Gustard X18 Review (Stereo DAC)

[srkbear]

You can get a better SINAD by setting volume to -2 dB on the machine's panel instead of your instrument. We integrated an analog attenuator which has better performance.

Thanks for that info. Could you please share what input receiver you implemented in this device? Is it the cs8416?

 

[srkbear]

This is a review and detailed measurements of the Gustard X18 Balanced USB DAC with Bluetooth. It was sent to me by their seller, Shenzhenaudio and costs US $749.

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As you see style is very much the same as other Gustard products. I like the high resolution display with larger volume indicator.

Back panel shows the usual connections:

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Gustard X18 Measurements
Let's start with our usual dashboard with balanced output with digital input adjusted by -2 dB to get nominal 4 volt output:
View attachment 172201

That is extremely good performance. The second harmonic dominates distortion profile but it is down -135 dB (25 dB below threshold of hearing). This easily qualifies X18 as state-of-the-art, placing it in top 3 DACs ever measured:
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EDIT: post these measurements, the company advised that the X18 has a high performance post DAC attenuator and as such, performs better using its volume control than attenuating the input signal. So I tested that with volume set to -2:

View attachment 172530

As you see, the attenuation is slightly less than making the same change in the source. I usually allow 0.1 volt variation but this is a bit much as far as fairness to other DACs. Still, going with it, the X18 changes position to #2 best DAC ever tested:
View attachment 172531


Switching to unbalanced RCA output, we still get superb performance:

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Allowing the output to get up to 5.4 volt, we get even better performance due to increased dynamic range:
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Dynamic range is exceptional:
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Intermodulation+noise performance is superb as expected:

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Jitter test over USB is great:
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But there is some inconsequential jitter components if you use Toslink or Coax:

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Linearity is nailed:
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As usual, you have an array of reconstruction filters to choose from:
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Using default L-FAST, we get extremely clean wideband distortion+noise performance:

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Edit: forgot the multitone test initially:

View attachment 172343

Conclusions
I live for happy days like this: another instrument grade, exceptionally well engineered audio product in the form of X18. It is clear a ton of effort has gone into providing full transparency to input signal. Yes, the cost is up there but if you want the best, you now have one more option.

It is my pleasure to recommend the Gustard X18 DAC.

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

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

Amir, I just noticed that this DAC has a toggle to turn off oversampling. Did this have any influence in your measurements, and what do you make of it? If I missed it my apologies…

 

[Roland68]

Thanks for that info. Could you please share what input receiver you implemented in this device? Is it the cs8416?

No, a CS8416 is not used in the X18 because there is no 28-pin chip on the board.
Since the corresponding chip in the X18 has 32 pins, I assume that it is a CS8422 again.

 

[Pesimista]

I would like a little help with the XLR input to the amplifier:
If the Gustard X18 on the XLR output gives 4.3 Vrms per 100 kΩ, and on the integrated amplifier the XLR inputs are 200 mVrms/100 kΩ, should I use -6 dB attenuation or bypass it when using the balanced input?
The maximum input voltage for the signal is 2.80 Vrms for bypass and 5.60 Vrms with an attenuation of -6 dB (if this information helps).
Maybe I misunderstand the attenuation, and I would ask you to clarify when to include it and when not.

 

[sq225917]

The x18 has a volume control, you're over thinking things just turn the volume down.

 

[FOB69]

Hi,

When the unit is "on", if you unplug it from the wall, then replug it, does the unit starts "on" ?

Thank you for this information.

B.

 

[sq225917]

Yes, it'll start up at the same volume level and selected input as when powered off. I use my A18 this way rather than leave it switched on 24/7

 

[Pesimista]

The x18 has a volume control, you're over thinking things just turn the volume down.

I don't need Gustard volume control, I have an integrated amplifier for that.
What is different when I use a balanced input without -6 dB attenuation, and which is not the case with the RCA input, is the power that the integrated amplifier delivers from the 9 o'clock position.
Compared to RCA as well as to XLR with -6 dB, XLR without attenuation is much louder.
This gives me much higher volume on the BAL1 input than on other single ended inputs, so there is a possibility of unwanted noise when changing inputs if I do not adjust the volume control.
In addition, I would like to know if this attenuation at the balanced input is usable without losing sound quality.
The integrated amplifier is a Yamaha A-S3000, in addition to this balanced input, there is another one that I am not using at the moment.
I tried to find useful information about this amplifier function, but I didn't succeed.
I was hoping that someone more expert than me could explain the advantages and disadvantages of using XLR inputs with and without attenuation.
Thanks in advance!

 

[Roland68]

I don't need Gustard volume control, I have an integrated amplifier for that.
What is different when I use a balanced input without -6 dB attenuation, and which is not the case with the RCA input, is the power that the integrated amplifier delivers from the 9 o'clock position.
Compared to RCA as well as to XLR with -6 dB, XLR without attenuation is much louder.
This gives me much higher volume on the BAL1 input than on other single ended inputs, so there is a possibility of unwanted noise when changing inputs if I do not adjust the volume control.
In addition, I would like to know if this attenuation at the balanced input is usable without losing sound quality.
The integrated amplifier is a Yamaha A-S3000, in addition to this balanced input, there is another one that I am not using at the moment.
I tried to find useful information about this amplifier function, but I didn't succeed.
I was hoping that someone more expert than me could explain the advantages and disadvantages of using XLR inputs with and without attenuation.
Thanks in advance!

Only a resistor is inserted in the signal path for attenuation. There are no pros or cons, this is common to adjust line level.

 

[sq225917]

-30db on the dac volume pot won't change the signal quality

 

[FOB69]

Yes, it'll start up at the same volume level and selected input as when powered off. I use my A18 this way rather than leave it switched on 24/7

Ok, so its keeps in memory the input and volume, but to be sure, will it keep in memory the ON / OFF state too ?
If it has been unplugged "on", i don't want to have to push the front button to set it "on" when i replug it (because i have a main switch for all my audio).

B.

 

[Lambda]

-30db on the dac volume pot won't change the signal quality

How do you know?

Allowing the output to get up to 5.4 volt, we get even better performance due to increased dynamic range:

This showes is not confirming you Hypothesis

The maximum input voltage for the signal is 2.80 Vrms for bypass and 5.60 Vrms with an attenuation of -6 dB (if this information helps).

Then why not uses or why not just turn down the volume on the amp?
I don’t think the amp will have a problem with 5.2V at the input if you just turn down the volume.

 

[Roland68]

How do you know?


This showes is not confirming you Hypothesis

Then why not uses or why not just turn down the volume on the amp?
I don’t think the amp will have a problem with 5.2V at the input if you just turn down the volume.

These values are well outside the audible range.
We once did a blind test with the A18 at 60 and 100% volume. The amplifier was adjusted to within 0.01 volt difference. There was no difference to be heard.

If the amp doesn't have a circuit or OPAMP in front of the volume pot, it doesn't matter. But otherwise, the input circuit could clip or, in the worst case, oscillate.

 

[sq225917]

Also the apx uses different levels to comp for input, so those steps don't exist in the real world. If you can hear a difference of 10 dB in snr while dropping level from 5v to less than 1v you have better ears than me, and anyone else

 

[Lambda]

These values are well outside the audible range.

This is a completely different statement compared to

-30db on the dac volume pot won't change the signal quality

At -30dB your in the SINAD range of 90dB most cellphone internal DACs do better or a 10$ dongle.

This is in the range of what can be head. that's not the point either. point is it WILL change the signal Quality. Significantly
Weather or not you hear it is a different sorry.

 

[Roland68]

This is a completely different statement compared to


At -30dB your in the SINAD range of 90dB most cellphone internal DACs do better or a 10$ dongle.

This is in the range of what can be head. that's not the point either. point is it WILL change the signal Quality. Significantly
Weather or not you hear it is a different sorry.

Please be so kind and read again what SINAD says.
The -30 dB only refers to the reduction in volume on the X18, this has nothing to do with SINAD.
In Amir's measurements you will find a diagram of output voltage/SINAD, if it already has a SINAD of over 112 dB at 0.XX volts, how do you want to get to 90 dB?

 

[Lambda]

At -30dB THD+N is Noise Dominated.
Your not turning down the Noise so your signal to noise gets worse.

There are no absolute noises measures in the review and there is no THD+N messurmetn for -30dB
this is why i said "range" and not exactly or something...

 

[sq225917]

If you can't hear the differences it's academic whatever you want to call it.

 

[FOB69]

Does someone has compare the X16 and X18 ?
There is a thread about it but talks of everything but the X16 X18 sound comparison.

 

[FOB69]

https://confluence.merging.com/download/attachments/9338933/digital-vs-analog-volume-control.pdf?version=1&modificationDate=1481638518000&api=v2