option on the Qudelix, you can't even re-map the buttons. I really hope this can be added in a future SW update - QUDELIX - PLEASE ADD ASSISTANT BUTTON MAPPING OPTION! 10X!

And that pretty much wraps my review. For reference, this is the gear I've used in this comparison/review process:

Sources: Laptop (USB) and Sony Xperia 1 mark2 (LDAC BT)
DACs: Qudelix 5K (duh!), Fiio BTR5, Audioquest Dragonfly Cobalt (sold)
Headphones: Campfire Audio Dorado 2020 (main), Campfire Audio Polaris 2 (for sale), Sony XBA-N1AP (sold)

Introduction
Qudelix is a new American company, set up by the former lead engineer of the now famous Earstudio ES100. The Qudelix 5K is a new Bluetooth DAC amp, featuring the new CSR8675 BT receiver, one of its main advantages over its competitors, such as the Fiio BTR5 and Shanling UP4. Otherwise, the three feature the same dual ES9218P DACs, balanced and unbalanced ports and a USB-C port, as well as app support. All this can be had for $109.

Package
The Q5k comes in a very simple cardboard box, which includes the BT device, USB-C to USB-C and a USB-C to USB-C cable, as well as some paperwork. The unboxiing experience is simple, but gets the job done 6/10.

Built
The Q5k is made of mainly dark, hard plastic, with only the clip and skrews being made of metal. It feels very solid, but at the same time quite light, lighter than it looks. The whole device is tiny, smaller than the relatively big UP4 and still smaller (by volume) than the BTR5. Considering they have nearly the same specs, this is really quite impressive.

The one downside to the build is that it is made of plastic, as a result it simply doesn't feel as premium as the glass and metal sandwiches of the BTR5 and UP4. I personally wouldn't mind a slightly higher weight, in return for a more premium feeling build, but I do understand the decision. Also, the one aspect that is made of metal, the clip, is non-removable. To me, it feels very solid, like the rest of the build, with good strength, but it could become a problem to replace if broken. Overall, although maybe the not most premium feeling device, it is solid and I have little worries in its long-term durability, therefore it gets a 8/10.

Controls
The device features 4 buttons in total, two on each side. The ones on the right feature a blue light underneath, while the ones on the left have a red light. The light intensity, or when or even if the lights turn on, can be customised to your preference in the app, and so can the functions of the buttons. You can choose which buttons turn on/off the device, skip and go back on tracks and turn up/down the volume, essentially everything you would want. As a result, the controls are very comprehensive and warrant a 8/10 rating, the only real downside again being the plastic build, which include the buttons, as a result the controls are not as tactile as the ones on the BTR5.


Bluetooth Connection
Not much to say here. The device features Bluetooth 5.0 with the newest Bluetooth processor, which supports practically all Bluetooth codecs available. The connection occurs automatically once turned on, and is rock solid once connected, with no hiccups. I've had absolutely to issues with its Bluetooth connection 10/10

Sound
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.

The Q5k features a 3.5mm unbalanced and a 2.5mm balanced port. They feature a 2.0 Vrms and 4.0 Vrms power output respectively, meaning it is powerful enough to drive just about any IEM on the balanced port, the same as the BTR5 and UP4.

The sound coming out of the device is of very good quality, especially for a Bluetooth device. It is quite neutral, from bass to treble, with just a slight lift on both ends. It's neither warm nor cold and note thickness is neutral as well. There are multiple minor improvements in sound quality, overall improving the SQ a great deal from a simple smartphone.

To start of with, the bass gets a very slight lift, but the main improvement is in speed and impact, which improve quite significantly. The mids remain quite uncolored and experience probably the least change from the overall sound signature. The treble also features a slight lift in quantity, improving resolving power and adding a but more spice to the sound of your IEM, although not by much. Lastly, soundstage improves quite substantially in all dimensions. Width and depth improve and so does imaging and layering, leading to a more detailed and more engaging soundscape. All these little changes lead to a greatly improved sound, compared to a smartphone. There is further improvement to the sound in all aspects, athough very minor, when connected through the USB port. Overall, this is as good as a Bluetooth receiver will sound at this price 10/10. I've also experienced to hiss through the device, although I haven't used it with a pair of particularly sensitive IEMs.

App
This is really the main advantage of the Qudelix compared to its competitors. The app is quite simply fantastic. It has all of the features a user would ever want, including an excellent parametric equalizer. The app is very well done, with a great user interface, and includes things like a battery graph, volume controls, Bluetooth codec selection DAC/AMP mode, DAC filters, output power and even days under warranty remaing. It is miles ahead of what Fiio or Shanling offer and still gets regular updates.

I have to specially mention the PEQ. It is really good quite simply. Its a 10 band one, which can be either parametric or geometric. It changes the sound very effectively, with little effect on overall sound quality. There are now custom presets that can be used by the user, on top of some pre-made ones. All in all, this might be the biggest reason to get the Qudelix over the Fiio or Shanling. The app gets a straight 10/10 for this.
Battery
The battery life is actually surprisingly good for such a small device, claiming actually to be better than both the UP4 and BTR5. It has a claimed 6-20 hour battery life (depending on volume and power mode. It usually lasts me about 2 weeks of usage with about 1-2 hours of listening per day. It is charged through the USB-C port, and can be used while charging, which is a really nice feature to have. The app also features a battery graph, which is a nice touch.
Conclusion
To sum up, the Qudelix 5k is a fantastic device. There's very little wrong with it. It has a fabulous app, great sound, good built and very good battery life. Compared to the Shanling UP4 and Fiio BTR5, it's smaller, with better Bluetooth connection. To me, this is a absolute no-brainer, if you are in the market for a BT DAC amp. The only real downside for me is just how similar all these BT devices are, but I believe the app on the Qudelix really makes it worth the extra 10-20$ over the latter two. This is as good of a small BT portable amp you can get.

Thank you for reading all the way down here : ) This my one of my first review ever and would highly value any feedback given and I hope that you have enjoyed this review. Also, if any company also enjoyed this review, and would wish to send me some gear to review, I would be delighted to do so.

The 5K has a compact design with a very rectangular shape. It is made entirely of plastic, main body and buttons, with the exception of the attached fixed clip which is made of metal. The plastic material can make it look plain but it is well built and seems solid enough. While an aluminum body could be tougher and more durable, for the better wireless signal the option is either plastic or glass. Glass may be nicer but more fragile and easier to catch fingertips. The clip is strong enough, though I’d preferred it was removable. There is no official case for the 5K but Dignis had already made one.


The layout is pretty simple, well distributed but not the most comfortable. There is a rocker button on each side of the device. Their defaults functions are described on the box, but can be changed from the app settings. I found them logical enough so didn’t mind anyway.


The right side buttons work for power on/off, playback, Bluetooth pairing and managing calls. The left button is for volume control. Below are the functions of each one by default.


Having separated controls for volume and playback is very comfortable. You can press and hold the volume and smoothly adjust it thanks to the up to 120 volume steps and slight increase of 0.5db each. The Fiio BTR3K and BTR5 are more annoying as the same rocker button works for volume and skipping tracks, where you need to make multiple single clicks to change the volume and hold to skip tracks.

There are LED lights under each button that (by default) turn on whenever the buttons are pressed or when pairing the device; blue to the right and red to the left.



The buttons are too sensitive and they are placed exactly opposite to each other, so when pressing one side the other’s side button can be easily pressed. It is not very annoying but needs some time to get used to.

At the upper side are the two audio outputs, single 3.5mm and balanced 2.5mm. To the opposite side there is the USB Type-C socket for charging or for wired DAC use.


There is an issue to note regarding the audio outputs. When using the 2.5mm and then switching to another headphone on the 3.5mm port, the sound will be unbalanced and distorted. The only way to fix it that I found is to turn off the 5K and reconnect it again. This may not happen all of the time but most of it. I’m not sure if it is a particular problem on the unit I received or not, though it seems to be because the device tries to continue to output as in balanced sound mode and does not change back to single-ended.


Software

Like other portable Bluetooth amp/dac devices, Qudelix also offer an application for Android and iOS devices. I don’t own any modern iOS, but with Android it is limited to be used with only 8.0 and higher versions. Well, it was released in 2020 and it is supposed to be used mainly with smartphones so they expect that everyone should own an updated one. Moreover, if you want the best wireless audio quality you’d want a phone that supports LDAC or at least AptX/HD.

The app shows all the technical info about the 5K device, battery time and performance, firmware details and even remaining warranty period. There are various screens that can be accessed by the corresponding icons at the bottom bar, each for a different hardware or software configuration. There is a short description of the many features on each screen. Both the source device and 5K volume can be controlled by the app, as well as changing the buttons’ functions, volume limit, codec, output power and sound quality performance.

A more interesting and probably the most useful feature should be the equalization section. Good news is that all the EQ options can work over BT, including LDAC, and also when used as wired USB DAC. All the configuration and EQ are saved into the flash memory of the 5K so will remain the same when connected to other devices. The EQ is offered in two flavors: Graphic (GEQ) and Parametric (PEQ). On the Graphic EQ are some included presets and 20 extra Custom slots that can be user defined. The Parametric EQ is always much more complex and requires some knowledge and time to use but allows a more precise customization of the sound.

The app performance may depend on the device, and from a Samsung Galaxy Tab with updated Android 8, the app is very stable. Also Qudelix keep releasing updates with high frequency (compared to other companies), and the app is already fairly usable since the recent release of the 5K.


Bluetooth quality

The main purpose for the 5K is to be used as a wireless audio receiver, and Qudelix suggest it is better used with smartphones (Android 8+ or iOS) than with other Bluetooth supporting devices (PC, non-Android audio players, etc.). In fact, the wireless connectivity turns out to be better when used from Android 8+ devices and even more when the app is working. With the Galaxy Tab connectivity is very stable and the wireless range is very good even with a couple of walls in the way, even with LDAC codec on.

Battery

The battery performance is very good on the 5K. It is advertised as able to play up to 20 hours, but of course it will depend on the BT codec, volume level, audio output and audio performance set on the app. Using IEMs and earbuds it easily plays to more than 10h in higher performance and 2.5mm balanced, so the numbers seem rather accurate, and anyway is the best battery time among other BT receivers.


Sound Impressions

The Qudelix 5K follows similar sound characteristics to most of the compact portable sources I’ve tried at this price range. Regardless of their purpose or inner hardware components, from audio players, wired or wireless USB amp/DAC, they tend to present a more or less neutral and uncolored sound. There are always differences in their final tuning when compared to each other, but none of them put much coloration to the sound or go overboard sounding too warm or too bright.

Sound quality on the 5K is very positive. Without using any EQ it is clear, very neutral and clean, presenting no hiss with the more picky sensitive IEMs I could try. The very wide volume range of 120 steps allows a perfectly accurate and comfortable listening with very low impedance IEMs, usually multi-BA or hybrids, and can also get loud enough with more demanding sets without showing major signs of distortion. It can drive IEMs like the final E5000, B1 and Dita Twins with more than decent power, and also 120ohm earbuds, on-ear headphones like SM P55 Vento, and if you insist, the new iBasso SR2 will sound decent enough for such a small device; not my choice, though.

Despite the very neutral signal, there is a very slight sense of warmth to sound that gives a more natural texture. While the low-end is nothing elevated, when using the DK-3001 Pro and Dita Fidelity which are very neutral their bass they gain more body and little more solid impact and decay, and even the 3-BA Fibae 3 sounds less bass light. The midrange is very clear, not particularly airy or open, but less congested or artificial than with the BTR3K/M5 or Shanling M0. The treble quality is particularly good on the 5K. Detailed, clean and fairly natural and a bit smooth, and very good for a BT device. A bit surprising from what I’d expected from a Sabre DAC at this price and compared to the other Sabre based sources where the treble has more brightness and is less forgiving. There are still the usual limitations in terms of average soundstage and extension, but it is acceptable for the price and especially being wireless quality, and the more natural timbre and tonality the 5K presents as a sub $200 source makes up for its limitations.

While the single output works with only one DAC chip, switching to the balanced output takes advantage of the dual Sabre DAC. When changing to the balanced option there is a jump in output power that is clearly audible in the louder volume of around 8dB which translates into ~15 steps in the 5K device volume scale. The overall sound presentation remains unchanged but it is a bit better, more open, with more air and sense of space, especially noticed in the treble response. Not a must but worth using if you already have the setup for it and don’t mind the faster battery drain.

Introduction

Qudelix, as highlighted on its website, is an audio systems engineering company, based in Seoul, Korea. They are also a technical partner of Sony LDAC™. They have developed the LDAC solution for the Qualcomm QCC512X platform, which is one of the best chips for audio playback via Bluetooth. This platform, besides offering the best quality codec for Bluetooth audio, has an ultra low power consumption. On the other hand, it has a powerful DSP, capable of maintaining a high bitrate during transmission, in a safer way and for longer. As a result of this effort, Qudelix provides such LDAC codec solution to other brands and/or headphone manufacturers.

All this technical capacity has resulted in one of the most interesting devices on the portable Hi-End market, which combines the best Bluetooth option, with an excellent Dual DAC/AMP by SABRE (ES9218P) and a high output power. This is the Qudelix-5K: a small Bluetooth receiver of very high quality and a DAC/AMP. It can be used as a sound card, connected to a PC or laptop. It can also be connected, via Bluetooth, to a Smartphone or DAP, to be used as a Bluetooth receiver and headphone amplifier. Finally, it can also be connected, via USB-C, to a Smartphone or DAP, to be used as an amplifier. It even has a high-sensitivity microphone as a Bluetooth communication solution.

It has 3.5mm (80mW to 32Ω) and balanced 2.5mm (240mW to 32Ω) outputs.

Another great advantage of this small device (it only weighs 25g) is that it can be governed, completely, by way of an attractive APP, which can be downloaded from the official Google and Apple shops:

https://play.google.com/store/apps/details?id=com.qudelix.qudelix&hl=en_US

https://apps.apple.com/kr/app/qudelix/id1515641059?l=en

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.

In the present review, I'm going to go through all the details of this versatile and very complete product.



Disclaimer

I want to thank Qudelix and especially the support staff for giving me the opportunity to try this product.
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.

Specifications

• Maximum output power 3.5mm Unbalanced: 2.0V RMS (80mW per channel)
• Maximum output power 2.5mm balanced output: 4.0V RMS (240mW per channel)
• SNR (A-weighted): 3.5mm -118dB. 2.5mm -122dB
• THD+N: 3.5mm 0.004%. 2.5mm 0.002%.
• Separation: 3.5mm 79dB. 2.5mm 117dB (1kHz/32Ω).
• Output impedance: <1Ω.
• Bluetooth: 5.0 Class 2 (25mW 4dBm) up to 10m. 2.4Ghz.
• Bluetooth chip: Qualcomm QCC5124
• DAC: Dual ES9218P SABRE HiFi®. The 3.5mm output works in single DAC, only. Dual DAC is only available for 2.5mm output.
• Bluetooth Codecs: aptX Adaptive, LDAC, AAC, aptX-HD, aptX, SBC
• Battery life: 6 to 20 hours (500mA Battery)
• Use as USB DAC: maximum resolution 96KHz/24-bit
• Double Precision 10 Band Equalizer PEQ/GEQ
• LDS (Laser Direct Structuring) antenna, high sensitivity and 3 dimensions.
• Technology used for noise cancellation: Qualcomm® cVc™
• Microphone: High sensitivity MEMS.
• Firmware update via Over-the-Air (OTA).
• Complementary mobile application iOS/Android.

User Guides

https://drive.google.com/file/d/1Z7sMD4v_8P1zYGW7-hrHvHVJRdm-3bQA
https://drive.google.com/file/d/1LD4-w-bbJv3y0XpQjvOh6iaw2bcp_O61



Packaging

Surprisingly, the Qudelix-5k comes in a small, unpainted, pure cardboard box. Its dimensions are 91x55x55mm. It is sealed with two transparent stickers, on the top and bottom. On the different sides of the box, there are different notes on the product. On the upper side is the brand name, logo, slogan, where it was manufactured (Korea) and the different guarantee certificates. On the lower side there is an EAN13 code. On the other sides, there are drawings of each side of the product, explaining its basic functions, as a quick guide.

After opening the box, on the upper side, you can see the DAC, wrapped in a bubble bag, located in an area adjusted to its size. If you open it from the bottom, you will find a zip bag containing two black cables. One is a USB-C to USB-C type and the other is a USB to USB-C type. They are all male. The full length, including connectors, of each one is approximately 150mm. And that's it, no instruction manual or warranty card is included. On the other hand, the user's manual and the operation note, can be downloaded through the APP or with the existing links on their website (which I have previously linked). These documents are very complete and excellently explained.

The guarantee is for one year and their condition can be checked through the APP.

The content, as you can see, is the minimum required. The packaging feels like an industrial, rather than a commercial product. However, it does not cease to have its charm. The box and its design, through a single sheet of untreated cardboard, its drawings in black ink and its schematic explanations, give an idea of a different product, where the effort is inside and not in other less superfluous things. In any case, I like very much, that austere, simple but ingenious presentation and so reduced in size.



Construction and Design

The Qudelix-5K is a small regular parallelepiped, measuring 52.8x26.7x15.6mm. Its weight is 25g. Its body is made of very hard black plastic. It also has an anti-scratch UV coating. It has a dark grey aluminium clip at its base. On it are written, in white ink, the model, where it has been manufactured, as well as the different certifications that it complies with. In a vertical position, on the upper face, the one that is closest to the clamp's ball joint, are the audio outputs, 3.5mm and 2.5mm (balanced), as well as a hole for the microphone. On the opposite side is the USB-C connection. On the left side, there is a button with a double function: if you press on its top, the volume increases. After pressing the lower part, it is lowered. It is translucent and lights up in red with each press. On the left side, there is another button, with the difference that it has a bulge at the top, to make it easier to identify by touch. On this occasion, its light is blue. Pressing the upper part for 3 seconds, you enter Bluetooth pairing mode. Pressing the bottom part, also for 3 seconds, turns it off or on, as appropriate. Finally, at the base of the front panel, you can read "qudelix" in inscribed letters.

Despite the fact that the body is made of plastic, with the exception of the clamp, its high rigidity gives a rather hard feeling. Even, with the paint, it seems that its body is completely metallic.

Its construction is extremely compact, only two screws can be seen on the face where the USB connection is. Although, it is possible to see the slots and joints, these are either very small or are very well assembled and do not offer any sensation of weakness. Despite the simplicity of the form, the device has a very effective and functional design, more than striking or spectacular. Above all, its small size, weight (I repeat, 25g), as well as its efficient ergonomics and ease of use, stand out.



Connectivity

The 5K has two basic functions:

First, as a Bluetooth receiver/headset amplifier: in this case it will be necessary to connect to a Bluetooth source. The audio codecs used are SBC, AAC, aptX, aptX HD, aptX Adaptive and Sony LDAC™. In this regard, it should be noted that Qudelix, is Sony's LDAC "Official Technical Partner" and has developed the LDAC solution for Qualcomm's QCC512x platform, which is a best-in-class SoC for high-end Bluetooth applications. The QCC512x's ultra-low power consumption and more powerful DSP capability allows application devices to maintain a more secure, high-bit-rate LDAC stream for longer. All this information is explained in detail on the brand's own website. It should be noted, of course, that the 5K is the first LDAC receiver to display the active LDAC bit rate.

Second, as a USB DAC/headphone amplifier: the 5K can be connected, via the built-in USB cables, to a PC, a smartphone or a DAP with a compatible USB-C output. In this connection mode, the 5K supports the following sampling rates: 44.1/48/88.2/96kHz. Using the APP, you can choose a single rate or all of them. The bit depth is 24.

Connected to a PC, no drivers are required. For configuration, e.g. with Foobar2000, it will be necessary to choose the "WASAPI" (push) or (event) output and 24-bit. It can also be used with ASIO4ALL.

When connected to a smartphone, it is necessary to choose, in the playback APP, that the audio output be through the Qudelix-5K.

It should be noted that both connections can be established at the same time. The 5K can be connected to the Smartphone, either via Bluetooth or USB. The audio source can be chosen at any time via the playback APP or the Smartphone itself. When this is chosen, it becomes exclusive.

It can also be connected via Bluetooth, through the Smartphone and connected as a USB DAC to a PC. In this case, the Bluetooth source is the main source and the USB DAC connection is the secondary source. Simply by pausing one source and resuming the other, it is sufficient to switch the audio from each source.

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.

The 2.5mm output offers 2V or 4V, also selectable through the APP. If this output is used, the 5K offers its best technical virtues, as it uses the Dual DAC configuration.

When the high power output is selected, the volume is not increased, but extended to +6dB, instead of 0dB.

The 5K has two profiles or modes: Standard or Performance. The Standard mode provides the best balance between sound quality and battery consumption. Basically, this mode uses the standard operating clock of the DAC and the standard output bias current. The Performance mode gives priority to sound quality as opposed to battery consumption, which may be shorter. In this case, the DAC clock works in its maximum position and the bias current is also the highest.

If connected as a USB DAC, the mode automatically switches to Performance mode, even if the Standard mode is selected.



Operativity

The Qudelix-5K is an extremely versatile product. In addition to the above, connected via Bluetooth to the Smartphone, the high-sensitivity MEMS microphone can be used, which is built in. In this way, it is not necessary for the connected headphones to have a microphone. However, by means of the APP, it is possible to select the use of one or the other, including the sensitivity level, if the 5K microphone is used.

The operation of the 5k, is quite simple, it has 4 buttons, grouped one on each side, under a transparent casing. Each of them has an LED: blue for the right side (which also has a protruding mark on the top), red for the left. As a quick summary, their functionalities are:

Upper blue button:

• Pairing mode (long press 3 seconds)
• Play/pause (one click).
• Next song (double click).
• Answer incoming call (one click)

Lower blue button:

• On/off (long press 3 seconds).
• Previous song (double click).

Upper red button:

• Volume up (+0.5dB)

Lower red button:

• Volume down (-0.5dB)

To pair the 5K via Bluetooth, simply turn on the device and enter pairing mode. At this point, the red light and the blue light come on alternately to indicate this status. It is recommended that LDAC mode is chosen from the Smartphone, for maximum sound quality.

It is also possible, from the development options, in Android, to select the LDAC bitrate. The 990kbps/909kbps, 660kbps/606kbps, 330kbps/303kbps modes as well as the adaptive bitrate mode are supported and can be used. Even the used bitrate can be displayed from the APP.

The Bluetooth range is up to 10m.

The volume has an option, called "Absolute volume", which allows total control of the volume, both of the source (Smartphone) and of the 5K. This allows for fine adjustment and the best possible sound quality. The sound jumps of the device are measured in 0.5dB, obtaining a very high precision, as well as being simple to operate. The maximum volume is 0dB, but when the high gain is set, the maximum is +6dB, which means doubling the amount of volume.

The 5K, on the other hand, has a high volume protection, which protects the connected headphones, when switching between different audio sources. If the volume differences between them are too great, the system adjusts the volume as a protective measure.

The APP can also be used to limit the maximum volume as well as the volume of each channel.

As is usual with many DACs, it is possible to select between different filters. They are as follows:

• Linear phase fast roll-off.
• Linear phase slow roll-off.
• Minimum phase fast roll-off.
• Minimum phase slow roll-off.
• Apodizing fast roll-off type 1.
• Apodizing fast roll-off type 2.
• Hybrid fast roll-off.
• Brick Wall.

They can be chosen from the PPP and there are explanatory charts for each one.

The 5K has a 10-band equalizer. Thanks to the use of the QCC5124, which is the neurological centre of the device, it is possible to use such advanced audio processing. Inside is a 32-bit dual-core KALIMBA DSP, which runs at 120MHz. The use of the equalizer is independent of the source used, whether Bluetooth or USB.

The equalizer can be used parametrically (PEQ) or graphically (GEQ). Its equalisation processing is 64bits, with double precision.

It has a large number of pre-set presets and up to 10 individual presets can be saved. All of them are stored in the device's flash memory.

It should be noted that the current status of the device is also stored in the internal memory and when it is switched on again, the system remembers this status.

The battery of the 5K, is 500mA, from Li-Polymer. Only a current of 200mA is required to charge it, a current which limits the device itself. This means that the entire charge takes 2.5 hours (pure and simple mathematics). The included battery charger can be activated at will, except when the battery charge is less than 20%, in which case it will be activated automatically, provided it is connected to a USB.

Connected as a USB DAC, the device uses 200mA for charging, if enabled, and 300mA for operation.

The power mode can be configured, among 4 options: Do nothing, turn on when connected as USB DAC, turn off when charging or turn on or off depending on whether or not it is connected to the charger. All these options can be chosen from the APP.

The battery life can vary between 6.71 hours (Performance mode, Balanced 4V LDAC 96kHz @990kbps) and 20 hours (Standard mode, Unbalanced 1V AAC 44.1kHz) depending on the tests performed in the laboratory.

As usual, the battery life will depend on each individual use, the volume used, the mode, the gain, the codec used and the transfer rate.

My experience of use, based on 70% connected as a USB DAC with the charger switched off and 30% via Bluetooth or connected to a DAP or Smartphone, via USB-C, is that the battery life is, practically, as the tests promise. After two weeks of daily use (1 to 4 hours a day), I have reached 20% battery life. It's true that the connected headphones have been low impedance IEMS or low or medium impedance earbuds. I have alternated use, both by balanced and unbalanced output, switching between high and low gain. In addition, the 5K can be connected to the PC as a USB DAC and when not in use the battery consumption is minimal.

Finally, from the APP, there is a specific section to monitor the use of the battery.



APP

As I have already insisted, the use of the Qudelix-5K is extremely simple. And the maturity of the APP makes it very easy to have absolute control of the device, and also provides a lot of information: help, links to manuals, to the forum, technical support, warranty management... It also allows the firmware to be updated, through OTA.

The version of the APP used during the writing of this review has been v1.5 and the firmware v1.3.2.

The APP works very smoothly and I have not detected any hang ups or abnormal functioning.

It has 5 large sections and within each section, there are several sub-sections. In summary, the distribution would be something like this:


In addition to the options, each screen has detailed information about each of them.

Personally, I love the theme with black background used, with the text in a soft white and the options selected in red.

One of the most interesting things about this device is its multifunction: it can be connected to the PC at the same time, via USB, as a DAC and connected to the Smartphone, via Bluetooth. All this, while having complete control, by means of the APP. You can listen to music via the smartphone, pause playback and resume playback on the PC, without having to touch the device or the APP at all.

To go into detail about the functioning of the PPP would be excessive for this review. So I prefer to put screenshots of practically all the screens, grouped in groups of 4 screenshots per image. The text is completely in English.

But I would like to mention some virtues and/or curiosities, related to the PPP and the configuration of the device:

• The operation of the buttons can be programmed, offering alternatives of use to the pre-set one.
• You can control the activation of the 5K microphone, as well as its gain level or choose to use the headset microphone.
• It has a guarantee control, specifying the days remaining until the end of the period.
• You can choose how the device works, when connected as a USB DAC or to a charger.
• You can control the volume of the Smartphone, the device and display the Bluetooth codec being used, as well as its bitrate and transfer speed.
• The equalizer can be used even if the selected source is Bluetooth.

Measures

All measures have been taken with the Performance option activated. The voltage measurements are RMS.

In the following table the 3.5mm output voltage has been measured (selecting the "Normal" or "High" option) with a digital multimeter, using a sine wave of 100Hz and amplitude 1, in FLAC 870kbps to 96kHz.


In the following table the voltage of the 2.5mm balanced output has been measured (selecting the option "Normal" or "High") with a digital multimeter, using a sine wave of 100Hz and amplitude 1, in FLAC 870kbps to 96kHz.


It can be seen that, at 32Ω, the output voltage does not reach the maximum. It is possible that at low impedance, the amplifier will reach current saturation. It should be remembered that, in the specifications, the maximum power is:

• 3.5mm: 80mW.
• 2.5mm: 240mW.

In order to visualize the pure waves, reproduced by the 5K, I used the oscilloscope.

The 3.5mm output, connected to 32Ω at 0dB volume, offers a slight saturation, at 1.06V.



The 3.5mm output, connected to 32Ω at -0.5dB volume, is unsaturated, at 1V. This means a power of 31.25mW.



The 3.5mm output, connected to 32Ω at 6dB volume, offers visible saturation, at 2.07V.



The 3.5mm output, connected to 32Ω at 5dB volume, has no saturation, at 1.85V. This indicates that the power of the unbalanced output is 110mW, higher than the 80mW declared. The current required to obtain this power is 57mA.



The 3.5mm output, connected to 100Ω at 6dB volume, does not present saturation, at 2.1V. The power measured at this point is 44.1mW.



The 2.5mm output, connected to 32Ω at 0dB volume, has a clear saturation, at 1.79V.



The 2.5mm output, connected to 32Ω at -2dB volume, has no saturation, at 1.68V. The power at this point is 88.2mW.



The 2.5mm output connected to 32Ω at 6dB volume, has a clear saturation at 3.22V.



The 2.5mm output, connected to 32Ω at 3dB volume, provides a clean signal, at 2.92V. The power measured at this point is 270mW, which is more than the 240mW declared. The current in this case is 91mA.



The 2.5mm output, connected to 100Ω at 0dB volume, has no saturation, at 2.14V.



The 2.5mm output, connected to 100Ω at 6dB volume, has no saturation, at 4.13mW, and the power is 170mW.



It can be seen, then, in spite of the visual measurements, that the Qudelix-5K, for the 3.5mm output, at 32Ω, offers more power than stated (110mW), clearly exceeding the 80mW indicated in the specifications.

Something similar happens with the 2.5mm output, capable of reaching 270mW, for 32Ω, which is a great power figure, higher than the 240mW declared.

In the following picture you can see the frequency response, from 5Hz to 40kHz. You can see that the response is completely flat, from 20Hz to 30kHz:



Finally, below are the measurements taken with the oscilloscope, without load, making a frequency scan, from 20Hz to 20kHz, using the maximum volume (0db and 6dB), for both outputs.

3.5mm Output at 1V:




3.5mm Output at 2V:




2.5mm Output at 2V:




2.5mm Output at 4V:




Sound

Thanks to the ability to connect to multiple sources at once (Bluetooth and USB DAC), it is easy to switch quickly between them, just by pausing one and resuming the other. In this way it is very easy to make comparisons between the two connections. The fundamental conclusion is that there are hardly any differences between the two sources. With medium or low range headphones and MP3 files at 320 Kbps, I would dare to say that the differences are almost indistinguishable. If I were to carry out blind tests, playing the same files, I don't think I would be able to distinguish either the differences or the origin of the source. This is something that has really surprised me. With the Qudelix-5K it is no longer necessary to have a DAP, if our Smartphone has LDAC and a sampling rate of 660kbps, or more, it is totally sufficient. And it doesn't matter if it has been tested for the 3.5mm or the 2.5mm output.

To find some differences you would have to go to great files, very well recorded music and use the best headphones you have. But even so, the results are very similar, bearing in mind the limitation that, by USB, you can only play files of up to 96kHz (a value which, on the other hand, is quite high). My feeling is that, via USB, there is a greater sense of dynamics and that the recreation of the scene is more rounded, with greater depth and three-dimensional effect. But the extraction of detail and the presentation of the sound are really on a par.

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.

The reproduction of the lower area is perceived as extremely clean, very well shaped, with a good resolution drawing, but without too much roughness, showing that more analytical and defined presentation. The depth is good and the separation of planes is on a par. But, really, it is not an amplifier that enhances the bass or gives it a higher weight than other bands. The balance it has is very noticeable, as well as the respect for executing the area with greater resolution, allowing its background to be quite clean and airy, achieving a fairly decongested and luminous sound.

These qualities benefit greatly from the needs of the mid-range. I do not understand that the 5K is a mid-center amplifier, but its characteristics are capable of enhancing the details and nuances of both the voices and the instruments. Its dark background, above all because it is balanced, gives great dynamics to the sound, as well as definition, transparency and quite high resolution capacity. Thus, the voices appear very natural and very well defined, accompanied by the perfect distance, between the accompanying instruments.

I find that one of the best qualities of the 5K is the respect it has for the sound of the connected headphones. It is very capable of extracting many of the virtues of each one of them, but in a very natural way, without the sound feeling forced or artificial. Its high resolution capacity offers a calm listening. Its level of definition does not overwhelm at all. And a good reason for this is the treatment it offers to the treble, drawing them very well exposed, thin, sharp, brilliant, but docile, with a definition at the height of the neutrality offered, accompanied by a large dose of air and separation. From this, we obtain that declared analytic character and its level of separation, which, in sum, is capable of generating a scene of appreciable width, remarkable depth and adequate height. The level of three-dimensionality is not very high, since the stage is observed from the front. But, in this way, the scene persists naturally, escaping any forced unreality.



Comparisons

Sabaj DA3, Tempotec Serenade iDSD

A three-way comparison between different devices, but of the same price, may be somewhat inconsistent. But, speaking purely of sound, it is totally justified.

Used, all, as USB DACs, the profiles differ between the iDSD and the 5K and DA3. The first is eminently warm, while the other two are more neutral.

Continuing with iDSD, it has the darkest sound of the three, with a more subtle brightness, where details are less exposed. Its sound feels more congested and cohesive, less clean.

The DA3 is harder, its edges are sharper, it's almost the opposite of iDSD. It doesn't have its softness, nor is it as wide, which enhances the feeling of a sharper, even more shrill profile. It has a higher resolution, but its sound lacks the finesse to respect the nuances, in a more polite way, without losing an ounce of the extracted information.

The 5K, stays in the middle, although closer to the profile of the DA3, but clearly improving the resolution level, the cleanliness of the sound and the delicacy of the reproduction. The DA3, however, can be unsettling because of its more punchy sound; with the 5K, you don't get the same feeling. The sound is analytical, but delicate, executed with calm, light, definition and a lot of sharpness. In this way, the notes are appreciated more separated, with more air. The result is bigger, as well as pleasant and not at all tiring. The scene looks bigger than its competitors, with a higher level of three-dimensionality, easily one step above the other two. It can be seen that, the sound is more mature and refined, with more dynamics and transparency, which gives it a more absolute neutrality, allowing a more prolonged use, without neglecting the pleasure that causes its analytical capacity, totally peaceful and calm.



Fiio BTR5

I do not have this model, but being its maximum potential rival, I think it is interesting to attach its differences, shown in the following image with the comparative table:



Conclusion

I haven't been this excited about an audio device in a long time. This lightweight device has stolen my audiophile heart, from the very first note. I would say more, since the first Bluetooth wave. I must confess that I am a sceptic of Bluetooth: I think there could be better data transmission alternatives, with higher bandwidth, better bit rate and speed. Bluetooth has been extended and stretched, to meet some needs, based on a specification that, initially, was not intended for such use, at least with great quality. But then, comes that codec, called LDAC and the implementation of Qudelix, based on the Qualcomm QCC512X platform. And here, is where things change. With the 5K, I was able to combine USB and Bluetooth sources immediately. In this way, it's very easy to look for the 7 differences... or rather, not find any. This has been the myth that has demolished the 5K: the shortcomings of Bluetooth are not in the specification, but in the codec and the subsequent amplification. And that is where Qudelix has embroidered it: it does not matter where the music comes from because its quality is practically the same. And I'm not talking about average quality, but in absolute terms, even higher than its selling price.

The Qudelix-5K is a complete and highly versatile device: it is USB, DAC, amplifier, Bluetooth receiver and has a microphone for making calls. In addition, it is ultra simple to use and has a high level of APP, which allows you to control every detail of all the functions it has. It has a 10-band PEQ/GEQ equalizer, long battery life, 3.5mm and 2.5mm outputs and plenty of power, plus a host of configuration options. A technological achievement and, most importantly, a great sound. Needless to say, nothing more is needed.



Earphones and Sources Used During Analysis

• HiBy R3 Pro
• Xiaomi Redmi Note 8 Pro
• Tempotec Variations V1-A
• SWD2LE
• Smabat ST-10
• Ikko OH10
• NF AUDIO NM2
• BGVP ArtMagic VG4
• ISN H40
• NS Audio NS5 MKII Extra Bass
• Moondrop SSR
• TFZ Live 1
• Takstar Pro 80

Ratings

• Construction and Design: 80
• Accessories: 55
• Connectivity: 93
• Sound: 93
• Quality/Price: 95

Purchase Links

Main Store:
https://www.qudelix.com/collections/frontpage/products/qudelix-5k-dac-amp

Amazon US:
https://www.amazon.com/dp/B088F7C976

AudioHeaven Poland:
https://allegro.pl/oferta/qudelix-5k-dac-amp-2x-es9218p-ldac-aptx-adaptive-9418697083

Munkonggadget Thailand:
https://www.munkonggadget.com/product/dac-amp-Qudelix11365001_5415.html

THZC Trading Limited Hongkong:
https://item.taobao.com/item.htm?ft=t&id=624617682597

XChesser Audio Russia:
https://xchesser.ru/catalog/product/qudelix-5k


You can read the full review in Spanish here