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Qudelix-5K Bluetooth DAC & Headphone Amp

amirm

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#1
This is a review and detailed measurements of the Qudelix-5K USB DAC and balanced headphone amplifier with Bluetooth receiver. I purchased this myself but a member kindly donated one third of the cost. The Qudelix 5K costs US $110 on Amazon including shipping.

The Qudelix comes in a nice looking package with a belt clip:

Qudelix 5K Portable DAC and Headphone Amp Bluetooth LDAC Review.jpg


Note that it has a rechargeable battery built-in so does a lot more than a standard headphone dongle. To wit, you can use it that way to listen using Bluetooth with wide range of codecs supported including LDAC (which I tested below).

"Balanced" output is provided for more power in addition to standard output via 3.5 mm jack:

Qudelix 5K Portable DAC and Headphone Amp Bluetooth LDAC Balanced Jack Review.jpg


On the side are easy to press buttons for volume control, Bluetooth and "VCR" controls (play, stop, etc.). Note that you have dual volume controls: the ones in the host and on the device. The latter have 0.5 dB increments which is very nice. The host volume control is way too coarse for me to dial in the loudness I like.

Bluetooth settings on my Android Samsung S8+ allowed me to turn on LDAC.

There is an App that controls it using Bluetooth. There, you can override the default 1 volt output to 2 volts. And set one of a number of DAC filters as we have in desktop products. There are various profiles you can load in there which I did not play with. It is a super geeky app for enthusiasts.

Qudelix 5K Measurements
Let's treat the unit as a DAC into a high impedance load and see what it does:

Qudelix 5K Portable DAC and Headphone Amp USB Audio Measurements.png


As you see, I had to set the sample rate to 96 kHz as that is the only thing it supports out of the box. I later learned that you can set this in the App but was too lazy to go back and remeasure the dashboard.

Sweeping the output we see that optimal output is much lower than 2 volts:

Qudelix 5K Portable DAC and Headphone Amp USB THD+N vs level Audio Measurements.png


So as a desktop DAC, it would not be a good choice although it would work.

Signal to noise ratio was excellent for a portable device at full output:

Qudelix 5K Portable DAC and Headphone Amp USB Dynamic Range Audio Measurements.png


The 50 mv was in "high" output mode which is supposed to be a bit noisier. As is, it is not bad:

lowest noise headphone adapter dongle review.png


IMD distortion vs level shows what we already know:

Qudelix 5K Portable DAC and Headphone Amp USB IMD Audio Measurements.png


Note how much better it is than the Razer dongle.

Jitter test should be run at 48 kHz but I ran it at 96 khz which may have created some artifacts:

Qudelix 5K Portable DAC and Headphone Amp USB jitter Audio Measurements.png


I was surprised how well the Qudelix did in linearity:

Qudelix 5K Portable DAC and Headphone Amp USB linearity Audio Measurements.png


The above is all appetizer: the main meal for a portable headphone amp is availability of power. Run out of juice and you either can't get enough loudness or heavy distortion sets in which is readily audible. So let's start with 300 ohm load using 3.5mm/unbalanced output:

Qudelix 5K Portable DAC and Headphone Amp USB  Power into 300 ohm unbalanced Audio Measurements.png


Note desktop class noise performance and how it never clips. Max power is a very respectable 23 milliwatts:

Most powerful portable headphone ampllifier 300 ohm review.png


Here is the same using the other extreme with 33 ohm load:

Qudelix 5K Portable DAC and Headphone Amp USB  Power into 33 ohm unbalanced Audio Measurements.png


Most powerful portable headphone ampllifier 33 ohm review.png


Qudelix 5K Balanced Measurements
I happen to have a 50 ohm load in both unbalanced and balanced configuration so here is that comparison:

Qudelix 5K Portable DAC and Headphone Amp USB  Power into 50 ohm balanced Audio Measurements.png


We nicely get 4X the power to the tune of 210 milliwatts which is excellent.

Qudelix 5K Bluetooth Measurements
Let's start with the most common Bluetooth codec, Apt-x:

Qudelix 5K Portable DAC and Headphone Amp USB Bluetooth Apt-x Audio Measurements.png


This is one crappy codec seeing how it can't handle such a simple signal (sinewave) without substantially raising the noise floor. And creating that step in frequencies above 8 kHz or so.

Let's switch to LDAC:

Qudelix 5K Portable DAC and Headphone Amp USB Bluetooth Audio Measurements.png


Now we are talking! Full transparency with same performance as wired USB connection. Note again though that is is a simple sine wave so complex music may not do as well but still, the performance advantage of LDAC is clear (this is was a very short distance test).

Qudelix 5K Listening Tests
I always start with the must brutal test which is my 25 ohm, inefficient Ether CX headphones. This thing chews up a bunch of desktop amps but with a balanced 2.5mm connection to Qudelix, the sound was wonderful. Detailed, good bit of bass performance and loud enough for on the go use. There was no hint of distortion that I could detect.

I then went the other extreme as far as impedance with Sennheiser HD-650 using the unbalanced 3.5 mm connection. Once again there was plenty of volume, good dynamics and no distortion.

All in all a very enjoyable experience.

Conclusions
The DAC performance of the Qudelix 5K is not very good and indeed would get a failing score if it were compared to desktop products. But test the unit in its intended domain which is driving headphones and it comes way on top. There is plenty of power here no doubt due to use of internal battery rather than relying on USB. And wattage here speaks and speaks loudly. Noise is quite low indicating very good design.

Support for LDAC Bluetooth enables much more transparent music playback (objectively anyway -- I have yet to listen to it), which is important here.

Build quality and the App with its tweaking ability completed the package.

So overall, I am happy to recommend the Qudelix 5K. Your search is over for a rich functionality and powerful portable headphone adapater.

------------
As always, questions, comments, recommendations, etc. are welcome.

I planted our musk melon seedlings way too late in the garden so the fruit had no chance to get big. Most were only 2 to 4 inches wide so I almost left them in the field. But being the frugal gardener than I am, I decided to pick and bring them inside anyway. I expected them to be unripe and not sweet. Boy, that was not the case at all:
Musk Melon.jpg


No, it was not like the musk melons that you can get in Japan where you think you died and gone to heaven after the first bite. But still, juicy, sweet and nice. This land of ours definitely delivered this year.....

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Cahudson42

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#3
There are various profiles you can load in there which I did not play with. It is a super geeky app for enthusiasts.
I have been using the Qudelix as part of my bedside system the last few months. A cheap LG Rebel $30 TracFone to drive it with a 3-wire OTG USB cable and Amazon music, while simultaneously controlling via App and bt.

Subjectively, I don't perceive a problem with the DAC SINAD. No hiss. No distortion. (No difference compared to Quad DAC LG V20 and Liquid Spark). HP are HFM HE 400i (original style). And yes, Balanced makes a big difference, IMO. With Balanced, plenty of headroom.

Keep in mind, not only do you get fixed 'various profiles' as Amir mentioned, you get a 10-band full PEQ - just like a top end desktop DAC.

You also, like the top end DACs, get to choose ESS reconstruction filter. FWIW, after a bit of screwing around, I settled on Minimum Phase, Fast. (Which I believe is the Matrix default).

http://www.esstech.com/index.php/en...ophile-dacs/pre-tuned-reconstruction-filters/

I'm 'happy as a clam':)

Thanks for the test, Amir!
 
Last edited:
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#4
I was hoping to see different filters too. I don't understand their description and have no idea which one to use.

Also, as a feature, there is a built-in mic or you can plug in a headset and use headset's mic instead.
 
OP
amirm

amirm

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Thread Starter #5
I was hoping to see different filters too. I don't understand their description and have no idea which one to use.
Use one of the sharp ones (I used Linear Fast).
 

pavuol

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#6
Are these measurement for aptX in its "HD" version? Internet seems to not always agree if S8(+) supports it. If yes, does it have to be enabled manually?
 
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#7
Are these measurement for aptX in its "HD" version? Internet seems to not always agree if S8(+) supports it. If yes, does it have to be enabled manually?
Samsung does not support aptX HD on any of their phones. Android only requires vendors to support SBC, and all other codecs are optional. Each manufacturer decides which codecs to include on their phones.
 

pavuol

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#8
Than again there is a question, if LDAC reached its full potential here (not that it is bad), user manual page 17:

SONY LDAC
• Available with Android 8.0 or higher.
• In general, LDAC 606/660kbps or higher provides excellent sound quality comparable to the wired
interface. If you don't get sufficient sound quality, please set a higher LDAC bit rate in the Android
Developer Options menu.
• Some specific Android smartphones may not be able to provide reliable 990kbps streaming. Turning
off the smartphone display, or using 5GHz WiFi might help the LDAC streamed a little better.
• The LDAC 660kbps is the best trade-off for reliable streaming and sound quality. In most cases, you
would get good enough sound quality with LDAC 660kbps.


Turning off display, Android developer mode.. :facepalm:o_O
 
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amirm

amirm

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Thread Starter #10
Any chance for a multi-tone measurement? :D
Multitone requires 192 kHz sampling. Have to see if it supports it.
 
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amirm

amirm

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Thread Starter #11
Than again there is a question, if LDAC reached its full potential here (not that it is bad), user manual page 17:

SONY LDAC
• Available with Android 8.0 or higher.
• In general, LDAC 606/660kbps or higher provides excellent sound quality comparable to the wired
interface. If you don't get sufficient sound quality, please set a higher LDAC bit rate in the Android
Developer Options menu.
• Some specific Android smartphones may not be able to provide reliable 990kbps streaming. Turning
off the smartphone display, or using 5GHz WiFi might help the LDAC streamed a little better.
• The LDAC 660kbps is the best trade-off for reliable streaming and sound quality. In most cases, you
would get good enough sound quality with LDAC 660kbps.


Turning off display, Android developer mode.. :facepalm:o_O
I have enabled developer mode on my phone and remember seeing those options. But did not mess with them.
 
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#12
Than again there is a question, if LDAC reached its full potential here (not that it is bad), user manual page 17:

SONY LDAC
• Available with Android 8.0 or higher.
• In general, LDAC 606/660kbps or higher provides excellent sound quality comparable to the wired
interface. If you don't get sufficient sound quality, please set a higher LDAC bit rate in the Android
Developer Options menu.
• Some specific Android smartphones may not be able to provide reliable 990kbps streaming. Turning
off the smartphone display, or using 5GHz WiFi might help the LDAC streamed a little better.
• The LDAC 660kbps is the best trade-off for reliable streaming and sound quality. In most cases, you
would get good enough sound quality with LDAC 660kbps.


Turning off display, Android developer mode.. :facepalm:o_O
A problem is that changing the setting in Android Developer Options is only active for the current Bluetooth session. The next time you reconnect on Bluetooth, LDAC will be reset to its default setting (Best Effort — Adaptive Bit Rate). The comment about 5 GHz WiFi is because Bluetooth operates at the same frequencies as 2.4 GHz WiFi, which can interfere with Bluetooth signals. However, in many cases you may not have an option to connect to a WiFi network at 5 GHz.
 

ZolaIII

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#13
Than again there is a question, if LDAC reached its full potential here (not that it is bad), user manual page 17:

SONY LDAC
• Available with Android 8.0 or higher.
• In general, LDAC 606/660kbps or higher provides excellent sound quality comparable to the wired
interface. If you don't get sufficient sound quality, please set a higher LDAC bit rate in the Android
Developer Options menu.
• Some specific Android smartphones may not be able to provide reliable 990kbps streaming. Turning
off the smartphone display, or using 5GHz WiFi might help the LDAC streamed a little better.
• The LDAC 660kbps is the best trade-off for reliable streaming and sound quality. In most cases, you
would get good enough sound quality with LDAC 660kbps.


Turning off display, Android developer mode.. :facepalm:o_O
LDAC doesn't reach it's full potential on buggy Samsung phones, you still need Sony or LG phone (higher tier one's) for that but its irrelevant in this case as it already reaches the DAC capabilities. I don't see this as a good ESS design, good one's reach 100+ dB (100~106) SINAD (Unbalanced) with the same DAC.

Would really like to see the measurements for HiBy R3Pro given in consideration how CS4313 based one's mesured so far.
@amirm next time please try to borrow son's LG for testing.
 
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#17
I don't see this as a good ESS design, good one's reach 100+ dB (100~106) SINAD (Unbalanced) with the same DAC.
Comparisons should be with similar products (tiny Bluetooth receivers using the ES9218P), i.e. one of these: Hiby W5, Shanling UP2, FiiO BTR5, Shanling UP4 (based on info here).
 
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tifune

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#18
Comparisons should be with similar products (tiny Bluetooth receivers using the ES9218P), i.e. one of these: Hiby W5
Would very much like to see the W5 as they offer their own codec which supposedly bests LDAC. Have to use UAPP if I recall correctly, though. I would be happy to have one sent to you , @amirm ? But I'm not sure if your testing hardware would work under such obscure conditions...
 
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