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Discussion Starter #1
Hi !

I'm used to run REW for quite long sessions, and after a certain time different kinds of problems appear with the signal generator :
1. At the end of the sweeps, apparition of strange sounds like echoes.
2. When using a continuous sine signal, production of a very distorted one, see the picture :



3. I wanted to make spectrum measurements of a loudspeaker at 3 kHz, exactly spaced 10 dB (0,01W, 0,1W, 1W and 10W). Hereunder the four measurements :









The peak values of the fundamental are respectively 124,8 dB, 135,4 dB, 141,1 dB and 153,9 dB (uncalibrated microphone), then not regularly spaced.

When I see any of these problems, I close and reopen REW, and everything is in order again.
Is there anything pertinent to do ?

Regards

Pascal
 

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Perhaps a problem with the soundcard driver or OS resampling. Are you using Java or ASIO drivers? Does the sample rate in REW match the rate in the Windows audio properties for the card?
 

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Discussion Starter #3
Hi John !

The soundcard I'm currently using is the Steinberg UR22, which is a medium quality soundcard, probably.
The driver I used yesterday was JAVA, with 48kHz sampling rate.
Tonight I tried to compare the results with ASIO and JAVA drivers, using a continuous 3 kHz sine signal and examining the spectra produced by the soundcard running stand alone.
The measurements have been made at -5, -15, -25 and -35 dB levels.

In the attached PDF, you can see that :
For -5 dB (high level), the spectra are almost identical, maybe JAVA is a little bit better.
For -15 dB, ASIO becomes a bit better
For low levels (-25 and -35 dB), ASIO gives far better distortion results, harmonics being nearly totally mingled with noise.

It seems to be a good indication of what to look at, and I will make new measurements in that ASIO configuration.

Pascal
 

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Bear in mind the Java driver passes 16 bit data to the soundcard, so should really set dither to 16 bits for the Java driver.
 
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