Choice of new Distortion Analyzer

[phofman]

GitHub - dechamps/ASIO401: An unofficial ASIO driver for the QuantAsylum QA401 audio analyzer.

 

[jan.didden]

Thanks Pavel, that's good to know!

Jan

 

[vgeorge]

From the quantasylum site:

Finally, if you want to use the QA401 with your favorite ASIO-enabled audio analysis software such as ARTA or MATLAB, there's a 3rd party ASIO driver for the QA401 available on Github.

Releases * dechamps/ASIO401 * GitHub

I think that I did try it with success last year, but I use QA401 software mostly.

 

[trung224]

Like OP, I am building my personal test bench. I have a good DMM, a general purpose 20MHz function generator and a Textronic 2235 oscilloscope.

For THD measurment, I am considering two setup.
Set 1: QuantAsylum QA401 + Victor's oscillator
Set 2: Autoranger + distortion magnifier + good soundcard (EMU1212, which I can get cheaply) + Victor's oscillator

So, I would like to ask you folks which setup should I choose if I want to measure THD or THD+N of composite opamp circuit (AD797+AD811) or power amplifier.

Thanks,
Trung

 

[phofman]

I do not understand how people use an analog oscillator with drifting frequency in precise long-FFT/averaging measurements, using generic FFT softwares without some support for the drifting frequency.

 

[phofman]

So, I would like to ask you folks which setup should I choose if I want to measure THD or THD+N of composite opamp circuit (AD797+AD811)

I measured opamps THD using a regular soundcard + a bit of math a few days ago, IMO the measured values are comparable with those established by other methods https://www.diyaudio.com/forums/equ...nsation-measurement-setup-36.html#post6140955 . Only the latest ultra-low distortion opamp was below the method resolution threshold. IMO EMU1212 with a simple adapter (a $2 multiturn pot, one SPDT switch + simple OPA1656 buffer) and the open-source software would measure your opamp combination too.

 

[kevinkr]

Remarks on noise was generics : when measuring very low level signals, intrinsec or environnement noise can limit floor level.

Thanks for recalling me this model. I've already heard good feedbacks about it. Seems that problems identified today are recap and... find model with options

I have owned an Amber 3501a for 21 years and love it, that said I would not consider it a good choice for someone on a limited budget, the QA-401 or a similar computer solution is a lot more versatile, the bundled software is very good IMLE, and I seen to recall that there is an option to use it as a sound card for use with other software.

The 3501a is quite limited in its utility and it's performance while good is not cutting edge.

Note with a little work it is quite possible to get noise floors in the -120dBV range with a PC and USB based solution. (things like isolation transformer to provide power to the computer, isolated USB and similar all help.)