Comparison of laptop audio output and function generator

M

MRW

Guest
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:
http://video.google.com/videoplay?docid=-8413182111152350269&hl=en

This is video of the function generator output:
http://video.google.com/videoplay?docid=-3995690077431458348&hl=en

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.

Thanks!

M
 
"MRW" <mr.whatever@gmail.com> wrote in message
news:1190831539.138843.94910@g4g2000hsf.googlegroups.com...
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:
http://video.google.com/videoplay?docid=-8413182111152350269&hl=en

This is video of the function generator output:
http://video.google.com/videoplay?docid=-3995690077431458348&hl=en

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.
Click to expand...
The first link is not working for me. Sorry.

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.
 
Charles wrote:

"MRW" <mr.whatever@gmail.com> wrote in message
news:1190831539.138843.94910@g4g2000hsf.googlegroups.com...

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:
http://video.google.com/videoplay?docid=-8413182111152350269&hl=en

This is video of the function generator output:
http://video.google.com/videoplay?docid=-3995690077431458348&hl=en

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.


The first link is not working for me. Sorry.

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
Click to expand...
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.



--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
 
On Wed, 26 Sep 2007 11:32:19 -0700, MRW <mr.whatever@gmail.com> wrote:

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:
http://video.google.com/videoplay?docid=-8413182111152350269&hl=en

This is video of the function generator output:
http://video.google.com/videoplay?docid=-3995690077431458348&hl=en

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.
Click to expand...
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
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!
 
On Sep 27, 9:03 am, NoS...@daqarta.com (Bob Masta) wrote:
On Wed, 26 Sep 2007 11:32:19 -0700, MRW <mr.whate...@gmail.com> wrote:
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:
http://video.google.com/videoplay?docid=-8413182111152350269&hl=en

This is video of the function generator output:
http://video.google.com/videoplay?docid=-3995690077431458348&hl=en

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.

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
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!
Click to expand...

Hi Bob,

I'm actually using DAQARTA to generate the tones from the laptop. :)
I'm using an older version, though.

I'll see if I can take a picture of the signal when I have access to
the oscilloscope again.

Thanks!
 
On Thu, 27 Sep 2007 19:11:12 -0000, MRW <mr.whatever@gmail.com> wrote:

Hi Bob,

I'm actually using DAQARTA to generate the tones from the laptop. :)
I'm using an older version, though.

I'll see if I can take a picture of the signal when I have access to
the oscilloscope again.

Thanks!
Click to expand...
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
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!
 
On Fri, 28 Sep 2007 12:06:29 GMT, NoSpam@daqarta.com (Bob Masta)
wrote:

On Thu, 27 Sep 2007 19:11:12 -0000, MRW <mr.whatever@gmail.com> wrote:

Hi Bob,

I'm actually using DAQARTA to generate the tones from the laptop. :)
I'm using an older version, though.

I'll see if I can take a picture of the signal when I have access to
the oscilloscope again.

Thanks!


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.
Click to expand...
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
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!
 
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