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S-Sound distortion - what causes it?
slks
post Jun 6 2012, 09:15
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This was originally going to be a reply to another topic, but I thought I'd make a new one instead of derailing someone else's. (In case you were wondering why I'm starting in the middle of things and seemingly pulling quotes from thin air!)

QUOTE (jamie_P84 @ Jan 25 2011, 18:19) *
QUOTE (ramicio @ Jan 25 2011, 20:22) *
One thing I noticed with this turntable is with newer records you will get horrible distortion whenever a microphone-kissing artist makes a hard sound like S, F, or T.


In my own collection, all the records made from 1979 onwards are digitally-sourced (apparently due to the introduction of digital cutting delays in the mastering chain). I only bother with vinyl if it was produced prior to this date.


I think that's a rather misguided notion, and here's why -

I've got original pressings of Elton John and Kinks albums (among others) from the 60s and 70s that have this "S"-sound distortion, that also occurs on certain cymbal hits, usually hi-hats. It's very ugly. (Some of my old records are fine, though.)

I also have albums that have been written, recorded and pressed in the digital age, many from the last few years (2008 - 2011). None of them have this distortion.

The newer records were all bought new by me, and have been in my sole possession. The older ones changed hands God knows how many times before they ended up in my collection. This leads me to believe that the S-sound distortion comes from the records being damaged in some way - played on bad/misconfigured equipment, maybe something like the tracking force or stylus angle being grossly off from what it should be? Maybe simply from being played too many times?

I've been wondering since I started collecting what causes records to become distorted in this way. So if someone who knows what they're talking about could tell me, definitively, what causes this type of distortion, I would be very grateful.


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bug80
post Jun 6 2012, 12:02
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What also could be a reason is that most studios nowadays use "de-essers" when recording or during mixing. It depends on the singer if such processing is necessary, for some vocalists / microphone combinations the "S-distortion" can be quite severe if you do nothing about it.
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Fedot L
post Jun 6 2012, 20:35
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QUOTE (slks @ Jun 6 2012, 09:15) *
S-Sound distortion - what causes it?

Non-linear distortions in the signal path.
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cliveb
post Jun 7 2012, 08:22
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QUOTE (slks @ Jun 6 2012, 09:15) *
I've been wondering since I started collecting what causes records to become distorted in this way. So if someone who knows what they're talking about could tell me, definitively, what causes this type of distortion, I would be very grateful.

Since you're only hearing this distortion on secondhand LPs, the overwhelming liklihood is that it is groove damage caused by previous mistracking. Mistracking happens when the cartridge setup is wrong (geometry, tracking force, anti-skating, or any combination of the three) and/or the pickup arm bearings are sub-standard and/or the cartridge simply isn't good enough. Many (most?) inexpensive turntables exhibit some degree of mistracking, and when it happens, the stylus loses contact with the groove wall and bounces around uncontrollably, in the process gouging fragments out of the groove wall and thereby damaging it permanently.
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dhromed
post Jun 7 2012, 09:37
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QUOTE (cliveb @ Jun 7 2012, 09:22) *
when it happens, the stylus loses contact with the groove wall and bounces around uncontrollably, in the process gouging fragments out of the groove wall and thereby damaging it permanently.


That sounds a little dramatic, conjuring images of scraps of vinyl and sparks flying with every play, or using a potato knife instead of a stylus. What sort of fragment sizes are we talking about?
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cliveb
post Jun 7 2012, 10:49
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QUOTE (dhromed @ Jun 7 2012, 09:37) *
QUOTE (cliveb @ Jun 7 2012, 09:22) *
when it happens, the stylus loses contact with the groove wall and bounces around uncontrollably, in the process gouging fragments out of the groove wall and thereby damaging it permanently.


That sounds a little dramatic, conjuring images of scraps of vinyl and sparks flying with every play, or using a potato knife instead of a stylus. What sort of fragment sizes are we talking about?

Probably sub-micro sized. In other words, minuscule on a human scale, but LP playback works on a very small scale (a quick back-of-envelope calculation suggests that signals down at -60dB involve groove wall deflections of about 0.0001mm - ie. 1/10th of a micron).

And on reflection I probably misrepresented the nature of the damage. Rather than bits of vinyl actually being removed, the damage is more usually permanent deformation of the groove wall (due to plasticity). Try to imagine what will happen if you take something very hard (ie. diamond) and bash it against something soft (ie. vinyl). You're going to make lots of dents and scrapes, and sometimes you might knock a little bit of material away. That's what the stylus does to the groove wall during mistracking.

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