Hello Everyone,
This is a complementary review of the Loxjie D40 Pro.
Preamble
The Loxjie D40 Pro has already been reviewed here by Amir, but as opposed to the SMSL DO400, it is not the same item I'm reviewing, as I bought this one directly from the webstore (on sale at 280$).
I thought it would be a great opportunity to review a different item to check if the performances are consistent.
Loxjie D40 Pro - Presentation
This DAC is an economic version of the SMSL DO400. The functionalities are the same, to the exception of the "sound colors" option absent in the D40 Pro. The display is basic and the remote control is not specific for this DAC, making it a little cumbersome to use without looking at the user manual. Some of the options (like the selection of filters) are directly accessible from the small buttons on the front.
I got the Loxjie D40 Pro at roughly 40% less than the DO400, but do we get almost half the performances? We'll check that.
On the back, nothing is missing:
We get the same set of inputs/outputs, which is cool.
I did not take a picture of the inside of the DO400, I'll do that when I return home next week, but at least this is the Loxjie:
The main differences between the DO400 and the D40 Pro have been shared by @Roland68 on the main SMSL DO400 review post.
User Experience
I like the fact the remote control is not mandatory, and the direct access to some functions (output, filter) from the front buttons. If the interface is very basic, it is still intuitive after one read on the user manual.
As opposed to the SMSL, the Loxjie offers only a preamp mode, so the output voltage can always be adjusted. This is good news since it does not reduce the performances and allow for a better resistance to intersample overs, as I'll show in the review (same as with the SMSL).
When the display shows -0 as volume, it means 4Vrms at balanced outputs (2Vrms unbalanced) and it goes up to +2.0, for 5Vrms output (2.5Vrms unbalanced). Oddly +0.5 means indeed 0.5dB more than the -0 setting, but -1 equals -0.5dB at the output. Go figure.
Loxjie D40 Pro - Measurements
All measurements performed with an E1DA Cosmos ADCiso (grade 0) in mono mode, the Cosmos Scaler (100kohms from unbalanced input) and APU (when required) for analog outputs. I used a Windows 11 PC to connect via USB and did not have to install a driver. I also alternatively used the SMSL PO100 Pro to feed it with Coax and Toslink SPDIF for some complementary tests.
From XLR out (non inverting) I measured:
I aligned this review with the one I made of the SMSL DO400, so not all measurements are aligned with those of Amir, as I explained in that review of the SMSL.
Here we start with the standard 1kHz @0dBFS test tone, and output volume set to 4Vrms (48kHz SR, FFT 32k, 4 averages):
The two channels perform exactly the same with a 126.6dB SINAD. When extending the span to the one of Amir (10Hz to 22.4kHz), the SINAD is 126.3dB.
If the Loxjie is nearly half the price of the SMSL DO400, the loss on SINAD perspective is a small 1dB. And note that from the Coax input, I got 0.3dB better SINAD, meaning you don't lose anything when using it:
Increasing the output volume to 5Vrms got me to 127.5dB average SINAD between the two channels (20Hz to 20kHz) and again 0.3dB lower with Amir's span (10Hz - 22.4kHz).
These are crazy numbers, even if behind the SMSL DO400.
From RCA outputs, I got an average SINAD 122.5dB at 2.5Vrms and almost 2dB less at 2Vrms, which is 2dB less than the SMSL DO400.
----
From experience reviewing CD Players, I like to run the same 1khz test 6dB lower:
The two channels are again identical and very close to what I measured from the SMSL DO400, only a very small 0.4dB weaker.
----
Stereophile was often showing the below and I like it too, so I'm used to reuse it. It is a view from 20Hz to 1kHz with a 1kHz sine at 0dBFS:
This graph allows a better viewing at the power supply potential related noise (leakage) and here there's nothing. I had to do 0 effort to get there, meaning the Loxjie is well isolated on power supply perspective. That said, there is some correlated (pseudo-random) noise at the foot of the fundamental that we see here. It's not a concern, but more than what I measured with the SMSL DO400, meaning some cost cuts show this way, which is reasonable.
----
Since I'm here, let me add the 50Hz @0dBFS into 600ohms, for compatibility with Stereophile measurements:
Besides the higher than usual noise floor at the foot of the fundamental, this trace is very clean, with only the H3 showing itself and then no subsequent harmonics of the 50Hz.
----
There is a selection of oversampling filters, and some are really flat in audio band, but not all of them. The below is a wideband analysis of white noise @-10dBFS, volume set at 0dB, with 44.1kHz input sampling rate:
They are identical to those of the SMSL DO400, and they are the ones of the ESS9039. I recommend Filter 3 which is the Linear Phase Fast Roll-off of the ESS DAC.
The only exception is Filter0, meaning "Filter OFF" as per the documentation of Loxjie. And exactly same as with the SMSL DO400, it plays 6dB higher and clips the output stage at -3.5dB relative to 4Vrms output. Look:
With volume set at -7 (equivalent to -3.5dB), I measured an output level of 5.714Vrms. With volume set at +2 (i.e 5.5dB more), I got 6.839Vrms, so the output stage is clipped (it should be going to 10Vrms).
This filter is useless and potentially dangerous for the other elements down the line, especially your loudspeakers. Just avoid it, or at least keep the volume at -8.
----
Let's go back to good news with the Jitter Test (48kHz, 512k FFT. 32 averages):
This is SOTA trace. The low frequency "stressor" component of the jitter test can be (very) well seen at low frequency, meaning very low noise floor. We get again that small correlated noise at the foot of the fundamental but no visible side bands while the FFT analysis goes down to -165dBr!
----
Of course, I won't forget the Multitone test (48kHz SR, 256k FFT, 16 averages):
It is revealing the increased noise floor (with signal close to full scale) that I already mentioned several times, and that manifests itself up to 200Hz. This is the real impact of the cost cut of the Loxjie when compared to the SMSL DO400. That said, being at low frequencies, where our ears are much less sensitive, I don't think it is a big issue.
----
Next is the THD+N vs Frequency (192kHz, 512k FFT 4 averages, 3PPO (20Hz to 20kHz), 4Vrms output):
This test is hitting the max resolution of the ADC, but less so than the SMSL. Basically the Loxjie has up to 6dB more distortion and noise than the SMSL DO400. Below 100Hz, the limitation comes from the correlated noise and the foot of the fundamental (again).
All that said, you see from the plot at 1kHz, we get almost -113dB THD+N at 1kHz, with all noise included up to 90kHz (Filter 3). This is still a very good performance! The other channel overlays perfectly.
----
Next is the IMD SMPTE vs output level sweep, which can't be compared to the one of Amir because this measurement is based on FFT analysis of IMD distortion only (192kHz, 128k FFT 4 averages, 1dB step, scaler in auto mode):
This trace is very close to the one of the SMSL DO400. The issue I reported before does not show here due to the nature of the test (IMD distortion components are calculated around the 7kHz test tone).
----
Dynamic range is extremely good, be it CCIR-2K weighted or A-Weighted (0dBFS = 4Vrms):
Again we lose only 2dB of performance when compared with the SMSL DO400, no audible consequences, of course, these are crazy good numbers.
----
And now let's have a look at other less usual measurements. The one that I like is the resistance to intersample-overs.
This test is performed with dedicated test tones with a specific phase shift to generate digital overs. If anything in the digital path (oversampling filter / DSP / ASRC) does not have enough headroom for digital overs, it will generate clipping within the interpolator.
For that, I'm using a test tone of 11'025Hz with a phase shift of 45° that goes up to +3.01dB over, by 1dB steps. This allows me to process what's the headroom of the digital interpolator of the DAC. Here are the results (THD+N measurement up to 90kHz):
The above means that at full output power (5Vrms from XLR), the interpolator of the Loxjie (Linear Fast filter) has a headroom of only 1dB. But because the volume control is done in digital domain, before interpolation, there is more than 3dB headroom when lowering the volume by... 3dB.
So, with volume set at -02 (=-1dB), you get the best ISO resistance. I recommend reducing the volume that way, even if you use the Loxjie as a DAC (without needing volume control), since so many master are too hot. The penalty on SINAD is negligible, especially considering how good it is at 4Vrms.
Note that the best result (-102dB) is driven by distortion, not noise, and the SMSL DO400 was reaching -115dB of THD+N. That will not change anything to your ears, since we are talking first harmonic at 22kHz.
----
Other measurements (not shown):
----
Last and not least, I wanted to take the opportunity to revisit the linearity test, since these latest DACs are so good. Here we go:
Instead of the standard view starting at -120dBFS, I decided to start it at -140dBFS (end at -80dBFS). If we define the threshold of linearity as 0.2dB deviation from the desired output voltage, then the Loxjie easily reaches the staggering result of -131dBFS (same for the two channels).
And that is with the 0dBFS defined as 4Vrms. Relative to 5Vrms, linearity is 2dB better! Let's start chasing -140dBFS
Loxjie D40 Pro - Measurements - Headphones
In high gain mode, I got an already very high 9Vrms with volume set at -14 (=-7dB) into 200kΩ, meaning a max 25Vrms.
In low gain mode, at -0 volume, I got a high 3.926vRMSVrms output (into 200kΩ) from the 4.4mm jack. These are the same as the SMSL D0400.
In low gain mode, 4Vrms output, the 1kHz @0dBFS is the below:
This is very close to the SMSL DO400 which achieved -121.5dB of THD+N on the same test.
At 50mVrms output, in low gain mode, I get a little disappointing SNR of 84.1dB:
This is only 0.5dB less than the SMSL DO400, and concurs with the findings of Amir.
Conclusion
For almost half the price of the SMSL DO400, we certainly have more than half the performances.
The issues I spotted were not revealed by the testing of Amir's device, which is probably an indication of potential variations related to some cost cuts between two devices.
Basically, if the device that Amir reviewed is the best and mine represents the worst, then you still get a super high resolved DAC in all cases.
I hope you enjoyed this review!
Flo
This is a complementary review of the Loxjie D40 Pro.
Preamble
The Loxjie D40 Pro has already been reviewed here by Amir, but as opposed to the SMSL DO400, it is not the same item I'm reviewing, as I bought this one directly from the webstore (on sale at 280$).
I thought it would be a great opportunity to review a different item to check if the performances are consistent.
Loxjie D40 Pro - Presentation
This DAC is an economic version of the SMSL DO400. The functionalities are the same, to the exception of the "sound colors" option absent in the D40 Pro. The display is basic and the remote control is not specific for this DAC, making it a little cumbersome to use without looking at the user manual. Some of the options (like the selection of filters) are directly accessible from the small buttons on the front.
I got the Loxjie D40 Pro at roughly 40% less than the DO400, but do we get almost half the performances? We'll check that.
On the back, nothing is missing:
We get the same set of inputs/outputs, which is cool.
I did not take a picture of the inside of the DO400, I'll do that when I return home next week, but at least this is the Loxjie:
The main differences between the DO400 and the D40 Pro have been shared by @Roland68 on the main SMSL DO400 review post.
User Experience
I like the fact the remote control is not mandatory, and the direct access to some functions (output, filter) from the front buttons. If the interface is very basic, it is still intuitive after one read on the user manual.
As opposed to the SMSL, the Loxjie offers only a preamp mode, so the output voltage can always be adjusted. This is good news since it does not reduce the performances and allow for a better resistance to intersample overs, as I'll show in the review (same as with the SMSL).
When the display shows -0 as volume, it means 4Vrms at balanced outputs (2Vrms unbalanced) and it goes up to +2.0, for 5Vrms output (2.5Vrms unbalanced). Oddly +0.5 means indeed 0.5dB more than the -0 setting, but -1 equals -0.5dB at the output. Go figure.
Loxjie D40 Pro - Measurements
All measurements performed with an E1DA Cosmos ADCiso (grade 0) in mono mode, the Cosmos Scaler (100kohms from unbalanced input) and APU (when required) for analog outputs. I used a Windows 11 PC to connect via USB and did not have to install a driver. I also alternatively used the SMSL PO100 Pro to feed it with Coax and Toslink SPDIF for some complementary tests.
From XLR out (non inverting) I measured:
- At -0 setting: 4.080Vrms from right channel and 4.087Vrms from Left one, i.e. 0.01dB channel imbalance.
- At +2.0 setting: 5.134Vrms from right channel and 5.144Vrms from Left one, i.e. 0.01dB channel imbalance.
- At -0 setting: 1.979Vrms from right channel and 1.982Vrms from Left one, i.e. 0.02dB channel imbalance.
- At +2.0 setting: 2.491Vrms from right channel and 2.495Vrms from Left one, i.e. 0.02dB channel imbalance.
I aligned this review with the one I made of the SMSL DO400, so not all measurements are aligned with those of Amir, as I explained in that review of the SMSL.
Here we start with the standard 1kHz @0dBFS test tone, and output volume set to 4Vrms (48kHz SR, FFT 32k, 4 averages):
The two channels perform exactly the same with a 126.6dB SINAD. When extending the span to the one of Amir (10Hz to 22.4kHz), the SINAD is 126.3dB.
If the Loxjie is nearly half the price of the SMSL DO400, the loss on SINAD perspective is a small 1dB. And note that from the Coax input, I got 0.3dB better SINAD, meaning you don't lose anything when using it:
Increasing the output volume to 5Vrms got me to 127.5dB average SINAD between the two channels (20Hz to 20kHz) and again 0.3dB lower with Amir's span (10Hz - 22.4kHz).
These are crazy numbers, even if behind the SMSL DO400.
From RCA outputs, I got an average SINAD 122.5dB at 2.5Vrms and almost 2dB less at 2Vrms, which is 2dB less than the SMSL DO400.
----
From experience reviewing CD Players, I like to run the same 1khz test 6dB lower:
The two channels are again identical and very close to what I measured from the SMSL DO400, only a very small 0.4dB weaker.
----
Stereophile was often showing the below and I like it too, so I'm used to reuse it. It is a view from 20Hz to 1kHz with a 1kHz sine at 0dBFS:
This graph allows a better viewing at the power supply potential related noise (leakage) and here there's nothing. I had to do 0 effort to get there, meaning the Loxjie is well isolated on power supply perspective. That said, there is some correlated (pseudo-random) noise at the foot of the fundamental that we see here. It's not a concern, but more than what I measured with the SMSL DO400, meaning some cost cuts show this way, which is reasonable.
----
Since I'm here, let me add the 50Hz @0dBFS into 600ohms, for compatibility with Stereophile measurements:
Besides the higher than usual noise floor at the foot of the fundamental, this trace is very clean, with only the H3 showing itself and then no subsequent harmonics of the 50Hz.
----
There is a selection of oversampling filters, and some are really flat in audio band, but not all of them. The below is a wideband analysis of white noise @-10dBFS, volume set at 0dB, with 44.1kHz input sampling rate:
They are identical to those of the SMSL DO400, and they are the ones of the ESS9039. I recommend Filter 3 which is the Linear Phase Fast Roll-off of the ESS DAC.
The only exception is Filter0, meaning "Filter OFF" as per the documentation of Loxjie. And exactly same as with the SMSL DO400, it plays 6dB higher and clips the output stage at -3.5dB relative to 4Vrms output. Look:
With volume set at -7 (equivalent to -3.5dB), I measured an output level of 5.714Vrms. With volume set at +2 (i.e 5.5dB more), I got 6.839Vrms, so the output stage is clipped (it should be going to 10Vrms).
This filter is useless and potentially dangerous for the other elements down the line, especially your loudspeakers. Just avoid it, or at least keep the volume at -8.
----
Let's go back to good news with the Jitter Test (48kHz, 512k FFT. 32 averages):
This is SOTA trace. The low frequency "stressor" component of the jitter test can be (very) well seen at low frequency, meaning very low noise floor. We get again that small correlated noise at the foot of the fundamental but no visible side bands while the FFT analysis goes down to -165dBr!
----
Of course, I won't forget the Multitone test (48kHz SR, 256k FFT, 16 averages):
It is revealing the increased noise floor (with signal close to full scale) that I already mentioned several times, and that manifests itself up to 200Hz. This is the real impact of the cost cut of the Loxjie when compared to the SMSL DO400. That said, being at low frequencies, where our ears are much less sensitive, I don't think it is a big issue.
----
Next is the THD+N vs Frequency (192kHz, 512k FFT 4 averages, 3PPO (20Hz to 20kHz), 4Vrms output):
This test is hitting the max resolution of the ADC, but less so than the SMSL. Basically the Loxjie has up to 6dB more distortion and noise than the SMSL DO400. Below 100Hz, the limitation comes from the correlated noise and the foot of the fundamental (again).
All that said, you see from the plot at 1kHz, we get almost -113dB THD+N at 1kHz, with all noise included up to 90kHz (Filter 3). This is still a very good performance! The other channel overlays perfectly.
----
Next is the IMD SMPTE vs output level sweep, which can't be compared to the one of Amir because this measurement is based on FFT analysis of IMD distortion only (192kHz, 128k FFT 4 averages, 1dB step, scaler in auto mode):
This trace is very close to the one of the SMSL DO400. The issue I reported before does not show here due to the nature of the test (IMD distortion components are calculated around the 7kHz test tone).
----
Dynamic range is extremely good, be it CCIR-2K weighted or A-Weighted (0dBFS = 4Vrms):
Again we lose only 2dB of performance when compared with the SMSL DO400, no audible consequences, of course, these are crazy good numbers.
----
And now let's have a look at other less usual measurements. The one that I like is the resistance to intersample-overs.
This test is performed with dedicated test tones with a specific phase shift to generate digital overs. If anything in the digital path (oversampling filter / DSP / ASRC) does not have enough headroom for digital overs, it will generate clipping within the interpolator.
For that, I'm using a test tone of 11'025Hz with a phase shift of 45° that goes up to +3.01dB over, by 1dB steps. This allows me to process what's the headroom of the digital interpolator of the DAC. Here are the results (THD+N measurement up to 90kHz):
| Intersample-overs tests THD+N 20Hz - 90kHz | Peak = -0.99dBFS | Peak = +0.01dBFS | Peak = +1.01dBFS | Peak = +2.01dBFS | Peak = +3.01dBFS |
| Loxjie D40 Pro (Vol +2dB) | -102dB | -102dB | -40.9dB | -25.2dB | -20.4dB |
| Loxjie D40 Pro (Vol 0dB) | -102dB | -102dB | -102dB | -102dB | -40.8dB |
| Loxjie D40 Pro (vol -1dB) | -102dB | -102dB | -102dB | -102dB | -102dB |
The above means that at full output power (5Vrms from XLR), the interpolator of the Loxjie (Linear Fast filter) has a headroom of only 1dB. But because the volume control is done in digital domain, before interpolation, there is more than 3dB headroom when lowering the volume by... 3dB.
So, with volume set at -02 (=-1dB), you get the best ISO resistance. I recommend reducing the volume that way, even if you use the Loxjie as a DAC (without needing volume control), since so many master are too hot. The penalty on SINAD is negligible, especially considering how good it is at 4Vrms.
Note that the best result (-102dB) is driven by distortion, not noise, and the SMSL DO400 was reaching -115dB of THD+N. That will not change anything to your ears, since we are talking first harmonic at 22kHz.
----
Other measurements (not shown):
- First, I now regroup all IMD tests as below, sourced from REW's results (IMD distortion and Total Distortion+Noise shown for each):
- Crosstalk: -140dB (1kHz)
- Pitch Error (GPSDO corrected) : 19'996.95Hz (19'997Hz requested) ie -2.5ppm
----
Last and not least, I wanted to take the opportunity to revisit the linearity test, since these latest DACs are so good. Here we go:
Instead of the standard view starting at -120dBFS, I decided to start it at -140dBFS (end at -80dBFS). If we define the threshold of linearity as 0.2dB deviation from the desired output voltage, then the Loxjie easily reaches the staggering result of -131dBFS (same for the two channels).
And that is with the 0dBFS defined as 4Vrms. Relative to 5Vrms, linearity is 2dB better! Let's start chasing -140dBFS
Loxjie D40 Pro - Measurements - Headphones
In high gain mode, I got an already very high 9Vrms with volume set at -14 (=-7dB) into 200kΩ, meaning a max 25Vrms.
In low gain mode, at -0 volume, I got a high 3.926vRMSVrms output (into 200kΩ) from the 4.4mm jack. These are the same as the SMSL D0400.
In low gain mode, 4Vrms output, the 1kHz @0dBFS is the below:
This is very close to the SMSL DO400 which achieved -121.5dB of THD+N on the same test.
At 50mVrms output, in low gain mode, I get a little disappointing SNR of 84.1dB:
This is only 0.5dB less than the SMSL DO400, and concurs with the findings of Amir.
Conclusion
For almost half the price of the SMSL DO400, we certainly have more than half the performances.
The issues I spotted were not revealed by the testing of Amir's device, which is probably an indication of potential variations related to some cost cuts between two devices.
Basically, if the device that Amir reviewed is the best and mine represents the worst, then you still get a super high resolved DAC in all cases.
I hope you enjoyed this review!
Flo
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