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 Post subject: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 13 Jun 2018, 13:14 
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I recently purchased a Marantz DP870 from eBay with the intent of using it to demodulate the AC-3 coming from my CLD-D406. However, to my dismay, I only realized after I placed the order that the only outputs are analog (decoded from the signal that comes off the demodulator chip, put in to 6 RCA jacks for surround or 2 for the L and R channels of that signal), while the receiver I have only accepts in analog stereo or Dolby Digital over coax.

As a temporary solution, I've placed an order for RCA to speaker wire adapters, so I can switch my speaker connections from my receiver to my DP870 when I listen to an AC-3 enabled disc. However, that's obviously pretty clunky. My ideal solution would probably be to purchase another receiver that accepts in analog surround, but I don't know if I could justify that at this time cost-wise. I did have a (pretty hacky) thought though: intercept the Dolby Digital sound coming off of the demodulator chip prior to the AC-3 decoding, and pipe it out one of the RC-5 jacks on the back, which I wouldn't use anyways.

This is kind of a long shot, but after looking at the schematic in the service manual for the Yamaha APD-1 (which uses the same chip that's in the DP870) it looks like it may be somewhat simple to take the signal, maybe throw it in to a breadboard with some off the shelf parts to mimic the APD-1's behavior, and repurpose one of the RC-5 jacks on the back (which at first I thought were outputting the Dolby Digital signal... oops) to output unadulterated Dolby Digital for my receiver to decode. Would anyone be able to provide some guidance with this, or am I barking up the wrong tree?

Also, if there's an easier solution to getting the analog 5.1 into my receiver (somehow) that'd be appreciated too. It's a Sony STR-K700 from an HTIB (yeah, I know. It was what I could find on Craigslist for relatively cheap). Like I said, it has analog stereo inputs, one optical input (already in use by my LD player for PCM and (eventually) DTS goodness), and one coaxial input. Obviously it supports Dolby Digital decoding, DTS decoding, and Dolby ProLogic (and PLII) dematrixing (is that the proper term?)

BTW: I tried uploading the APD-1 service manual, but it's apparently too large. You can find it here: http://www.owner-manuals.com/APD1-servi ... AMAHA.html. Schematic on pg 9. Also, the DP870 service manual can be found here: https://www.hifiengine.com/manual_libra ... p870.shtml (requires registration at hifiengine to download)

Thank you in advance for any solutions that'll let me enjoy the true power of AC-3 LD audio!
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 Post subject: Re: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 13 Jun 2018, 14:31 
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I had a Pioneer unit like that, but I had to run all 5 channels into the amp which had INs to then select that unit so I could bypass the internal of the 6.1 AV receiver I had.

As for what you have, I have no idea and hope someone else can help, but you may need a AV amp with more INs and OUTs in the back to do what I did.
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 Post subject: Re: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 13 Jun 2018, 14:37 
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Thanks rein-o, that is a solution I'm aware of and investigating to see if I could get such a receiver for cheap. Just wondering if I might be able to use my existing equipment with this somehow. Thanks though!
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 Post subject: Re: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 13 Jun 2018, 17:24 
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Ive never seen this unit but I’m %99.99 sure it could be modded for SPDIF or TOSLINK. I use a similar unit, ADP303 from Harman Kardon, and I know that can be modded because there is a thread here showing how to do it.

Affordable Receivers with multi-channel ins were a temporary thing. I don’t think any exist now on the market. I use an HK AVR235. If you find one of those be sure to get the real remote. It will run with a generic but it’s a PITA and finding an original is not easy.


Last edited by signofzeta on 13 Jun 2018, 18:58, edited 1 time in total.
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 Post subject: Re: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 13 Jun 2018, 17:53 
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Cool, thanks for the info signofzeta. Would you be able to link me to that thread? I couldn't find it in a preliminary search...

As for receivers, I found one locally with the necessary inputs, but like I said in a previous post it'd be nice to use my existing equipment. Plus it could make for a fun project ;)

Thanks again for the reply!
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 Post subject: Re: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 13 Jun 2018, 18:05 
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Funny that this question came up as I was spending the last three weeks or so researching the possibility. :idea:

I think (but I am not sure) that this could be the point where an S/PDIF interface can be tapped (somewhere right after the "data-o" pin on the LC8904Q chip)....


Image


However, I probably will never know anytime soon as I decided to not get a DP-870 since I just recently acquired a Denon, AVD-2000 that already has an S/PDIF output.

Also, if I was to go ahead and get the Marantz unit and mod it, I was planning on using this DIY board that I found on ebay.


Image


The seller provides some hints on the pin location for the digital output on some DSP chips (was able to confirm that I can use it on my Pioneer, CLD-M90 to obtain a digital output for it) but I was unable to 100% confirm the one used in the Marantz would have the exact pin that I needed (I'm basically guessing on the diagram above). I may continue researching it as it would be a challenge to see if it could be done.

Hopefully you can use the diagram I provided and continue the research to see if it can be confirmed. Let us know if you do find out anything.


Last edited by ldfan on 14 Jun 2018, 18:05, edited 2 times in total.
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 Post subject: Re: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 13 Jun 2018, 18:31 
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That's awesome ldfan! Could you provide a link to that board? Could come in real handy.

As far as where to tap the signal I was looking at the schematic for the Yamaha APD-1 (which has the same chip as the DP870) and it seems as though pin 65 "DAOUT" (digital output) right from the demodulator chip feeds the digital out ports (both optical and coaxial) on that device, along with pin 59 "MUTO" (muting output). You can see the schematic on page 9 of the APD-1 service manual, which can be downloaded from the link in my original post.
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 Post subject: Re: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 13 Jun 2018, 18:51 
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pianogamer5 wrote:
That's awesome ldfan! Could you provide a link to that board? Could come in real handy.


Here you go....

https://www.ebay.com/itm/132130972507

If you end up using this board, I would recommend using just the coax out as it’s tough using the optical if one has to drill out a square hole. Also, I was planning to remove the coax jack from the board so I could place the board anywhere in my player and then run a coax wire to the jack that I would mount.

In respect to the point you were referencing on the ADP-1, not sure that would work exactly the way you want on the Marantz since you want to intercept the signal at a point where the digital inputs switch (so you can use it as a digital input selector). The ADP-1 has no input switching option so that is why that is the only point indicated on the service manual.


Last edited by ldfan on 16 Jun 2018, 05:42, edited 4 times in total.
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 Post subject: Re: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 13 Jun 2018, 20:00 
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Thanks for the link and for the tips! What exactly do I need to hook that up? I see a plug for 5V and GND, and a screw on coax looking thing, not sure what exact cables/wires I'd need for that

Edit: found a power cable, but still confused on the DOBM screw on cable thing...
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 Post subject: Re: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 14 Jun 2018, 03:33 
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Harman Kardon ADP-303 Digital output

The ADP303 mod thread I mentioned earlier.
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 Post subject: Re: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 14 Jun 2018, 05:01 
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pianogamer5 wrote:
Thanks for the link and for the tips! What exactly do I need to hook that up? I see a plug for 5V and GND, and a screw on coax looking thing, not sure what exact cables/wires I'd need for that

Edit: found a power cable, but still confused on the DOBM screw on cable thing...



Here is a pic of the cable that is provided w/ the board....


Image


The middle pin will be soldered to the DOBM pin of the DSP chip in question (of course, if and when you identify the correct leg on the chip, don't solder directly to the chip itself but use a voltmeter to find an alternate pin that makes continuity to that leg). For the insulation section, I assume they want that soldered to a nearby GND point but I suppose you could just cut it off and and then surround the end w/ a shrink tube as it is done w/ the AC3-RF mod kits.

Here is a pic of what that would look like (the yellow side)....


Image


Last edited by ldfan on 14 Jun 2018, 05:05, edited 1 time in total.
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 Post subject: Re: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 14 Jun 2018, 05:04 
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signofzeta wrote:
Harman Kardon ADP-303 Digital output

The ADP303 mod thread I mentioned earlier.



Cool mod. Gives me even more confidence that a mod to the Marantz would be quite easy.

Now do I even want a 4th processor?? :lol:
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 Post subject: Re: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 14 Jun 2018, 14:31 
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ldfan wrote:
Here is a pic of the cable that is provided w/ the board....

I saw that pic, is it any different from a standard coax cable like this one?

For the moment I think I'm going to try a more hands on method like the one mentioned in the APD-303 thread signofzeta shared above, provided I can actually figure out what the exact solution is (the diagram mentioned is confusing to me...)

Thanks for all the tips!
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 Post subject: Re: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 14 Jun 2018, 17:36 
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pianogamer5 wrote:
I saw that pic, is it any different from a standard coax cable like this one?



That's a basic coax cable which means its diameter is too big to fit the terminal on the S/PDIF board.

The cable provided w/ the board is fine and is probably rated at 75ohm. I used them all the time in the AC3-RF mods I have done w/ no quality issues. Besides, you need something thin and low profile anyway when working these internal mods.


Last edited by ldfan on 14 Jun 2018, 21:22, edited 1 time in total.
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 Post subject: Re: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 14 Jun 2018, 18:06 
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ldfan wrote:
The cable provided w/ the board is fine and is probably rated at 75ohm. I used them all the time in the AC3-RF mods I have done w/ no quality issues. Besides, you need something thin and low profile anyway when working these internal mods.

Ooooooh, didn't even read that the cable was provided. Lol. Thanks! I'll update with how things go...
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 Post subject: Re: Intercepting Dolby Digital in a Marantz DP870 possible?
PostPosted: 18 Jun 2018, 07:04 
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pianogamer5 wrote:

As a temporary solution, I've placed an order for RCA to speaker wire adapters, so I can switch my speaker connections from my receiver to my DP870 when I listen to an AC-3 enabled disc. However, that's obviously pretty clunky.


I'm not sure I'm reading this right but are you going to try and have the DP-870 power your speakers "directly" from it?

If so, this is a "pre-amp" so it has no amplifiers to run speakers. At best, you might get a very low level sound in this fashion or possibly blow either the DP-870 or your speakers.
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