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Loxjie D30 DAC and Headphone Amplifier Review

amirm

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#1
This is a review and detailed measurements of the Loxjie D30 DAC with Bluetooth and headphone amplifier. It was kindly sent to me by the company. It costs US $160 from the one site I can find that is selling it currently.

The D30 is a departure from previous Loxjie products with odd shapes and such:

Loxjie D30 USB DAC and Headphone Amplifier DSD stereo review.jpg


The high resolution display is informative and quite nice. A cool feature is that it remembers the headphone volume level and pre-out independently. So there is no risk of blowing up one or the other with inappropriate level set for the other device.

I love that it has an included mains power supply so you don't have to deal with an external supply:

Loxjie D30 USB DAC and Headphone Amplifier Bluetooth back panel stereo review.jpg


Clearly good attempt has been made to get the functionality right first before worrying about looks.

DAC Audio Measurements
The output was a bit higher than 2 volt that we aim for in our testing so I dialed it down a bit to get to 2 volts:

Loxjie D30 USB DAC and Headphone Amplifier DSD Audio Measurements.png


This reduced the SINAD by 1 dB which is inline with what Loxjie has published. At 114 dB, this firmly places the D30 in excellent category of all DACs tested:

best dac and headphone amplifier review with bluetooth.png


Dynamic range falls in the same category:

Loxjie D30 USB DAC and Headphone Amplifier DSD Dynamic Range Audio Measurements.png


Intermodulation distortion is excellent:

Loxjie D30 USB DAC and Headphone Amplifier DSD IMD Audio Measurements.png


32-tone signal resembling "music" shows very low distortion levels, albeit with a bit of uptick in midfrequencies:

Loxjie D30 USB DAC and Headphone Amplifier DSD Multitone Audio Measurements.png


Jitter on both USB and Toslink was more than what I like:

Loxjie D30 USB DAC and Headphone Amplifier DSD Jitter Audio Measurements.png


THD+N versus frequency was fine in one channel but worse in the other:
Loxjie D30 USB DAC and Headphone Amplifier DSD THD+N vs Frequency Audio Measurements.png


Precision as reflected in our linearity test is excellent:

Loxjie D30 USB DAC and Headphone Amplifier DSD Linearity Audio Measurements.png


Usual set of filters are provided:

Loxjie D30 USB DAC and Headphone Amplifier DSD Filter Audio Measurements.png


Headphone Amplifier Measurements
Let's start with power output using 300 ohm:

Loxjie D30 USB DAC and Headphone Amplifier DSD Headphone Power 300 ohm Audio Measurements.png


My target here is 100 milliwatt and the D30 misses that by fair bit. So it will get loud but will have limits. Fortunately there is no sign of distortion so you would be good to max volume.

Switching to 33 ohm we get:

Loxjie D30 USB DAC and Headphone Amplifier DSD Headphone Power 33 ohm Audio Measurements.png


Signal to noise ratio for very low output level is not that great:

Loxjie D30 USB DAC and Headphone Amplifier DSD Headphone 50 mv Audio Measurements.png


Lowest noise dac and headphone amplifier review 2020.png


Bluetooth Audio Measurements
There has been requests on and off for Bluetooth performance measurements. Given the lossy nature of the codecs used in BT, what you see reflects that performance and not the DAC itself. As such, the results should be transferrable to many other DACs with Bluetooth inputs (or Bluetooth devices in general). The source here was my Samsung S8+ so there may be some variation depending on how good the encoders are in my phone.

Let's start with the default and most common codec, aptX:

Loxjie D30 USB DAC and Headphone Amplifier DSD Bluetooth Aptx Audio Measurements.png


The spectrum shows the typical signature of this codec with filtering of frequencies above 5 kHz. We have lost some 50 dB in fidelity versus uncompressed as well. Noise has sharply increased.

Here is the original music codec in BT, namely SBC:

Loxjie D30 USB DAC and Headphone Amplifier DSD Bluetooth SBC Audio Measurements.png


The filtering is gone but replaced with a lot of junk. Performance is up 4 dB in total.

Both SBC and aptX are non-perceptual codecs. They don't have a psychoacoustics model to decide what to keep and what not to. They rely on inherent redundancy in the music data to compress it (in case of a single sine wave used here, that should have been most efficient). In contrast, the next choice, the AAC codec, is an excellent perceptually based lossy codec which makes encoding much more "expensive" in the form of CPU cycles but should generate better results:

Loxjie D30 USB DAC and Headphone Amplifier DSD Bluetooth AAC Audio Measurements.png


We do get better performance to the tune of 11 dB better SINAD. But this is still horrible. A single sine wave should be a walk in the park for a perceptual codec. There is no excuse for noise around the shoulders of our main tone. The other spikes are harmonic distortion which may be generated by the analog output of the Bluetooth module used.

I tried LDAC but it did not work so I assume it is not supported in D30. If possible I like to see the DAC display the codec in use for Bluetooth.

Headphone Listening Tests
The D30 had no trouble powering my very low sensitivity, low impedance Drop Ether CX. It got loud enough to be very usable with no hint of distortion. Normal listening would be at 80 to 90% volume. Note however that with music recorded at low level, I had to ride the volume to max. Same situation existed with Sennheiser HD-650 headphones. No distortion, loud enough to almost get uncomfortable and excellent fidelity.

Conclusions
The Loxjie targets the most common configuration and features one needs for a desktop product: DAC, headphone amp and bluetooth. The DAC performance is excellent. Anything better would cost you hundreds of dollars more. The headphone amplifier has very good noise and distortion but limited power. And too high a noise floor for sensitive IEMs. Still, as an included amplifier, it does the job for most people.

I debated if I should give the D30 the golfing panther or "I like it" one. At the end, I remembered all the requests I get for a great all-in-one DAC and headphone amp at a reasonable price and this fits the bill most perfectly. To get better, you need to go to a stack of two boxes at a cost of $200. And analog volume control which may cause channel differential.

I am happy to recommend the Loxjie D30.


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

Spent the entire yesterday canning our latest harvest. Had planted a bunch of beautiful carrots back in spring. Did not eat them fast enough so decided to pickle them. Here is a shot of them ready to go:

Colorful Carrots.jpg


They have stronger color variations before pealing. Many have orange insides despite the skin being different on the outside. I did get a kick out of the green one being that way on the outside and inside. Bye carrots! See you next late spring.

Helper is out there digging the new trench for the septic pipe. It is right at the foundation of the house and above deck. And the heat pump. Hopefully when it is all done the side of the house won't cave in! Your prayers in the form of monetary donations would be much appreciated: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
OP
amirm

amirm

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Thread Starter #2
Oh, just noticed the 48 kHz on the BT display. Some of the Bluetooth artifacts may have been caused by the resampler in Android.
 

MediumRare

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#4
If the worst distortion component on the APTx FFT is better than -90 dB, where did the other -24 dB of SINAD go to? The noise floor doesn't look high so where do we see it?
 

ninetylol

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#5
Thanks for the review Amir. Guess I was lucky buying this thing blind last week :)

Also the amp did better than i was expecting. Bought the L30 for that, so I have peace of mind.

EDIT: @amirm did you measure RCA out impedance by any chance?
 
Last edited:

PuX

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#6
And analog volume control which may cause channel differential.
Is there a reason why volume is usually analogue on headphone amps? Are potentiometers just a cost-effective way to do it? Or digital volume would be an extra chain in an amp that should be avoided?

I can only remember Arcam rHead as an example of an amp with relatively perfect channel balance. And even in that case volume is not digital, as far as I understand (resistor ladder isn't digital, is it?).
 

PeteL

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#7
Is there a reason why volume is usually analogue on headphone amps? Are potentiometers just a cost-effective way to do it? Or digital volume would be an extra chain in an amp that should be avoided?

I can only remember Arcam rHead as an example of an amp with relatively perfect channel balance. And even in that case volume is not digital, as far as I understand (resistor ladder isn't digital, is it?).
An headphone amp by definition is analog. Did you mean in cases like this one where you have both a dac and an amp in the same box? Then the answer is not as definite.
 

q3cpma

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#9
Is there a reason why volume is usually analogue on headphone amps? Are potentiometers just a cost-effective way to do it? Or digital volume would be an extra chain in an amp that should be avoided?

I can only remember Arcam rHead as an example of an amp with relatively perfect channel balance. And even in that case volume is not digital, as far as I understand (resistor ladder isn't digital, is it?).
I do think that analogue volume lets you conserve SNR as the noise is also reduced with the gain. And SNR matters a lot when the driver is a few centimers from your ear.
 

voodooless

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#10
Is there a reason why volume is usually analogue on headphone amps?
There is a slight SNR advantage with an analog volume control, specially at lower volumes

Are potentiometers just a cost-effective way to do it? Or digital volume would be an extra chain in an amp that should be avoided?
The digital volume control is free.. it’s part of the DAC internals and is always there, even when not used. A pot will always add additional cost.
 
OP
amirm

amirm

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Thread Starter #12
If the worst distortion component on the APTx FFT is better than -90 dB, where did the other -24 dB of SINAD go to? The noise floor doesn't look high so where do we see it?
There is about 30 dB of "FFT" gain in those graphs. So a noise floor of -90 in FFT is in reality around -60.
 
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amirm

amirm

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Thread Starter #13
EDIT: @amirm did you measure RCA out impedance by any chance?
I did not. Have to use a completely separate program for that and currently that one doesn't work for digital inputs.
 

daftcombo

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#14
This is a review and detailed measurements of the Loxjie D30 DAC with Bluetooth and headphone amplifier. It was kindly sent to me by the company. It costs US $160 from the one site I can find that is selling it currently.

The D30 is a departure from previous Loxjie products with odd shapes and such:

View attachment 87538

The high resolution display is informative and quite nice. A cool feature is that it remembers the headphone volume level and pre-out independently. So there is no risk of blowing up one or the other with inappropriate level set for the other device.

I love that it has an included mains power supply so you don't have to deal with an external supply:

View attachment 87539

Clearly good attempt has been made to get the functionality right first before worrying about looks.

DAC Audio Measurements
The output was a bit higher than 2 volt that we aim for in our testing so I dialed it down a bit to get to 2 volts:

View attachment 87540

This reduced the SINAD by 1 dB which is inline with what Loxjie has published. At 114 dB, this firmly places the D30 in excellent category of all DACs tested:

View attachment 87541

Dynamic range falls in the same category:

View attachment 87542

Intermodulation distortion is excellent:

View attachment 87543

32-tone signal resembling "music" shows very low distortion levels, albeit with a bit of uptick in midfrequencies:

View attachment 87544

Jitter on both USB and Toslink was more than what I like:

View attachment 87545

THD+N versus frequency was fine in one channel but worse in the other:
View attachment 87546

Precision as reflected in our linearity test is excellent:

View attachment 87547

Usual set of filters are provided:

View attachment 87549

Headphone Amplifier Measurements
Let's start with power output using 300 ohm:

View attachment 87550

My target here is 100 milliwatt and the D30 misses that by fair bit. So it will get loud but will have limits. Fortunately there is no sign of distortion so you would be good to max volume.

Switching to 33 ohm we get:

View attachment 87551

Signal to noise ratio for very low output level is not that great:

View attachment 87553

View attachment 87552

Bluetooth Audio Measurements
There has been requests on and off for Bluetooth performance measurements. Given the lossy nature of the codecs used in BT, what you see reflects that performance and not the DAC itself. As such, the results should be transferrable to many other DACs with Bluetooth inputs (or Bluetooth devices in general). The source here was my Samsung S8+ so there may be some variation depending on how good the encoders are in my phone.

Let's start with the default and most common codec, aptX:

View attachment 87554

The spectrum shows the typical signature of this codec with filtering of frequencies above 5 kHz. We have lost some 50 dB in fidelity versus uncompressed as well. Noise has sharply increased.

Here is the original music codec in BT, namely SBC:

View attachment 87555

The filtering is gone but replaced with a lot of junk. Performance is up 4 dB in total.

Both SBC and aptX are non-perceptual codecs. They don't have a psychoacoustics model to decide what to keep and what not to. They rely on inherent redundancy in the music data to compress it (in case of a single sine wave used here, that should have been most efficient). In contrast, the next choice, the AAC codec, is an excellent perceptually based lossy codec which makes encoding much more "expensive" in the form of CPU cycles but should generate better results:

View attachment 87556

We do get better performance to the tune of 11 dB better SINAD. But this is still horrible. A single sine wave should be a walk in the park for a perceptual codec. There is no excuse for noise around the shoulders of our main tone. The other spikes are harmonic distortion which may be generated by the analog output of the Bluetooth module used.

I tried LDAC but it did not work so I assume it is not supported in D30. If possible I like to see the DAC display the codec in use for Bluetooth.

Headphone Listening Tests
The D30 had no trouble powering my very low sensitivity, low impedance Drop Ether CX. It got loud enough to be very usable with no hint of distortion. Normal listening would be at 80 to 90% volume. Note however that with music recorded at low level, I had to ride the volume to max. Same situation existed with Sennheiser HD-650 headphones. No distortion, loud enough to almost get uncomfortable and excellent fidelity.

Conclusions
The Loxjie targets the most common configuration and features one needs for a desktop product: DAC, headphone amp and bluetooth. The DAC performance is excellent. Anything better would cost you hundreds of dollars more. The headphone amplifier has very good noise and distortion but limited power. And too high a noise floor for sensitive IEMs. Still, as an included amplifier, it does the job for most people.

I debated if I should give the D30 the golfing panther or "I like it" one. At the end, I remembered all the requests I get for a great all-in-one DAC and headphone amp at a reasonable price and this fits the bill most perfectly. To get better, you need to go to a stack of two boxes at a cost of $200. And analog volume control which may cause channel differential.

I am happy to recommend the Loxjie D30.


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

Spent the entire yesterday canning our latest harvest. Had planted a bunch of beautiful carrots back in spring. Did not eat them fast enough so decided to pickle them. Here is a shot of them ready to go:

View attachment 87558

They have stronger color variations before pealing. Many have orange insides despite the skin being different on the outside. I did get a kick out of the green one being that way on the outside and inside. Bye carrots! See you next late spring.

Helper is out there digging the new trench for the septic pipe. It is right at the foundation of the house and above deck. And the heat pump. Hopefully when it is all done the side of the house won't cave in! Your prayers in the form of monetary donations would be much appreciated: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Thanks Amir!
Did you listen with a BT source also?
 
OP
amirm

amirm

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Thread Starter #15
Thanks Amir!
Did you listen with a BT source also?
I did not. Long time ago I planned to write a detailed report and listening tests on Bluetooth but time has not permitted such. I did do a casual comparison with a car stereo once and difference was audible there.
 

Matias

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#16
Great all in one device for the price!
 
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#17
I suppose this doesn't have Bass/treble/Loudness/EQ controls I really crave for right?
(and so I have to save up for RME ADI-2 hehe?)
 

bobbooo

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#18
Oh, just noticed the 48 kHz on the BT display. Some of the Bluetooth artifacts may have been caused by the resampler in Android.
Cool to see the Bluetooth measurements and exactly how they mangle the signal, thanks! It would be great to see LDAC (and aptX-HD) measurements in the future if a device supports them. As for Android resampling to 48 kHz, Neutron Player can bypass that not only for wired but I believe also for Bluetooth connections too (maybe this could be tested). Soomal.com did measure the Samsung Galaxy S10+ (which uses the same audio chip as your S8+) showing an increase in distortion going from not-resampled 48 kHz (0.0017%), to 44.1 kHz upsampled to 48 kHz (0.0021%) with Bluetooth playback (LDAC).

48 kHz (no resampling):



44.1 kHz (upsampled to 48 kHz):

 
Last edited:
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