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I have a Sound Blaster X-Fi Xtreme Audio Notebook sound card and I was measuring its output frequency using frequency counter connected to the card's output. Frequency was generated using a program called FrequencyGenerator. I've noticed that it can't provide frequencies higher than 16 kHz (upper limit of audible range is at 20 kHz) and I found that strange.

Is there any info on common maximum frequencies provided by sound cards? I know that for example Realtek ALC 268 can provide as much as 19500 Hz (which is pretty close to the needed 20 kHz), but since X-Fi is supposed to be better than average integrated sound card, is are ALC 268's capabilities an exception or is the X-Fi just really bad card (as in has low output spectrum)?

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Are you talking about the sound card only or also about the speakers or headphones you're using? –  slhck Jan 26 '11 at 22:27
    
@slhck Meter was connected directly to sound card's output, so just sound card. I expect that speakers/headphones and similar devices do have their own limitations. –  AndrejaKo Jan 26 '11 at 22:29
    
It's going to depend on the chips that the card uses, so you'd have to do a search for each cards specs. However, I would expect the upper range to be < 20 kHz. –  ChrisF Jan 26 '11 at 22:32
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What is your sound source? Please don't say MP3, which are limited to 16khz. –  mtone Jan 26 '11 at 22:34
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I would have thought ≈20 kHz (as per the Realtek spec), but I've no evidence for this. –  ChrisF Jan 26 '11 at 22:36
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1 Answer

up vote 1 down vote accepted

Here's Rightmark benchmarking results (PDF) for the X-FI. On page 15, their results using a loopback (output cable plugged into line-in and recording) indicate a relatively even frequency response up until 20khz and beyond.

This testing technique has the advantage of excluding the speaker from the testing, but the drawback is being limited on the input capabilities, which can have lower specs. The X-FI is rated for both playback and recording at 24bit/96khz

Don't forget that MP3s are stripped of frequency range above 16khz so that is not a test source to use. Ideally, use a software sine wave generator.

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You're interpreting the 48 kHz incorrectly. It isn't the maximum frequency card can provide, it's the number of times the card generates output in a second. Digital computers can't generate continuous signals, so they quickly generate large numbers of discrete signals which to our imperfect senses look continuous. –  AndrejaKo Jan 26 '11 at 22:49
    
I'd also like to note that the results are for classic real X-Fi cards. Some cards X-Fi cards like Sound Blaster X-Fi Xtreme Audio Notebook and Xtreme Audio only have X-Fi brand and do not have EMU20K1/EMU20K2 chips from the real X-FI cards. Still, good answer! I'm looking for more answers like this one. –  AndrejaKo Jan 26 '11 at 22:54
    
@AndrejaKo, sorry, what part of my answer are you replying to? (I removed the 48khz recording limit part because that was for the previous generation, Audigy I think) –  mtone Jan 26 '11 at 22:56
    
The first comment was about the original answer which mentioned that X-Fi has 24bit/48kHz and that 20 kHz should be in that range. I interpreted that as, maybe incorrectly, that if 20 kHz is less than 48 kHz, it should be playable. The second comment is just that, a comment clarifying the linked paper. I'm saying that is isn't really useful with my specific card, but is otherwise great answer which provides what I'm looking for. –  AndrejaKo Jan 26 '11 at 23:00
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@AndrejaKo Interesting, I did somehow believe that the rated frequency would match what the card can output, or near half of it if there's a filter at the nyquist frequency. But I guess if that was the case, you wouldn't have asked this question. Thanks for the insight. –  mtone Jan 26 '11 at 23:08
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