Test and measurement: Hardware and Sound cards for audio measurement

The E1DA is a recent entry to the market and has received good reviews and has superb specifications.
Specifications:
Device purpose /marketing target:
ultra-low THD+N Analog to PCM Digital Converter for audio measurement,
E1DA 9038S/D DACs users, DIYers, audio tech bloggers-reviewers
Status: production
Materials: Sandblasted/black anodized aluminum/laser mark/ES9822Pro/OPA1612
Susumu, Viking resistors, Murata, Samsung C0G caps, Taiwanese connectors/switches
Dimensions: PCBA 90x50x29mm
104x61x39mm
Weight: PCBA 34g
157g
Power: USB-C +5V rail, less than 250mA current
Input: USB bridge Comtrue CT7601CR custom FW
XLR L/R (FDA) up to 10Vrms
AUX 2.5mm jack up to 43Vrms
Output: USB-C, PCM up to 32b/384kHz
Latency: 5mS@192k ASIO4ALL REW - measured as a physical delay/2 from ADC input to the 9038D output
Input ranges /impedance:
1.7Vrms 640Ω
2.7Vrms 1kΩ
3.5Vrms 1.3kΩ
4.5Vrms 1.66kΩ
6.7Vrms 2.46kΩ
7.6Vrms 2.82kΩ
8.5Vrms 3.12kΩ
10Vrms 3.48kΩ
43Vrms 13.6kΩ
Note: unbalanced impedance about 30% less.
Frequency response: 5-180+kHz @ 32b/384kHz, depends on the interpolation filter setting
Linear phase fast low ripple filter 189kHz -3db, 180kHz -1db
SNR=DR@MONO:
127+/-1db(A) grade-B, 128-129db(A) grade-A, less than 126db(A) grade-C less than 125db(A)
STEREO mode has 3db worse SNR/DR. Measured at 32/48 AP2700
THD+N@1kHz@-.5dbFS SR48kHz BW 20-20kHz .00007%, SINAD less than 123db typical for grade-A, 122db grade-B
THD@1kHz@-.5dbFS BW 22-22kHz less than 0.00003%(.3-.2PPM) typical for 32b/48kHz all harmonics level -135-145db
Crosstalk: less than -140db@1kHz
E1DA Cosmos ADC


I bought an Altor Olivine-2 so that I could perform measurements using portable devices (laptop, Raspberry Pi). The noise floor is a little higher than the Asus sound cards, however the THD is slightly lower. It also has a physical volume control which is useful.
Another feature is that it's DC coupled - so you can use it as a DC voltmeter! (with care...)
It also features full USB isolation which is extremely useful too.
As of December 2020 the cost was $185
Specifications:
2 channels, 96/24 digitizing
Full galvanic isolation between USB digital part and ADC part.
Better then -135 dBFS Noise Floor
Better then -110 dBFS 2nd/3rd harmonics @0 dBFS signal.
Better then -135 dBFS 2nd/3rd harmonics @-20 dBFS signal.
UAC1 operation (not need driver for Windows) with firmware upgrade.
No external power supply need (USB-Powered).
Input level control potentiometer added.
0.5Vrms Full Scale (max., with potentiometer at right position)*
Power and Overload LED indication.
Small 120x75x30mm case (Depth-Width-Height).
* - changes since April 2019: Full Scale increased to 0.8Vrms, input is DC-coupled.
Altor Audio Olivine-2


The Scarlett 2i2 is a good interface, however it's not really suitable for very low noise / THD measurements. It's ideal for testing power amplifiers and speakers (in particular speakers, thanks to the phantom power for a good mic).
I believe that the gen3 version doesn't measure as good as the gen2.
Specifications:
Line inputs:
Dynamic Range: 106 .dB .(A-weighted)
Frequency Response: 20 Hz to 20 kHz, ±0.1 .dB
THD+N: less than 0.003% (minimum .gain, -1dBFS .input with
22 Hz/22 kHz bandpass filter)
Maximum .Input .Level: +22 dBu
Gain Range: 50 dB
Line outputs:
Dynamic Range: 106 .dB .(A-weighted)
Maximum Output Level: +10 dBu
THD+N Outputs (1-2): less than 0.002% (minimum .gain, -1 dBFS input 1 kHz, with 22 Hz/22 kHz bandpass filter)
FocusRite Scarlett 2i2 (this links to the current version)


Another good card from Asus - the Xonar DX. This is a little more basic than the Essence STX - however the spec is often better than quoted by Asus. The D2 version of this card (PCI) was used as a demo for RMAA - details here:
https://audio.rightmark.org/download.shtml
Specifications:
Output Signal-to-Noise Ratio (A-Weighted): 116 dB for Front-out
112dB for other channels
Input Signal-to-Noise Ratio (A-Weighted): 112dB
Output Total Harmonic Distortion + Noise at 1kHz (-3dB): 0.00056% (-105dB) for Front-out
Input Total Harmonic Distortion + Noise at 1kHz (-3dB): 0.0004% (-108dB) for Line-in
Frequency Response (-3dB, 24-bit/96kHz input): below 10Hz to 48KHz Output
Output/Input Full-Scale Voltage: 2 Vrms (5.65 Vp-p)
Asus Xonar DX


The Xonar Essence STX is an exceptionally good sound card and the ADC is very good too. This is one of the cards I use for my measurements.
Specifications:
Output Signal-to-Noise Ratio (A-Weighted): 124dB for Front-out
110dB for Headphone-out
Input Signal-to-Noise Ratio (A-Weighted): 118dB
Output Total Harmonic Distortion + Noise at 1kHz (-3dB): 0.0003% (-110dB) for Front-out
0.001% (-100dB) for Headphone-out
Input Total Harmonic Distortion + Noise at 1kHz (-3dB): 0.0002% (-113dB) for Line-In
Frequency Response (-3dB, 24-bit/96kHz input): below 10Hz to 90kHz
Output/Input Full-Scale Voltage: 2 Vrms (5.65Vp-p)
Headphone Impedance: Optimized for 32~600ohms
Asus Xonar Essence STX (link is to STX II)


I have no experience of this analyser, however I know they are quite well rated in the DIY community. The QA401 is no longer available, and has been replaced by the QA402.
This analysers are provided with their own software as well.
QuantAsylum QA401

Latest version...

As above but newer version...
QuantAsylum QA402

NOTE: I'm aware there are a lot of other hardware options out there. If you would like to submit any suggestions, please email me so that I can include them in this page.
Thanks.