How cheap RAM made portable CD players possible
This is a Sony Discman from 1992. It is a portable CD player to an extent that it can be moved from one place to another without carefully packaging it first.
Nowhere on the player it says that it is shock resistant. On contrary, the user’s instructions strongly suggest not to expose it to mechanical vibration or shock. Most often it would be used at home, connected to a 9V power adapter. Because it can also run off four AA dry cells, it probably can be taken to a picnic.
Sony does mention the possibility of using it in a car, for which Sony offered a springy mount arm and a mount plate to absorb bumps while driving.
This is a Sony Discman from 1997. It is slightly smaller, runs from just two AA dry cells but more importantly, it has 10 second electronic shock protection.
You can shake it, you can walk with the player bouncing in a backpack or you can carry it in this nifty shoulder bag, it continues playing. What happened in these five years? The answer: a precipitous fall in RAM prices.
More precisely, between 1995 and 1997 RAM price dropped tenfold, from around $30 per megabyte to about $3 per megabyte. Taking a slightly longer period, in 1998 the price of RAM was just one hundredth of 1990 level.
I am talking about dynamic RAM, the kind of memory that does not retain data when power is turned off. It is extremely fast and each memory location is directly addressable, so it is used to run programs and to temporarily hold data for processing.
Cheap memory allowed using dynamic RAM as a buffer in inexpensive portable CD players. Audio CD has data rate of about 1.5 Mbit/s, 10 seconds of CD audio take about 2 MB. In 1990 this would cost $200, in 1997 — just $6. When the player starts up, it needs several seconds of bump-free run to load 10 seconds worth of music into the buffer, then it reads and plays from the buffer, replenishing the buffer from disc. You can shake it and bump it, as long as it is able to find the track on the disc within 10 seconds, it is shock-proof.
Electronic shock protection made portable CD player truly wearable, walkable and even joggable. Here I have a Panasonic SL-SV553J model, “J” meaning designed for jogging. These days, you would not want to be seen carrying one, but twenty years ago it gave you the possibility to run and to listen to pristine digital audio without wow, flutter, pops and clicks.
Further models increased shock protection time to 20, 40, 200 seconds. Manufacturers used two approaches: a brute force one would be just increasing the RAM size. Another way is using lossy compression and storing compressed audio in the buffer.
This Panasonic CD player offers two skip-protection modes: one is 10 seconds, another is 40 seconds, and I am pretty sure that the second mode is when the player compresses Redbook audio into 320 Kbit/s MP3. When playing 128 Kbit/s MP3, the protection time is extended to 100 seconds.
But the same technological achievements that opened up a wearable market to CDs, brought portable CD players down. RAM prices continued to drop, the capacity of modules continued to increase, Flash Memory, which does not lose data when power is turned off, became commoditized. Nowadays flash memory is used in MP3 players, digital cameras and, of course, smartphones. Presently, $20 buys you 128 GB worth of flash memory, which can store about 180 CDs in full Redbook quality, this is unbelievable!
I did not have a portable CD player twenty years ago, I switched from a cassette Walkman straight to a solid-state MPMan F-60 MP3 player, the largest 128 MB card SmartMedia card available for it would fit about two hours of audio at 128 Kbit/s. They used to cost $50; they costs about the same now on eBay, just because they are not produced anymore.
With vinyl comeback and cassette comeback, I figured there got to be CD comeback, and I want to be prepared. So I got myself several portable CD players. I hope that they will not stop working all at once, so I’ll have a device to listen to my small CD collection, which I am too lazy to convert to FLAC files. ■
