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 Post subject: AC3 and right analog channel
PostPosted: 29 May 2021, 14:57 
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Hi,

I have a CLD-HF7G laserdisc player and I recently bought an AC3-Demodulator (Yamaha APD1). The demodulator works fine and I get the AC3 sound through an AV receiver. However, I'm a bit confused on the analog and digital tracks in AC3 laserdiscs. Since i didn't find anything that talks about this in the forum, I've decided to ask here.

Whenever I play an AC3 Laserdisc, the laserdisc player offers the digital channels and only the analog left channel. If I connect the demodulator to the av receiver, I get the AC3 soundtrack whichever channel I choose in the laserdisc player (digital stereo, digital right, digital left, analog stereo and analog left). If i choose analog right, the demodulator stops and there is no sound. This seems weird to me because I thought that the channel I had to choose for listening the AC3 soundtrack was the analog right and this is precicely the only channel that doesn't work when the demodulator is on.

So then I decided to play the Strange Days AC3 laserdisc (it has an audio commentary on the left analog channel). I connected the analog left cable to the TV, and at the same time I connected the demodulator to the av/receiver. Then I chose the analog left channel in the laserdisc player. Result: I get the audio commentary through the TV and the movie AC3 soundtrack through the AV receiver.

Well everything seems to work fine, but it seems this doesn't follow the general pattern of getting AC3 soundtrack through the right analog channel. Does anybody know why this is like this?
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 Post subject: Re: AC3 and right analog channel
PostPosted: 29 May 2021, 16:37 
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Read your post quickly, seems like it works fine for what AC-3 is.
You are dealing with a technology from the 70s that had to modify to modern standards of the late 90s and that's how they did it.
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 Post subject: Re: AC3 and right analog channel
PostPosted: 29 May 2021, 16:53 
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The fact that AC-3 takes up the space on the disc where the Analog Right usually resides is a trivia factoid. Knowing this is true only seems to confuse people. At no point does anyone ever in the history of LD actually select it that way.

If your player is an AC-3 player and the disc is an AC-3 disc then the AC-3 port will produce RF modulated Dolby Digital at all times, impossible to switch on or off, and the Analog Right will be impossible to select because what’s on it is garbage from an analog perspective.

If you have a pre-AC-3 deck you may be able to select Analog Right and will only produce ear splitting speaker destroying garbage.

Similarly, CD players made after CDROM was developed don’t usually play raw computer code through their DAC, the signal is instead muted.


Last edited by signofzeta on 29 May 2021, 17:21, edited 2 times in total.
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 Post subject: Re: AC3 and right analog channel
PostPosted: 29 May 2021, 16:55 
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Everything's working as expected in your setup. Just a little semantic confusion: the AC3 track resides on the right analog track, but that's not where you get it. Your player outputs AC3 whenever present over the AC3 coax output, except when you tell the player to output the right analog channel; it won't do both at once. In all other cases it outputs what you select through the player the normal way and AC3 to the demodulator at the same time. What I do is have a normal input on the AV for most LDs and another that I switch to for AC3.

Hope that clears it up!
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 Post subject: Re: AC3 and right analog channel
PostPosted: 29 May 2021, 17:19 
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rcarlson wrote:
Everything's working as expected in your setup. Just a little semantic confusion: the AC3 track resides on the right analog track, but that's not where you get it. Your player outputs AC3 whenever present over the AC3 coax output, except when you tell the player to output the right analog channel; it won't do both at once. In all other cases it outputs what you select through the player the normal way and AC3 to the demodulator at the same time. What I do is have a normal input on the AV for most LDs and another that I switch to for AC3.

Hope that clears it up!


This seems to add confusion. Like the OP, on my AC-3 decks I cannot select analog Right if the disc is AC-3. There is no either/or. I’m pretty sure this true to every machine, at least every Pioneer machine with factory AC-3. I suppose a modded CLD-97 would probably let you listing to the squeal...
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 Post subject: Re: AC3 and right analog channel
PostPosted: 29 May 2021, 17:24 
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So what you're saying is that the AC-3 signal is always output by the player, regardless of what audio track you've actually selected, except when you select analog right? Did I understand that correctly?

signofzeta wrote:
Similarly, CD players made after CDROM was developed don’t usually play raw computer code through their DAC, the signal is instead muted.

Man, that always confused me as a kid because I would always see the warnings on CDs with data on track 1 warning me not to play it - which of course I did because I was a kid - but I could never hear a thing. That explains everything!
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 Post subject: Re: AC3 and right analog channel
PostPosted: 29 May 2021, 17:29 
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glue69 wrote:
Since i didn't find anything that talks about this in the forum, I've decided to ask here.


Hello,

The help sections are on the main website, try:

https://www.lddb.com/help/ac3rf/
https://www.lddb.com/help/sound/

The Player will automatically output AC3RF to the dedicated port and MUTE Analog Right on the Analog outputs (that's why you can get Analog Left with the commentary).

Older/incompatible players might just output both analog sound tracks with a lot of noises on the right channel.

Looks like your setup works as expected.

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 Post subject: Re: AC3 and right analog channel
PostPosted: 29 May 2021, 17:45 
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admin wrote:
The Player will automatically output AC3RF to the dedicated port and MUTE Analog Right on the Analog outputs (that's why you can get Analog Left with the commentary).

Is this true with players with aftermarket mods as well? :think:
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 Post subject: Re: AC3 and right analog channel
PostPosted: 29 May 2021, 18:07 
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signofzeta wrote:
This seems to add confusion. Like the OP, on my AC-3 decks I cannot select analog Right if the disc is AC-3. There is no either/or. I’m pretty sure this true to every machine, at least every Pioneer machine with factory AC-3. I suppose a modded CLD-97 would probably let you listing to the squeal...

I have a CLD-79, and it behaves the way the OP describes: you can choose analog right, but if you do and it's AC3 you get nothing from either the demodulator or the RCA outputs (mute, not squeal). I went to triple-check this just now.
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 Post subject: Re: AC3 and right analog channel
PostPosted: 29 May 2021, 21:47 
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OK. It's pretty clear now. Thanks to everybody!
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 Post subject: Re: AC3 and right analog channel
PostPosted: 06 Jun 2021, 01:04 
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This thread educated me. Until now I had never tried changing the output channels while AC-3 was running. It’s true, if you actually select Analog Right it kills the AC-3 output on the player. I never knew this before...because there is no reason to ever try it, I guess. I had assumed the AC-3 was active all the time.
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 Post subject: Re: AC3 and right analog channel
PostPosted: 07 Jun 2021, 03:13 
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I think it probably depends on the player still.

Since most of my players are custom mods, one of my players actually kills the AC3 signal the moment I switch to analog. For my M90, I would have sworn nothing occurred to the AC3 signal when making any combination of changes to the audio selection but I'll need to double check that.

For factory AC3 players, it appears that is the case when choosing right analog. However, I think that is not always obvious since there is an extra bit of logic built into these players that shouldn't allow the right analog track to be chosen once the player knows it is an AC3 disc (unless maybe right analog was chosen before playback begins).
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