Experiences with software thd, sine generating - diyAudio
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Old 25th December 2014, 09:13 AM   #1
hahfran is offline hahfran  Germany
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Default Experiences with software thd, sine generating

anyone?
I don't have neither a ultra low thd sine gen nor a precise thd analyser. I have a very old Terratec soundcard which has a wavetable for sine gen and a 24bit/192 kHz sample Julia soundcard. Any hint, experiences, software very appreciated.
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Old 25th December 2014, 09:19 AM   #2
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Rightmark Audio Analyzer is a popular program for measuring THD. Be warned that a good DIY audio amp will perform better than most soundcards.
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Old 25th December 2014, 10:02 AM   #3
hahfran is offline hahfran  Germany
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Thanx..priced in Ruble... should cost almost nothing these days...
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Old 25th December 2014, 11:37 AM   #4
hahfran is offline hahfran  Germany
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Looks like a simple spectrum analyzer software is not less reliable...
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Old 25th December 2014, 12:45 PM   #5
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There's nothing poor about the Juli@ soundcard. It's probably still up with current cards and certainly the connector quality and construction are superior to most others. The problem is cost and complexity of presentation quality software. Most is aimed at studio use and good products like ARTA are not so cheap to buy, whatever the number of features. It's still a great, comprehensive combination for a soundcard.

Quantasylum QA 400 USB card package is focused on distortion measurement but cheaper and simpler to install and get results fast: QuantAsylum QA400

Unfortunately all souncards lack a suitable wideband precision interface for measuring power amplifiers. You can build one (Member Pete Millet markets a PCB/panel label kit) but there aren't many you can buy simply or cheaply.
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Old 25th December 2014, 02:44 PM   #6
hahfran is offline hahfran  Germany
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I think a freeware spectrum analyzer software provided it interfaces to Juli@ drivers would do as an indicative tool, the key to success will be an interface, preferably battery operated, and even more preferably, transformer coupled . But that is already another, say, "dark matter" those audio transformers.
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Old 25th December 2014, 08:28 PM   #7
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I use the German software from >HERE<, commercial version. With Lynx L22 pro-grade sound card - very precise metering system. External loopback shows THD at the level of 0.0001% at 1KHz as well as at 20KHz (see attached). Output level is 650mV RMS here, sample rate = 192KHz.

Software looks inexpensive comparing to what the Lynx card costs
I love it

Cheers,
Valery
Attached Images
File Type: jpg 04-THD-01KHz-LB.JPG (191.0 KB, 219 views)
File Type: jpg 04-THD-20KHz-LB.JPG (188.5 KB, 214 views)
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Old 26th December 2014, 07:28 AM   #8
hahfran is offline hahfran  Germany
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vzaichenko thanx. Lynx is for professionals my objective is just an amp/speaker/listening room system for my own use. Thus the Juli@ card must do - otherwise I could just buy an active monitor speaker e.g. from JBL. I think only very few diy amp plus diy speakers could trump such an active monitor for around 1200 USD a pair.
However I would not trust any sort of a "precision" claim as the interior of a PC is electrically incredibly noisy. The , say, vintage Terratec card targeted at musicians - professional demo recording - came completely metal shielded.

Last edited by hahfran; 26th December 2014 at 07:39 AM.
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Old 27th December 2014, 04:00 AM   #9
djoffe is offline djoffe  United States
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I've been using the Behringer UCA202 Audio Interface (USB, so it sits outside the computer) along with the demo version of ARTA software.

ARTA Software

While not perfect, it's quite handy. Main thing it would need to take it to the next level is a precise stepped attenuator on the front end.

I'm sure there are better Audio interfaces, but this one was $30, and has RCA line level I/O, which is about the most useful for what I'm doing.

I'd certainly be happy to hear what other cards and software people are using.

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Old 27th December 2014, 07:04 AM   #10
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Quote:
Originally Posted by vzaichenko View Post
... software from >HERE<, commercial version. With Lynx L22 pro-grade sound card - very precise...
Hi Valery
The screen for the 20 kHz THD doesn't show any response past 20 kHz.
If the response is filtered past 20 kHz then the THD will look very impressive, of course
Some sound-cards and/or software assume you don't want response past 20 kHz.
Fine for sound but bad for measurement, have you checked this?
Can you show the response past 20 kHz?

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Last edited by Dave Zan; 27th December 2014 at 07:07 AM.
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