Gustard X26 Pro Measurements

Test Setup:

– Audio Precision APx555 B-Series Analyzer with 200kOhm input impedance
– Van Damme Star-Quad shielded SPC XLR cables with Amphenol Connectors
– USB Source: AMD PC via ifi iGalvanic 3.0
– Audioquest Carbon USB and SPDIF cables
– All measurements shown in this post are taken with SPDIF input, 44.1khz sample rate and stock ‘vivid’ filter unless otherwise noted (other input/filter measurements available in reports)
– Full reports containing additional data and test configurations are attached
– Exact analyzer/filter configurations for each measurement are detailed in the full reports
– APx Project is included in the reports folder should anyone wish to repeat this set of measurements or use it for another DAC

ChitChat:

This DAC is an interesting one, it’s quite pricey at about $1500, and offers a few extra/unusual features. It’s not quite the same ‘insert ESS chip and Opamp here for 122dB SINAD’ design, with 10Mhz clock input support, a discrete Class A output stage (with analog LPF) , and a fair amount of extra DSP and clock related stuff.

As a result, this costs twice the price of something such as a D1SE. Whether that is worth it is another question. At $1500 it’s knocking on the door of a lot of very well regarded DACs like the Yggdrasil, Spring 3 etc.

If there are any other measurements you’d like to see they’re most likely in the reports. But if not, let me know and I’ll add them to my sequence for future tests.

Full Reports:

Reports available here:

Reports contain the following measurements:

– 1khz Sine View
– 15khz Sine View
– -90.31dBfs Sine View
– Phase Response
– Filter Ultrasonic Attenuation
– 20hz-90khz RMS Noise Level
– Device Output Level (Vrms)
– 20hz-20khz Noise RMS Level
– Idle Noise FFT
– 1khz FFT (0dBfs and -3dBfs)
– 50hz FFT (0dBfs and -3dBfs)
– Effective Number of Bits (0dBfs and -3dBfs)
– THD+N (0dBfs and -3dBfs)
– THD+N / Frequency
– Dynamic Range (AES17)
– SNR
– IMD (SMPTE)
– 50hz/7khz IMD SMPTE FFT
– IMD SMPTE vs Output Level
– Linearity
– Linearity (No Bandpass)
– SINAD/Output Level
– Crosstalk / Frequency
– DC Offset when Active
– DC Offset when Idle
– 44.1khz Jitter
– 48khz Jitter
– 90khz Bandwidth test
– 32 Tone FFT
– 1.2Mhz Bandwidth Noise FFT
– 1.2Mhz Bandwidth 1khz FFT (0dBfs and -3dBfs)
– And more!

Measurements:

Dynamic Range (AES17): 125.4dB

SNR: 127dB

Noise Level RMS (20-20khz): 2.264uVrms

Noise Level RMS (20-90khz): 4.405uVrms

DC Offset: 567uV Active, 461uV idle

1khz 0dBFS:

Pretty crazy THD+N performance, BUT:

1khz -3dBFS:

Actual SINAD figure is still very good, but it is rather odd that once we stop playing a full scale signal the 3rd harmonic in particular is suddenly almost 15dB higher…..
Not sure if this is an unintentional quirk or something done specifically to optimise for looking good in test conditions.

THD+N / Frequency:

Linearity:

SINAD/THD+N vs output level:

IMD (SMPTE) vs Output Level:

Crosstalk:

-90.31dBfs 1khz Sine (Recorded with 192khz ADC Sample Rate):

Filter Ultrasonic Attenuation:

Gustard says this is a custom/proprietary filter, but it seems to be identical to ESS Fast Linear filter.
D1SE ‘Fast Linear’ vs Gustard ‘Vivid’ filter shown below, can you tell which is which?

Impulse Response:

Gustard also says it ‘supports NOS’. Which is confusing because…well..you can’t really run a delta sigma dac in ‘NOS’.
Looks like the ‘NOS’ option is basically a VERY short minphase filter:

Was sort of expecting a Zero-Order-Hold filter on this one similar to RME’s ‘NOS/Super-Slow’ filter on the ADI-2 which does actually produce a result similar to what you’d expect from a NOS dac.

Idle Noise Spectrum upto 1.2Mhz:

Analog Low Pass FIlter:

Gustard mentioned the analog low-pass filter so I checked that, 192khz input:

44.1khz Jitter (USB):

48khz Jitter (USB):

Multitone:

No matter what I did, I struggled to get a result on this test where the <200hz region wasn’t overly high. This is one of the best results, many of them had noise upto about -100dB.
I’m not entirely sure if this is a measurement configuration issue or the DAC. I’ve encountered it with other DACs sometimes, but in those cases just running the test again or enabling frequency shift correction sorts it.

With the X26 Pro, I really struggled to get this test to work properly so take this with a grain of salt as this is very much a cherrypicked screenshot: