I am experimenting with an Instek oscilloscope. I have two sources. One is an audio output from the laptop, and another one is a tone output from a function generator.
This is a video of the laptop output:
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This is video of the function generator output:
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I just terminate the sources to a 1k-ohm resistor and put the oscilloscope probes across the resistor.
Are laptop audio outputs really that "poppy" (intermittent signal spikes)?
When I plug in a headphone to the output jack of the laptop, the tone sounds clean. I was expecting to hear tiny pops.
If I were to take the laptop audio signal and re-route it to a different circuit, how would I make the waveform "cleaner" like the one from the function generator output?
I'm afraid that if I take the audio output of the laptop and connect it to an amplifier, then the spikes will also get amplified and become noticeable.
Laptop audio outputs are all over the place ... in my experience ... some OK, some very marginal. Your ear will miss some things that a scope will see. You could use a filter with the laptop to clean up the waveform.
I find that in many PC's and Laptops, the sound systems DAC/ADC is very poor for precise work. The different venders for sound systems vary in what they use (approximation or absolute) encoders/decoders. Using FFT's (DFT's) works well in removing many of the artifacts from poorly design discrete components, but not all of it. The last professional sounds system I saw via a PC, didn't even use a well known high end sound card that one would expect. They were using stand alone ADC's and DAC's with additional digital audio interfaces.
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Sorry, I can't view your example (dial-up connection too slow!). However, even the crappiest laptop chipset should not have intermittent signal spikes. This sounds (no pun intended) like a software problem. Is the software trying to generate a signal by simply playing one cycle over and over?
You are welcome to download Daqarta for Windows and use the built-in signal generator. If you still have problems, (though I'm betting you won't) *then* you can blame the sound card. The Daqarta generator is free to use forever... no need to purchase if you don't need to monitor input signals.
A new version with lots of improvements and bug fixes is going to be released Monday (I hope!), but if you can't wait you can install the current version now and the new one will install easily over it. One of the problems with the current version is that many users say it immediately reports that the trial period is expired, so you can't try the input functions. That won't affect your using the function generator, but it will prevent you from using the built-in auto-calibration system to calibrate the sound card attenuators. You should do that with the new version before the trial expires, and the calibration will be retained.
Enjoy!
Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis
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Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!
The old DaqGen (just the signal generator portion of Daqarta as a stand-alone program) had problems with some video accelerators, which could be fixed by reducing the video acceleration settings in Windows Control Panel. I haven't noticed or heard of that with Daqarta for Windows, but that could be simply due to newer video systems finally having their act together. Might be worth a quick test with Control Panel.
Best regards,
Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis
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Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!
Following up on the above: There is actually a dead-simple test: While the sound is running in Daqarta, hit the Pause button to stop the display, but not the sound. If the problem goes away, you can be pretty sure that it was a graphics acclerator problem. I just checked the upcoming Daqarta version on my old 200 MHz Win95 system, and it does indeed have a stuttering problem at max acceleration. (In fact, I had long ago set it back to "Basic Acceleration" to solve this problem on an earlier version. No change in graphics performance that I could see, though I'm not a gamer.)
To change the setting in Win9x, go to Start - Settings - Control Panel - Display - Settings - Advanced Properties - Performance. Set the Harware Acceleration slider over to one position from the left, which will say "Basic Acceleration".
On WinXP I've never seen any problems even at max acceleration, but the procedure is pretty much like above: Start - Control Panel - Display - Settings - Advanced Once you click Advanced, things get more iffy. The system I just checked had hardware acceleration under Troubleshoot, which is *not* the same Troubleshoot you see on the Settings page.
The reason for the conflict, especially on older systems, was that graphics card makers often released a "no holds barred" ultimate performance driver that locked out other system processes in order to squeeze the highest *graphics* performance ranking in reviews. Then after people bought the cards and found (too late!) that they had these other problems, the card maker could release a driver upgrade that toned down the performance a smidgeon but played nicely with everybody else.
So if you have sound problems, and you find graphics too slow for gaming or whatever using Basic Acceleration, check on the Web for a driver upgrade for your graphics card.
Best regards,
Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis
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Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!
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