Measuring the ADC output of a sound card
Hi,
I am fiddling with a new sound card, and am wondering if there is a bit of _Windows_ software which will read the output of a standard audio device, and present the data directly? You can almost do this by looking at an FFT display, and looking for clipping, but I was looking for a more direct, and quantifiable reading. Programs using AE4JY's DLL core will tell you when you are overdriving it, but that is pass/fail.
73s,
Alan WA4SCA
The data you get is PCM, you cannot *really* tell if it's clipped but you can measure the received amplitude and determine whether it's close to the maximum possible. In a new program I am writing I show this info. The overload value in DLLCore is something like 90% of the maximum peak signal which can be returned (I can look at the source if needed).
Can you explain exactly what you want to do and what you want to see?
Simon Brown, HB9DRV
----- Original Message ----- From: "Alan P. Biddle" APBIDDLE@mailaps.org
I am fiddling with a new sound card, and am wondering if there is a bit of _Windows_ software which will read the output of a standard audio device, and present the data directly? You can almost do this by looking at an FFT display, and looking for clipping, but I was looking for a more direct, and quantifiable reading. Programs using AE4JY's DLL core will tell you when you are overdriving it, but that is pass/fail.
Simon,
What brought this question about is a test with a new soundcard, a SignaLink USB. It have noticed that it is somewhat less sensitive than some previous cards I have used, which readily saturated unless I reduced the signal input. The SignaLink USB does not saturate, even at full gain, in the same application, which raises the question of whether I have enough signal. There are some issues which can be in the programs and CODECS, which is why I was wondering about something which gives you the raw ADC data.
From eyeballing the dynamic spectrum in MixW, I can get a rough estimate,
and it appears to be "good enough," in that I am not throwing away too much dynamic range. It isn't an important question, but it did seem worth asking if there was an existing program which would do this.
Alan WA4SCA
On Jul 28, 2007, at 7:03 PM, Alan P. Biddle wrote:
Simon,
What brought this question about is a test with a new soundcard, a SignaLink USB. It have noticed that it is somewhat less sensitive than some previous cards I have used, which readily saturated unless I reduced the signal input. The SignaLink USB does not saturate, even at full gain, in the same application, which raises the question of whether I have enough signal. There are some issues which can be in the programs and CODECS, which is why I was wondering about something which gives you the raw ADC data.
You actually got one? My two have been on order since April, and nothing but a postcard saying they were "having trouble getting their aluminum boxes" from their supplier.
I don't think that's the whole story -- hundreds of places will make custom aluminum.
If you just received that unit, perhaps you (and others) should compare the guts of an older one with a newer one. Especially if other reports of odd level issues start to show up.
If you have had it a while, disregard...
-- Nate Duehr, WY0X nate@natetech.com
Nate and others,
Brand new, out of the box Friday, though UPS said it was scheduled today, Monday. The PCB has a 2006 revision date on it, but lacking an older one, I can't do any comparisons.
Thanks to those who responded to my question. Using a combination of answers, and software, I was able to determine what I needed to know. It turns out that it is running about 85% of "full scale," which of course is an excellent match.
Alan WA4SCA
Alan P. Biddle wrote:
Nate and others,
Brand new, out of the box Friday, though UPS said it was scheduled today, Monday. The PCB has a 2006 revision date on it, but lacking an older one, I can't do any comparisons.
Sounds like my worries are probably unfounded then.
Looking forward to seeing mine "soon" since I was told "your order is one of the oldest"... when I called just prior to the ARRL June VHF contest.
Thanks to those who responded to my question. Using a combination of answers, and software, I was able to determine what I needed to know. It turns out that it is running about 85% of "full scale," which of course is an excellent match.
Glad she's workin' for you. Sure looked like a good unit, but this 3+ month wait for two units to arrive sure has me thinking I'll never order from TigerTronics ever again...
Of course, good products trump all sorts of shipping delays and bad customer service, when many other products simply don't have the features that one does...
We shall see if anything ever arrives in the mail...
Nate WY0X
Hi Alan,
Alan P. Biddle wrote:
... I am fiddling with a new sound card, and am wondering if there is a bit of _Windows_ software which will read the output of a standard audio device, and present the data directly? ...
The program Audacity (http://audacity.sourceforge.net/), which is multi-platform, will probably be the answer to this problem. We (the OZ7SAT crew) have used Audacity to decode the CW telemetry from CAPE-1, amongst other things, so we are very satisfied with it. You will see e.g. clipping easily.
Best 73 de Bent/OZ6BL
Thanks for the pointer. I will take a look. In any case, I can do this the old fashioned way, with a 'scope.
Alan WA4SCA
participants (5)
-
Alan P. Biddle -
Alan P. Biddle -
Bent, OZ6BL -
Nate Duehr -
Simon Brown (HB9DRV)