Hello-

I understand the basic reason for the RF outputs on laser disc players; there was not yet a standard for such signals when players and discs first had 5.1 soundtracks included. But, soon enough, there -was- a standard, and every DVD player had it included. Did any later players integrate Dolby Digital into their existing optical and/or coaxial digital outputs? That would have made things much easier than needing the rare add-on boxes.

With my limited knowledge of LD players, no.

The only way to get AC3 5.1 is via an AC3RF out.

DTS could be played back via the optical cables to to a receiver that decoded the signal.

Cheers,

I’m not 100% certain if this is correct, but I’m sure I read that this idea wasn’t popular with the manufacturers as adding an onboard RF decoder etc. would have pushed up the cost of what were already rather expensive players even further. If you really wanted to go the Dolby Digital 5.1 route, they did soon offer the option of AV amps with AC3 RF decoding included which also did away with the add on/stand alone box.

They intentionally left it out of the players because back then the license for Dolby Digital was more expensive. They don’t have to pay Dolby for a signal that isn’t usable Dolby so the player only outputs a section of the raw FR signal and has no Dolby logos on it. The license fee is applied to the de-modulator or receiver with the demod built in.

Cost was the biggest thing holding back LD for its entire left. Adding $11 to the BOM for a feature most users never even heard of didn’t sound good to them. Instead they put all that capability in outboard gear which meant that only people who wanted and could use 5.1 would be paying for it. It was a good solution for the time, very smart.

It's interesting, looking at the back of the Pioneer CLD-D515, this has, as you say, no Dolby logo next to the AC-3 out, just the text "AC-3 - RF OUT".

But the DVL-909 had the Dolby logo next to the text - "RF OUT (AC-3)(LD)" - presumably the player, incorporating a DVD section, had a Dolby licence anyway - it has a "Dolby Digital" logo on the front panel pertaining to that.

Which leaves the Denon LA-2300 as a bit of an oddity, as it proudly displays the logo on its front panel... I wonder if this was a mistake:



Actually I think I read somewhere here that some Hi-Vision players had internal RF-DD converters...?

Hi all-

Thank you for your thoughts and comments. If any players had got the baseband Dolby 5.1 digital output, the most likely ones should have been the DVD/laser disc combo players, since they already had all of the hardware included (except for the few parts needed to convert the Dolby RF stream to the exact format used in the DVD circuits).

My Pioneer CLD-D604 and CLD-D704, both first-year Dolby RF-output players, also have the Dolby logo on their front panels.

MSB did make an internal demodulator board but it required a separate output to be installed. I worked on a 97 years ago that had one. From what I heard it was a violation of the Dolby agreement with laserdisc and the option disappeared. I believe it had a coax output but I’m not 100% sure.

I’m pretty sure no player had a built in demod except maybe one of those private label joints.

It wasn’t an issue back in the day. It’s not like now, where basically everything with an optical input can decode Dolby Digital. Back then only real home theaters that cost at least $2000 could make any use of a 5.1 signal whatsoever so the demod was just another box for childless uncles to add to their pile of boxes that they already love. NOBODY was running around with an LD player trying to hook it up to something and failing because they didn’t have a demod. That person is a modern development.

After you got the demod you still needed a processor to turn the bitstream into six analog signals and an AVR than has six analog ins and also a subwoofer. It wasn’t all gamers and garage sales back then. Home theater was an expensive hobby.

The Yamaha AFD-1 RF demodulator is small enough that it should fit inside most LD players except a few tightly packed high end player.

-Remove the AFD-1 circuit board from its chassis to reduce its footprint. Screw it somewhere empty inside the LD player.
-Tap on the line side of the fuse on the primary AC side on the LD player’s power board to provide 120V AC to AFD-1.
-Cut the factory RF output signal lead and internally wire the RF signal to AFD-1 RF input.
-Wire the AFD-1 Coax output to the factory RF output signal lead which you cut on the previous step.
-You can probably keep the outside shield/ground leads intact as long as AFD-1 is grounded/mounted to the LD player’s chassis.
-This would turn the factory RF output socket into digital coax output.

This shouldn’t take more than a few minutes with the soldering iron on the 2 tap points, a couple of feet of high quality coaxial cable, and a couple of feet of 16AWG AC cords.

Now the question, what does this get you? Well, it frees up some cabling and a tiny bit of room in your equipment cabinet.

From my experience demodulators outlast players so that kind of work is a bit too clever to make any sense.

It definitely can be done and here once again is an example of one.....







This is the board that benedictus used to offer back in the day.

Looks like the MSB modification to me. Only drawback is that you have to use one cable digital cable for the digital out and a separate cable for the AC-3 out, this means it takes up two digital inputs on your processor.

If you get a separate demodulator that switches between the AC-3 RF and the digital then it only uses one input on your processor.

Yup…. That was a bit of the pain I had to deal with after I did the mod. To remedy it, I was using an S/PDIF splitter with a coax/optical input and coax/optical output that made it easier to deal with input switching but I wasn’t liking having to manually switch it all the time.

I decided now to just use my AC3-RF Processor that has one AC3-RF and four Digital inputs as a switcher for my dual player set-up. It’s now the ultimate twin player couch potato set-up for AC3, DTS, and PCM.

This is an interesting idea. I also thought about building my own demodulator; I am an RF guy, so I should know the basics of such an item. But, I looked at the internal board in the other pictures/posts, and that has way too many chips, some with -way- too many pins for me to want to duplicate its function. If it was just some AGC/limiting and FM/phase detection to baseband, maybe, but this is obviously way beyond that.

The “RF” in respect to AC3-RF is really just a descriptor that the signal coming out of the jack is RF based and not S/PDIF like standard optical and coaxial digital outs.

This is the only way Dolby Digital could work in LD since they decided to take away an analog audio channel to place this new data track on the disc (unlike DTS as they stole the entire PCM track on LD to make their codec work and also do it without any special decoding equipment like AC3-RF since it technically isn’t RF as the PCM track is already in an S/PDIF format).

Anyway, going to back to AC3-RF, the magic inside the Demodulator isn’t about RF but about QPSK (Quadrature Phase Shift Keying). Think of it like how in the early days of the internet we were able to carry a digital signal on an analog phone line. This is more or less the same concept of AC3-RF with a digital signal hidden in an analog one.

I remember bringing in my cld-1950 at the time to have the ac-3rf out added.
Left the player in the shop for some hours and went ld shopping elsewhere
Sure enough picking up the player you got robbed once again by paying for Clear and present danger and the much needed sony demodulator
That was a 600 euro day back then

And that sounds virtually identical to my experience back in the day too (around 1996/97?) only next door to you in the UK and with my original cld-2950. Crazy money really! That’s got me thinking now, how much were they asking for the Sony demodulator back then, as I don’t think the cost of that was too bad compared to that of the actual player mods and ac3 discs?

It was the day the first ac-3 ld reached Antwerp! Clear and present danger
People were waiting outside the shop to get their hands on it

The ac-3rf mod was about 200 euro in today’s money.
The sony mod-rf1 demodulator was about 185 euro
Clear and present danger most likely around 55 euro
… not to mention the much needed “decent high end” cabling that you “needed”

I have no regrets. It was great fun back in those days.
Getting a movie early while everyone was waiting for the vhs
Those were the days of collecting.
These days it’s all crap similar “collector’s” editions
If you also had one of those dts shopping bags afterwards… you sure were setup for life

I think you may have got in to the ac-3 capability just slightly before me then Kris assuming the discs arrived at a similar time in most of the Western Europe countries? I purchased my cld-2950 new in early 1996 totally unaware that the cld-d925 was due to be launched just a few weeks later - dealer never even mentioned this so was more than a little unhappy

Thanks for the price breakdown, you’ve obviously got a better memory than I! But yes, absolutely great fun back then, and sadly those hey days are now gone for good - today’s streaming/sound bar generation just don’t know what they missed

There were some hand built LD players with built in "AC-3 Demodulators" inside the players and they had it wired out to Digital Coax-Out or Optical-Out. I would have to pull out my Perfect Vision Magazines to tell you the Company that had them. It was at the Height of AC-3 "1994-1995". (Basically, a Auto-Demodulator built in).

MSB had 1 or 2 players with AC-3 Demodulator built in.(Very rare) Clone of the Panasonics LX-900u.

A Company named "Precision Laserdisc(Europe) produced and sold AC-3 Demodulator boards for a very short time.(Before I got into repairing Laserdisc players)

(So, basically use the coax digital or optical out to your receiver and it would be Digital Sound, DTS or Dolby Digital(AC-3) pretty nice!

These Demodulator boards were used for high-end rare LD
Players and high-end upgradable Sound processors and receivers.


I will post more details and photo's when I can locate my sources....

Hope this helps members
Ei
\../