Gustard X18 Measurements

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This unit was loaned to me by Aoshida Audio for testing and review

ChitChat:

The Gustard X18 is an ESS9038 based DAC priced to compete with products such as the Topping D90SE, SMSL D1SE, and Denafrips Ares 2.
The X18 is currently the lowest THD+N / highest SINAD of any DAC I’ve tested. And backs it up with excellent performance in just about all other areas too!

It’s a compelling option for the price and offers a thorough featureset too including bluetooth LDAC support, volume control,
A full video review of my subjective thoughts on the X18 is on the way.

Design:

The X18 is using a single ESS9038 for the DAC. which on the mainboard itself actually is using a heatsink, indicating that the DAC is likely running in current mode as opposed to voltage mode.
I’ve been told by another manufacturer that they subjectively preferred the sound of the 9038 when running in current mode but that it created significantly more heat. The X18 does run fairly warm.

Unlike its bigger brother the X26, the X18 is using a single ESS9038, whereas the X26 Pro uses two ESS9038 chips.

Next there is an Altera MAX V CPLD (CPLD is similar to an FPGA but more ideal for situations where timing is important, such as clock management as it is being used for here. You can read about the differences between FPGAs and CPLDs here).
This handles clock management, the PLL, and supposedly the digital filters/oversampling too though most of the filters seem to just be the stock ESS ones so I’m not entirely sure about that.

Speaking of clocks, the X18 is using two high performance accusilicon oscillators which no doubt contribute to the excellent jitter performance shown later on in this post.

The X18 also features built in bluetooth with aptX HD and LDAC support, so you can use this wirelessly with minimal loss in fidelity compared to a direct connection.

And lastly it does also have MQA support, though as you may already know, I’m not exactly a fan of MQA so in my opinion this just means the product is more expensive than it would otherwise be as it has an MQA licensing fee attached.

Before we look at the measurements, one other aspect to address, the ‘NOS’ mode on both the X18 and the X26 pro are not actually NOS. It is not possible to do NOS on a delta sigma DAC.
The ‘NOS’ function on the X18 just bypasses the initial FIR filter stage but the data still then has to go through the secondary IIR filter/modulation stage, and so the resulting impulse response looks like this:

This function is actually quite useful if you use external oversampling, as it ensures that none of the filter or dithering/noise shaping work done by the external oversampling will be ‘overwritten’ by the internal filtering. Though it’s likely that if you fed the DAC 384khz or 768khz data it’d just be passed through anyway.

Measurements:

Test Setup:

– Audio Precision APx555 B-Series Analyzer with 200kOhm input impedance set unless otherwise specified
– USB Source: Intel PC via intona 7055-C isolator
– Measurement setup and device under test are running on an AudioQuest Niagara 5000 power supply
– Audioquest Mackenzie XLR and RCA interconnects
– Intona Reference Impedance Characterized USB Cable
– Exact analyzer/filter configurations for each measurement are detailed in the full reports

Full Measurement Reports:

Reports available here:

Dynamic Range (AES17): 130.77dB (wow!)

SNR: 132.22dB

IMD SMPTE: -102.64dB

Noise Level RMS (20-20khz): 1.308uVrms

Noise Level RMS (20-90khz): 3.116uVrms

DC Offset: 402uV active, 371uV idle

Latency: 0.88ms

1khz 0dBFS Sine, Balanced Out:

Slightly hot output (and just over 5v range which is most likely done to try to eek out the last bit of performance of the analyzer’s own 5v input sensitivity) but still, the best THD+N performance I’ve tested thus far!

1khz 0dBFS Sine, RCA Out:

1khz -3dBFS Sine, Balanced Out:

-90.31dBFS 1khz sine (96khz capture bandwidth):

The exceptional dynamic range means that low level signals like this are reproduced very cleanly!

Filter Ultrasonic Attenuation:

Idle Noise FFT:

THD+N vs Frequency:

IMD:

Linearity:

Crosstalk:

Jitter:

Jitter performance is truly excellent though is worsened with the addition of the U18.
The U18 will provide galvanic isolation which the X18 does not have internally, but given the performance discrepancy it’d be both cheaper and give a better quality result to purchase an Intona 7055-C or other USB galvanic isolator instead.

Multitone:

Wideband: