November 03, 2014

Digital mythbusting

No, analog music playback technology isn't "better" than digital. Dylan Matthews points out in Vox that the "warmness" of vinyl is a byproduct of the noise, bandwidth limitations, and mechanical dampening that playing a record involves.

A record needle is shaken back and forth many thousands of times a second to produce a piezoelectric or electromagnetic signal (it's a little electrical generator). Without artificial filtering known as "RIAA equalization," the needle would jump all over the record.

Add to that the noise produced by the motor and bearings spinning the record. "Vinyl" reproduces music by dragging a needle down a groove of serrated plastic. Okay, not fingernails across a blackboard but the same basic concept. It's amazing that it works as well as it does.

The same audio illusion is promulgated by vacuum tube amplifier buffs. The "warmness" of a vacuum tube circuit is a byproduct of the electrical noise (hum) and dampening that are an inevitably byproduct of the electronics and can never be eliminated.

Even with expensively-filtered filament current, you can never get rid of the thermal noise. Isolating the plate voltage (to keep the listener from being electrocuted) requires big transformers that also effectively filter out any high-frequency overtones.

I'm totally down with the assertion that it makes for a great sound, but there's nothing "natural" about it. (The same goes for "organic" food.) As Matthews puts it, "[Vinyl and digital] sound different, and that's exactly the point."

Christopher Montgomery explores in more rigorous scientific terms what Matthews is saying (and shows why Matthews had to correct his article to state that digital recordings do, in fact, replicate the whole audio wave). "Better" digital quality often isn't:

Neither audio transducers nor power amplifiers are free of distortion, and distortion tends to increase rapidly at the lowest and highest frequencies. If the same transducer reproduces ultrasonics along with audible content, any nonlinearity will shift some of the ultrasonic content down into the audible range as an uncontrolled spray of intermodulation distortion products covering the entire audible spectrum.

The quality of digital converters does make a difference, and have improved dramatically in the past decade. But just as a professional can take a good picture with a cheap camera and high-end equipment won't help a talentless amateur, the human element matters a lot.

The human element is really what this whole debate comes down to. Stuart Andrews pops a hole in the balloon of our sunk cost-inflated egos. At the end of the day, what investing the big bucks in high-quality MP3 players and headphones can really do is

give you more convincing arguments as to why one version sounded better than the other. In effect, they had better tools with which to convince themselves that their subjective impressions were correct, even when those impressions were entirely misleading.

Convince people to pay more for an object with the same performance specs and they'll value it more because of the sunk costs, the replacement costs, the invested self-image, and the good opinion of their fellow devotees. This is otherwise known as Apple's business plan.

And, yes, it's also true that the price/quality curve is generally positive. Though when it comes to modern electronics, the curve flattens out much closer to the low end than to the high end. Which is why you can get a decent LCD HDTV for $120.

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# posted by Blogger Joe
11/03/2014 4:43 PM   
What cracks me up is the craze of lossless compression, which blithely ignores the fact that there are no A/D converters and speakers/headphones which have enough fidelity to make a difference.

Ten years ago, critics of MP3s had a small point--at the time most of the algorithms would clamp the lowest frequencies at 128 kbps. This is a big reason WMA sounded so much better at really low data rates. Since then, MP3 compression algorithms have improved immensely (helped by much faster CPUs and the SSE instruction sets) and those early restrictions were removed. I think WMA still has a slight edge at low data rates, but it's only slight.

(Speaking of digital. I stopped going to theaters for a while because I tired of watching bad flicker, uneven projection lighting, scratches and worn registration pins which caused the projected image to shake ever so slightly. Digital projection fixes all of that. Hurray for digital!

Now for the Boo for Digital! As in TV. First, there are some weird and very distracting strobing artifacts that seem to be really common, especially in high contrast and mostly live video feeds. The other problem is that if I get the slightest interference, due to rain, clouds or whatever, in the old days my image would get fuzzy, but I could still watch the show. Now, it gets blocky, pauses or goes away entirely.)