So you got yourself a recent LD player with an AC3RF output or you are planning to get one?

You might be wondering what is needed to process it correctly... or more simply what could be different from the AC3/Dolby Digital soundtracks found on DVDs?

 Just a few basic checks:

• LD Players able to ouput AC3RF information have a dedicated coax output at their back (most of the post 1995 models should be able to do that properly, PAL players have to be recent and be able to play both PAL and NTSC)
• To identify laserdiscs with AC3 soundtrack look for the logo at the back (sometimes a sticker on front for US releases or Obi information for Japanese releases). The logo changed over time:
• "AC3RF" (early releases only)
• "Dolby Surround - AC3 Digital" (randomly)
  
• (most common)
  
• On very late releases featuring Dolby 6.1 encoding the "SURROUND EX" logo appeared (in Japanese サラウンドEX)
  

LD Dolby Digital soundtracks are more compressed than most DVDs (384Kbps instead of 448kbps).

So... you might rightfully ask "Will LD soundtrack sound weaker, less defined than their DVD counterpart?" Normally they should but the fact is that they don't sound weaker, they actually often tend to sound better, especially compared with DVDs released more than 5 years ago. How is that possible? The audio mastering was made for a purely 5.1 system (full 5 speakers + dedicated subwoofer). If you had only a surround of stereo system, then the Digital Tracks (standard Dolby Surround) were available. In the meantime, DVD had only one AC3 soundtrack that was supposed to sound as good as possible on any system, from a simple stereo TV set to a full-blown THX speakers set. Compromises were made on dynamics and frequency ranges to make sure your Death Star final explosion in Star Wars does not make "plop" on your speakers.

All in all, there are potentially better AC3 soundtracks on LD.

LD Dolby Digital soundtracks are actually stored in an analog format.

They are physically stored on the right left analog track of NTSC LDs. They are digital information stored with modulation -- just like you used to access internet (digital) over your phone line (analog) a few years ago via MOdulation/DEModulation (MODEM).

The analogy (pun intended) still works for LDs because to enjoy their AC3 soundtrack you will need a demodulator able to transform this analog signal into a digital bitstream that your A/V amp can use.

Three possibilities:

1. You own a high-end A/V system and it provides a built-in AC3RF IN connection
2. You own a rather old (up to early 2000's) A/V system also with this built-in AC3RF IN connection
3. If not 1. or 2. then you must purchase an additional piece of equipment called an "AC3RF Demodulator"

For a rather extensive list of equipments able to process AC3RF directly, please consult:


AC3RF Demodulators

They were sold in Japan (100V), USA (110V) and Europe (230V) during a few years and can still be found on eBay or elsewhere from time to time from these makers:

• Pioneer (mostly Japan and USA) - RFD-1
  
• Kenwood (Japan, USA, Europe) - DEM-999 series
  
• Meridian (USA) - Model 519
  
• Lexicon (USA) - LDD-1 (the only one I found wouldn't lock on RF signal at all, haven't tested a working unit)
  
• Yahama (Japan, USA) - APD series
  

Other manufacturers were simply OEM version of Pioneer or Yamaha designs.

Basic demodulators such as the Yamaha will simply take the AC3RF in and demodulate it to AC3 OUT while switching on the DEMODULATE led when an AC3RF signal is detected.

Examples:


Other gears are a little more elaborated and will accept both digital signal (toslink/coax) as well as AC3RF in and will either "pass-through" the digital information or automatically switch to AC3 demodulation is the signal is detected. This way, in case you own a dual LD/DVD player, only 2 connections from the player to the demodulator will provide a single output to your A/V amp. Very convenient to avoid creating 2 different profiles or switching cables manually when you swtich from between LD and DVD.


One last word on Dolby Surround EX 6.1

Because the technical specifications of Dolby Surround EX were not finalized when the first few EX LDs were released, your A/V Amp will not detect a 6.1 soundtrack but only 5.1. This is normal because the information flag that tells your system it actually is a Surround EX encoded soundtrack is missing. You will have to manually force the 6.1 mode to take full advantage of it.

The complete list of Surround EX LD titles is:

1. Austin Powers: The Spy Who Shagged Me (1999)  LBX/AC3    1999-11-16    NTSC    USA
2. Bone Collector, The (1999)  LBX/AC3    2000-03-14    NTSC    USA
3. End of Days (1999)  LBX/AC3/Uncut    2000-04-18    NTSC    USA
4. Fight Club (1999)   LBX/AC3    2000-05-26    NTSC    Japan
5. Haunting, The (1999)   LBX/AC3    1999-12-28    NTSC    USA
6. Haunting, The (1999)   LBX/AC3    2000-04-25    NTSC    Japan
7. Star Wars: The Phantom Menace (1999)   LBX/AC3/THX    2000-04-07    NTSC    Japan
8. World is not Enough, The (1999)   LBX/AC3    2000-08-04    NTSC    Japan

Conclusion

I hope you know a little bit more about AC3/Dolby Digital on LDs now. If you still have questions, please do not hesitate to send me a message through eBay.

Julien
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http://www.lddb.com/ - The LaserDisc Database