Audio Test Set (eg Lindos) alternatives
« on: March 03, 2019, 08:09:03 PM »
Hi,

I'm considering a build that has quite a bit of calibration required at the end and the guide says audio test set (eg Neutrik / Audio Precision / Lindos) is required.

This is obviously a very expensive item to purchase if I may not need it again, and I may as well just buy the item rather than try to build it.  Is there a cheeper way to achieve the kind of thing I need to do?  It looks like it is applying signal at a known dBu value, and reading levels back at the output.  Also measuring TH+D and power supply ripple.

If I don't already have this equipment, am I just fooling myself with considering a build like this?  I'm confident I can construct the board, but obviously that's not the whole task!

Advice please.
Thanks


squarewave

Re: Audio Test Set (eg Lindos) alternatives
« Reply #1 on: March 03, 2019, 09:14:01 PM »
The noise floor of a conventional USB audio interface will be below the theoretical noise of a small resistor. So there really is almost no reason to use fancy hardware anymore. Maybe for calibration or if it has good attenuation / amplification for optimizing levels around the DUT. But attenuation is usually easy and frequently you have to make cables for the DUT in which case you can integrate attenuation into the cable (such as for a mic pre for example you can put a 150K:150R directly into the XLR).

The important component now is software. I actually don't love any of the audio analyzer software packages out there. But maybe that is because I refuse to spend money on it. Personally I just use GNU Octave which is the open source corollary of Matlab which is a declarative language interpreter for performing various, potentially very sophisticated, mathematical transformations on arbitrary data. For audio, I just create a recording and then use Octave to generate hi-res spectra. Most people just use something like Room Eq Wizard. At one point I was using something called DSSF3 from ymec.com (although I think that actually costs a little money).

But your question is a little vague. If you can share more about what you ultimately want to test, the answers to your question will be better.

Gold

Re: Audio Test Set (eg Lindos) alternatives
« Reply #2 on: March 03, 2019, 09:55:20 PM »
Yes there are cheaper ways of doing it.  An audio interface with some shareware will do it.

The only snag is you have to know what you are doing to set it up properly and be able to trust the results. The thing about a dedicated test instrument is that it’s calibrated and you can trust the results.

abbey road d enfer

Re: Audio Test Set (eg Lindos) alternatives
« Reply #3 on: March 23, 2019, 04:19:51 AM »
I would recommend looking ar RMAA (Right Mark Audio Analyser); it's free, it's simple to use. Now, as others have mentioned, ther's the issue of calibration. You need a good meter, with a frequency response that allows proper checking of 1kHz signals. Almost any serious multimeter can do that now.
I would also recommend you install a virtual oscilloscope; that one is pretty good: http://www.sillanumsoft.org/download.htm
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


 

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