How does anti shock work? compromises music?
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kenchi1983

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"By buffering the sound, you're actually listening to whatever was being scanned 40-seconds ago (at least that's how I think it works)"


Found in amazon from portable cd reviewer. so is this true? because it sounds logical.


Just bought a jvc brand pcdp......hmmmm, im not even sure if its good since i cant find much reviews on jvc products. And almost everyone here either uses pana or sony. I could go for these brands, but since im only going for the budjet pcdp, i dont think theres much difference in sound output. Hope i made a good purchase.


http://www.amazon.com/exec/obidos/AS...115616-4523849

How about philips? a guy just went to me a recommended the philip brand--and he said philip was the inventor of cds. I went with my instincts though and chose jvc.
 
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Quote:

Originally posted by kenchi1983
"By buffering the sound, you're actually listening to whatever was being scanned 40-seconds ago (at least that's how I think it works)"


Wouldn't that mean that startup would take 40 seconds?

I was also wondering how anti-shock supposedly affects sound.
 
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MacDEF

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Quote:

Originally posted by sapphiremodena
Wouldn't that mean that startup would take 40 seconds?


No, because the CDP can fill the buffer at a faster rate than the DAC draws data from the buffer for audio output. The instant you press the play button, there is zero data in the buffer; after a bit of time has passed, the music is playing, and the buffer has only partly filled. After some period of time (which varies depending on the CDP) the buffer fills completely.

At that point, the output is *always* drawn from the buffer and *never* from reading the CD itself. As data is read from the buffer by the DAC for audio output, a commensurate ammount data is read off of the CD to replace it.


How this affects audio quality depends on the type of buffer used. Since 1 second of uncompresed CD audio takes 300-400k of memory, 40 seconds of shock protection would take 12-16MB of onboard RAM (these are estimates, by the way, used for illustration). To keep costs down, and battery life longer, most portables only include 2-4MB of RAM. That means that in order to have 40 seconds of buffer, the audio data must be compressed; when it is read out of the buffer, it is uncompressed, but the lost data is not recovered. This is sort of like listening to MP3s -- they don't sound as good as the original CD.

Some CDPs get around this by using a smaller buffer (10 seconds). Some do both; for example, my Panasonic CT-570 lets you choose between a 40-second compressed buffer, a 10-second uncompressed buffer, or no anti-skip buffer at all (which works just like a non-portable CDP, in that the data is read directly from the CD for output).
 
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jlo mein

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good summary MacDEF.

I'm still in the dark about sony's g-protection though. I have no idea how much anti skip it has when its on setting "2". However, i think someone did say that when set to "1" it is a 10second uncompressed buffer.
 
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andrzejpw

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which model do you have? Some of the more recent ones, iirc, ONLY have compressed anti shock.
 
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purk

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Guys,
The older generations anti-shock system did not effect the sound quality in anyway. However, G-protection is a let down. Hopefully, someone can support me on this.

Purk
 
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kenchi1983

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and is this why some sony models (budget hip colors) sound muffed a bit...only a little. i did some comparing today.
 
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andrzejpw

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10-4 good buddy.


The newer sonys, in the ever prevalent to get 7 years of battery life out of 1 AA battery, have G-Prot turned on all the time. So its ALWAYS compressed.
 
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thomas

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The original g-protection also had G-proteciton running all the time, but it was a 12-second linear memory, no compresion

The cheaper Sony's probably use the smaller 4Mbit RAM chips, and as a result only have about 12 seconds compresssed memory. The expensive models have the 16Mbit ram, and can have either 12 seconds linear or 40 seconds compressed...

Antiskip time is only one factor, the rate that the CD player can read data and recover from skips is usually more important than the amount of memory it has. New players, such as Sony G-protection (10 seconds linear), have better antiskip than older players with 40 seconds compressed memory
 
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And let's not forget the first-generation 3- to 10-second ESP players: That antiskip TREMENDOUSLY compressed the 3 to 10 seconds of buffered sound, due to the fact that memory used for buffering was astronomically expensive in those days. So the PCDP manufacturers used very little memory (32KB or 64KB) in those players; in those days a player that used even 3 seconds of linear (non-compressed) anti-skip would have cost a would-be-buyer at least several hundred dollars (which would have been out of reach for most consumers).
 
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compressed g-protection is NOT always on on new sony models. I have the sony d-ej1000 and it has a switch for setting from "1" to "2". 1 is uncompressed and 2 is compressed. So you can turn it off if you choose to.
 
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Eagle,
Quote:

[size=small]And let's not forget the first-generation 3- to 10-second ESP players: That antiskip TREMENDOUSLY compressed the 3 to 10 seconds of buffered sound, due to the fact that memory used for buffering was astronomically expensive in those days. So the PCDP manufacturers used very little memory (32KB or 64KB) in those players; in those days a player that used even 3 seconds of linear (non-compressed) anti-skip would have cost a would-be-buyer at least several hundred dollars (which would have been out of reach for most consumers).[/size]


I have Sony D-515, it equips with only 3 seconds ESP. The sound quality is excellent.
My panasonic sl-s651c has a crappy 10 secs anti. The d-515 is the second most expensive discmans ever, while D-555 is the most.
 
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I don't think that the earliest ESP discmans compressed the data. The D-515, for instance, does not sound horrible like those awful 40-second ESP discmans that did compress. Also, I think the first generation G-protection discmans didn't compress either; the latter ones allow you to choose between compressed and uncompressed. The entire philosophy (gimmick) of G-protection is to focus on quicker laser recovery from shocks, not install ever increasing amounts of buffer (Sony went from 3 seconds to 5, 10, 20, and 40). It's the right approach, and works pretty well in my experience.
 
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Quote:

Originally posted by Kubernetes
I don't think that the earliest ESP discmans compressed the data. The D-515, for instance, does not sound horrible like those awful 40-second ESP discmans that did compress.


Well, it depends on the model. It also depends on the price point at which specific first-generation ESP models sold for; most of the low-end 3-second ESP models did compress the music, due to the fact that memory used for buffers were astronomically expensive (enough RAM for an uncompressed/linear 3-second anti-skip cost much more than many PCDPs) in those days.

Also, I would like to clarify the fact about G-Protection: The buffer is always about 10-12 seconds uncompressed. The G-Protection On/Off switch merely switches the fast laser recovery mechanism on or off.
 
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I think G-protection varies from model to model. My 915 has about 40 seconds of buffer and it has G-protection. My 725 has two modes - one lasts for 40 seconds and the other about 10 seconds. Turning G-Protection on usually makes the laser carriage move faster and the spindle to spin up when skips are encountered.

Please don't ask me again how I know how long the buffers last on my two pcdp.
 
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