Thursday, February 14, 2013

Lousy Sound

I have noticed a trend -- lousy sound. I have been a music lover and audiophile (not audiophool, which is unscientific superstition, like anthropogenic climate change) since high school.

Listening to Pandora, I was struck by a new kind of distortion. It's an obnoxiousness in the upper midrange, almost like a harsh, noise modulation being kicked up by things like electric guitars and vocals. It isn't harmonic, and it isn't normal intermodulation. And no, it's not this.

What a long strange trip it's been, getting to the bottom of it. At first, I figured it was Pandora's standard AAC bitrate. So I paid for the subscription version so that I could get the high quality feeds. No joy. Besides, AAC actually sounds really good at reasonable bitrates.

So then I suspected my speakers. Maybe they were just obnoxious, so I started listening with headphones -- three different ones. No joy. Next was the sound card, so I tried a number of different ones on various machines I have at my disposal. They all exhibited the same obnoxiousness.

Heathkit AA-1214
Crossover distortion in my amplifier? I replaced the finals in it a while back, because they went into Vce breakdown and burned up. I used the original part, but with a higher breakdown voltage that wasn't available in 1972. Did I get the bias wrong? It turns out, one of the bias resistors had changed value. So I re-biased both channels. Distortion measurements are well within their original spec. Besides, this amp has never sounded bad to me in the 40 years since I first assembled it. The obnoxiousness persists.

My ears? Maybe... I do have tinnitus... but no, it doesn't happen on every song. I don't notice it with my old personal CD or vinyl collections (although the distortion does sound somewhat similar to vinyl damage from a worn out stylus). But I have been familiar with that phenomenon since the early '70s, when my ears were brilliant. Although I miss with great anguish the acuity of my youth, I do know how to listen. This ain't it.

To reiterate: it doesn't happen on every song. I have heard of the loudness wars that CD producers have been engaged in. It's the same idiotic loudness wars that broadcasters have been engaged in for many years, except it's even more idiotic when we're dealing with a medium that so doesn't need any additional processing to sound good. There's more than enough headroom on a CD for the dynamic range of any music known to humans. There's no reason to pack it all into the top 6 dB of the 96 dB available.

Not only do they compress the snot out of it, they clip it too. If this clipping occurs before the A/D converters, the higher harmonics that would cause aliasing get filtered out. But if they clip after the A/D converters, it will cause aliasing, and aliasing sounds nasty.

Aliasing has no correlation with the harmonic structure of the music (in fact, it's inverted). But it will kick up as noise whenever the digital clipping occurs. I can't imagine that recording engineers and record producers would be so stupid as to clip in the digital domain (without using the proper anti-aliasing filters), but maybe they do. If anybody knows, please drop me a line, or post a comment here.

I would not expect this obnoxiousness to occur with the classics, but with so many classics being remastered and reissued, I expect that the new releases of old material are also getting the same treatment. It certainly sounds like it is. Even our proud legacy is being mutilated.

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