Audio Myths

2010 February 9
by Simba

Now, this may be only remotely relevant to tango, but tango music and hence its reproduction is important for dancers and djs in particular, so here it goes. I think the lessons from this video are most relevant when it comes to making decisions about equipment such as sound cards for djing, lossless versus lossy encoding of music and quality of transfers and restorations.

If you hang out at hydrogenaudio, this will all be familiar, but I have to say actually performing an abx was a humbling experience with regards to what I can and can’t hear. I really lost all confidence in the audio equipment pushers when I returned a radio with a really annoying high frequency noise and the guys in the store found nothing wrong with it, then gave me another one with the exact same problem… And I don’t claim to have golden ears.

People around the web and other places frequently make completely nonsensical statements about mp3 files and vinyl versus cd sound, which makes me somewhat skeptical to reviews of the quality of various transfers and restorations. Do they really know what they are talking about? Especially when you realize that just a small increase in volume will make the music ‘sound better’. More on that in a later post.

Some maybe surprising results when taking a scientific approach to sound quality:

Q: Is digital sound really better than vinyl?: A: Yes. Yes, really. We are talking orders of magnitude less distortion.

Q: Is playing from cds better than playing from a pc? A: No. If there is a difference, it is most likely in favor of the pc, which is both more practical and more reliable.

Q: Do I need to buy an expensive sound card to dj?: A:No. Even the cheap on board ones are usually very good these days. If you want to prelisten, you can get a usb headset.

Q: Do I have to use lossless files for djing?:  A: No. At reasonable bitrates, most people will never notice. Do an ABX test if you believe otherwise. If you are doing dsp, having the original is much better, and there are practical reasons for archiving using lossless audio)

Of course the trouble with tango is that we get the worst of all worlds, first shellac/78 distortions, then transferred to LP adding additional distortion, then possibly converting to mp3, then your music is subject to the lousy acoustics of the milonga/practica. Of which the least significant degradation is the mp3 conversion unless you choose ridiculously low bitrates. (mp3 gives good results around 128kbps and is found to be generally transparent around 192kbps,  somewhat lower for golden age tango music which is mono with low fidelity).

3 Responses leave one →
  1. 2010 March 1

    While there is a lot of snake oil in audio, it is very dangerous to say that all onboard cards are decent. This is simply not true for multiple reasons.

    First and foremost, most of them are awful at dealing with clipping or hickups in delivering sound/bits to the DAC. This means that your entire audience is prone to getting a clip and “bzzt” while they are dancing, or, even, in between dances. While this may not be terrible relevant if you’re not doing anything, if you use software to pull up a bit the sound to level it out, it can happen specially if you’re not using a compressor that takes care of clipping.

    On the other hand, the quality of hte connectors in laptops is appaling. The slightest touch may cause the jack to unconnect. A decent external soundcard will have decent regular jack plugs that will be much better. I’ve seen it happen, it sucks.

    The soundcards inside laptop are inherently noisy because they are not isolated from the computer’s motherboard, video card, etc. It’s simply the least of the manufacturer’s worries so the design is not buffered from all kind of crap from everywhere. This will cause the traditional low humming, buzzing that even becomes more obvious if you move your mouse or moving around in itunes, etc.

    Having used multiple generations of soundcards, I can assure you that not all soundcards are the same. The truth is, most of them are roughly the same as far as the DAC. In terms of pre’s and ADCs, the difference is HUGE but unless you’re getting stuff from vinyl or recording for fun, it’s irrelevant for DJs.

    I would say that if you’re shooting for mp3, there’s no reason for going with less than 256k. There’s not a space issue anymore and why compromise with lower quality bitrate? I don’t believe I know anyone that can tell the difference between a 256k mp3 and a CD too.

  2. 2010 March 2

    Usually with recent hardware, the playback quality is more than good enough. Of course, you will have to listen or measure to be sure. My previous laptop was horrible, the one I got now is good, and I helped a friend set up his new pc, where the sound was excellent. The problems you mention have largely been solved with current hardware in my experience. (I still use an external myself because I have one and need two cards to prelisten, though.)

    Recording is a different matter entirely.

    With respect to mp3 bitrate, I don’t see the point with 256k and higher, as that is close to the lossless bitrates of the typical golden age material. Space is still an issue with portable devices, I am just moving (ironically) to lossless because my laptop doesn’t have room for my collection in lossy format anymore, and with all the space on the external disc I have to use I may as well go lossless.

  3. 2010 March 2

    In the scientific spirit of this post, I just did some measurements on the internal card of my three-year-old laptop (which I claimed was ‘good’). I used the Right Mark Audio Analyzer, which can be downloaded for free. Here are the results:

    Frequency response (from 40 Hz to 15 kHz), dB +0.05, -0.02 Excellent
    Noise level, dB (A) -82.6 Good
    Dynamic range, dB (A) 82.9 Good
    THD, % 0.0088 Very good
    THD + Noise, dB (A) -76.1 Average
    IMD + Noise, % 0.019 Very good
    Stereo crosstalk, dB -84.9 Very good
    IMD at 10 kHz, % 0.021 Good
    General performance Very good

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