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 Post subject: My old Sony, MDP-455, LD player w/ AC3 Demodulator mod
PostPosted: 21 Jun 2020, 02:38 
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I was going through my old archives and found pics of my first AC-3 Demodulator mod installed in a player.

This was a Sony, MDP-455 that I had back in 2002 and it was my 2nd LD player I ever owned (my first is still my Pioneer, CLD-3030). The mod was only partially successful as I'll explain later in the post. For now, let's check out some pics (my apologies in advanced regarding my camera focus; I was just getting into photography and I borrowed a friend's camera that wasn't all that great).

A view of the player in question.....
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.... and a view of the underside (always liked Sony players in respect to seeing five isolating feet instead of the usual four on other brands)
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Here is the image of the underside w/ the AC3-RF board to the right....
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Regarding what I noted in this pic, the leads on the left power up and send the AC3-RF out signal to the AC3-RF Demodulator mounted on the top side. Also, per the instructions I received on this player about the lack of a mute control for the RF board, I still attempted to find one but failed in respect that anywhere I found a switching 5v point would adversely affect the player. Thus, as shown in the following pic, I ended up getting rid of the yellow wire and simply shorted the mute control per instruction.....
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Moving on, here is a view of the AC3-RF Demodulator in the player...
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.....and how the wires that were run through the plastic chassis....
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..... and on the way to the newly installed RCA jack.....
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So as I mentioned above, the mod wasn't totally successful and the key issue was the lack of a mute control on the RF board. The set-up did work and gave me awesome 5.1 audio but the big problem was that I would get an occasional loud squelch on my speakers just as playback was about to start. And of course, I found this very irritating as I did not want to be scared out my seat every time I started a movie (or started the next side change).

In any case, the player ended up having other issues as time went by and a shop I took it to stated that there was little they could do to remedy it (I think it was the spindle motor not getting up to speed or maybe the laser pick-up not reading the disc; can't remember). Regardless, since this was still the early 2000's, obtaining other players for dirt cheap made more sense instead of sinking more money into what was essentially an average player. The AC3 parts were removed before I tossed the player and they ended up in a Denon (RF board) and a ProScan (Demodulator board which was then removed again and currently not assigned to a new player yet).

All my subsequent AC3 Demodulator mods I have done since then have been perfect as all the other players have always had a good mute point for the RF board.

Hope everyone enjoyed seeing something different.
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 Post subject: Re: My old Sony, MDP-455, LD player w/ AC3 Demodulator mod
PostPosted: 18 Aug 2020, 02:42 
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Any chance you'd want to sell the demod board?
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 Post subject: Re: My old Sony, MDP-455, LD player w/ AC3 Demodulator mod
PostPosted: 18 Aug 2020, 05:03 
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Not really. But I suppose if for the right price, anything is possible. :?:

What would your plan be for it? Put it in a box or in a player?
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 Post subject: Re: My old Sony, MDP-455, LD player w/ AC3 Demodulator mod
PostPosted: 19 Aug 2020, 08:44 
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Most likely in my Marantz LV520 (D504 clone)... and either route the demodulated AC3 out the AC3-RF jack or hijack the VHF Mono Audio jack to keep it clean.

Right now I'm using a Rotel RDA-980 demodulator/decoder, but decoding and inputting to my AVR over the 5.1/7.1ch analog inputs means lose bass management and Audyssey room correction on my AVR. Stand-alone demods are priced well out of what I'm willing to spend, and the Rotel was an inexpensive option I found locally... at least until I can come across a deal Sony or Onkyo decoder that has passthrough or get really lucky and catch a Yamaha from someone that doesn't know what they have.

I wouldn't be able to spend an arm and a leg and understand if you don't want to let it go...
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 Post subject: Re: My old Sony, MDP-455, LD player w/ AC3 Demodulator mod
PostPosted: 20 Aug 2020, 06:41 
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I only have two of those boards leftover and for sure one of them is going into my CLD-D703. The other board is possibly going into a CLD-97 but I still haven't done enough research to see if it will fit inside of it.

Funny thing... when I first set out to add AC3 Demodulators in players, my intent was to do away w/ any extra box in between the player and AV Receiver. However, as I tried to implement it in the real world, I found the set-up to be a nuisance since I couldn't easily implement two digital inputs on my AVR in a "simple manner" to switch between PCM/DTS and AC3. Thus, I started to use these "2 in and 1 out" S/PDIF switchers that did clean up some of the inconvenience but now it brought back what I was trying to avoid which was to have another box between the player and AVR (not to mention I would have to manually flip a switch to change inputs on these boxes; they aren't auto or remote switching).

Anyway, as I started to really get back into LD two to three years ago, I realized w/ the number of players I had that I now wanted to implement dual players into every home theater set-up. However, now trying to use two sets of "2 in and 1 out" S/PDIF switchers for the two players looked even messier to me and equally inconvenient. In the end, I decided to buy up more AC3-RF Processors that had an S/PIDF output and simply use them as a convenient digital switcher for my two player set-up. Thus, I changed my implementation of the mods in which I was now keeping one player w/ the AC3-RF out and the other w/ the internal demodulator. Now with the system set-up like this, suddenly I had the most convenient way to remotely switch between different audio codecs from two LD players.

So the point I actually wanted to make is that if you can @ some point mod the Rotel processor w/ an S/PDIF output and turn your unit into a digital switcher / RF Demodulator (like a Pioneer, RFD-1), suddenly you would be able to let your Marantz AVR do all the decoding with its bass management settings and switch between AC3 and PCM/DTS with ease. And thus, the need for a separate RF Demodulator board now seems so unnecessary (unless you have two players in one set-up like I do and now there is a need for a second demodulator :roll: ).
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 Post subject: Re: My old Sony, MDP-455, LD player w/ AC3 Demodulator mod
PostPosted: 22 Aug 2020, 20:09 
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I have my eBay saved searches setup to pickup either a standalone demod or a processor that also has passthrough. The ideal would be a small demod (like the Yamaha) that could be tucked in the back of my rack and not take up space in the front. Still, I'm willing to spend too much since I have something working currently, so I'll bide my time for a deal to slip through.

My workaround for AC3 and PCM/DTS has simply been to setup two inputs on my AVR... one fed Video1 and Optical from my player, the other fed Video2 from the player and 5.1 analog from the Rotel... from there, I just have a single Harmony activity for laserdisc and a button programmed within that activity to toggle between the two inputs on the AVR (short-press for AC3, long-press for PCM/DTS). I need to add a third for Analog, but I only have one analog-only disc and it's also P&S, so I haven't been motivated enough to do so yet.
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 Post subject: Re: My old Sony, MDP-455, LD player w/ AC3 Demodulator mod
PostPosted: 22 Aug 2020, 22:27 
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shopkins82 wrote:
I have my eBay saved searches setup to pickup either a standalone demod or a processor that also has passthrough. The ideal would be a small demod (like the Yamaha) that could be tucked in the back of my rack and not take up space in the front. Still, I'm willing to spend too much since I have something working currently, so I'll bide my time for a deal to slip through.


It took some time for me to get a good deal on ebay for my last two processors but it was worth the wait (although my Sony, SDP-E800 is still driving me crazy trying to fix an issue on it :roll:). There is no rush so of course take your time to find something good.

shopkins82 wrote:
I need to add a third for Analog, but I only have one analog-only disc and it's also P&S, so I haven't been motivated enough to do so yet.


Not sure if this will work but I think you can get away plugging in the analog input to Video 1 or Video 2 and then utilize an "audio input selection" option on the Marantz (should have options like Auto, Digital, Analog, 6 Channel Ext). My two Denon AVR's has this feature and it works great in my system because I can automate it by simply turning off my Sony and Denon AC3 Processor to kill the digital signal which then tells the AVR to default back to analog.
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 Post subject: Re: My old Sony, MDP-455, LD player w/ AC3 Demodulator mod
PostPosted: 23 Aug 2020, 07:55 
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Probably worth a shot... if I get more than the one analog-only LD, I'll probably give it a go.
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