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Hardware and Sound cards for audio measurement

Hardware and Sound cards

Altor Audio Olivine-2 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 highger 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
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

FocusRite Scarlett 2i2 (2nd gen)

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.
Line inputs:
Dynamic Range: 106 .dB .(A-weighted)
Frequency Response: 20 Hz to 20 kHz, ±0.1 .dB
THD+N: <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): <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)

Asus Xonar DX

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:
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): <10Hz to 48KHzOutput
Output/Input Full-Scale Voltage: 2 Vrms (5.65 Vp-p)
Asus Xonar DX

Asus Xonar Essence STX

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.
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): <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)

QuantAsylum QA401 Audio Analyser

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...

QuantAsylum QA402 Audio Analyser

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.


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