I for one will be interested also if this works...please post if you have a go at this!

Will do, I have the board on order. No idea on when it will get here. Will update as soon as I can.

Am I correct in saying that currently we only know of one instance where someone (user Integra in 2013) has successfully added a Digital Output mod to a AC3RF Demodulator - which was a Harmon ADP303?

Reading back through the thread it does not seem clear how exactly user 'Integra' achieved it - assumptions are he tapped from a point connected to Pin 65 of Pioneer IC PD4606A...also not clear if user Integra used any additional components.

Just acquired a very cheap Marantz DP870 AC3RF Demod ...now I have two Demodulators
DP870 and the Yamaha DDP-1 ..both could do with such a solution.

Pin 65 was working for me on ADP-303 direct.

Thanks C++

Looking at the circuitry in SM's ( circuitry in both DP870 and ADP303 appear identical) Pin 65 on on Pioneer IC PD4606A is labelled (DAOUT) - Pin 65 is connected in circuit directly to IC LC8904Q QRO1 on Pin 44 (DIN1)

Been Asking myself what is the purpose of this connection between these two IC's .. ?? Given that a 'Digital Output' is not implemented..or in other words what is the purpose of feeding the Digital Signal into Chip LC8904Q.

Leads me to wonder atm with Tapping into this point what effect might be other than gaining a Digital Output...!?

A Denon AVD2000/Cambridge Audio V-500 Sound Processor comes with digital out...it would be nice to see it's circuitry to compare with DP870 & ADP303.. unfortunately Ive not been able to source a Service Manual/Circuit Breakdown of the Denon/Cambridge....as it might also use the same IC's.

LC8904Q is a switching IC to route the three digital inputs to the processor circuitry. If you tap the digital out of Pin 65 of PD4606A, this is only a link to the AC3-RF input (coax and optical input will not be usable w/ your new digital out). Thus, you do need to tap a digital out from LC8904Q if you want the same switching capability of a Denon AVD-2000. Unfortunately, it appears no one has been able to get a usable signal from this chip to make it happen.

Thanks ldfan - earlier in the thread user Integra made his own switching circuit.

The LC8904Q is selective through serial control to have pin 1 output the data on the inputs directly. Pin 35 is a demodulated format. You could use an i2s to spdif converter to derive the signal or figure some way to set the chip to output spdif on pin 1. I don't have a schematic for the DP870 to see what they're utilizing pin 1 for. It's possible they're using it for another purpose I will say that the Rotel units are super easy to modify with a digital out.

Thanks drewman !

looking at the SM's it appears pin 1 is not being utilised in circuit...see pic... C++ checked but could not see an output on Pin 1...so wonder how to manually set Pin 1 to output !

So are you hinting that the demodulated output on Pin35 is in i2s format..is that right?

The user Integra who managed to get this going did mention he could not get an output from the 'switching ic' so instead he created his own circuit to switch between RF and Digital Inputs to use the Digital Out.

With the Rotel unit you mentioned was it the RDA-980? just so happens I've sent to admin a copy of the RDA980 service manual today for the manuals section.

Cheers

I’ve been following with interest as I have a DP870 and looking to do the same.
I was waiting to hear how the “eBay” board went as the seller wont send to me in Australia.
I have looked over the schematics of both the DP870 and APD-1.
Pin 65 from the 4606 chip is definitely the way to go and should work otherwise I will be really surprised.

Couple of things to keep in mind.
1) the other 2 inputs of the DP870 are useless as they are an AC-3 format that didn’t happen (as far as I know AC-3 remained RF) these are unmodulated AC-3, I think the same as the APD-1 output..…
2) the DP870 is also an Encoder as well as Demodulator

So once the RF signal has been turned into a digital bitstream via the 4606 it is fed to the 8904 to be switched with the other 2 inputs (so now all 3 are the same bitstream format). So you can’t use the output from the 8904 as now the data has been manipulated to be decoded. The 8904 arranges and times the data steam to be finally decoded by the 8500 chip into its individual channels.

Anyway, I can’t wait to get my hands on one of these boards (or put something together myself) and try pin 65 of the 4606

Ref wrt ADP-303 & DP-870
Below Shows that a Digital Output from the DAI chip LC8904Q is possible on Pin1 (DOUT/V) but only if LC8904Q receives such an Instruction to do so from the devices Microcontroller...assume this instruction is not programmed, given C++ did not see any output when testing Pin1...makes sense also as Pin1 is not used in circuit. Seems there is no manual way to set pin1 to output.!?!

So lookslike if we want to use Optical/Coax inputs to use a Digital Output, we would then need an external switching circuit like Integra accomplished.

Lookslike 'us' in Australia can get that same Digital Board using Aliexpress - see link.

Small update on my progress with adding a digital out to the Yamaha DDP-1.

Yesterday, I received the digital out board and immediately went to work. I soldered the Coax input to pin 65 on the PD4606A and found +5V and GND on the pin out of the PD4606A as well. I accidentally bridged a couple pins because they. are. tiny. Bought some solder wick and flux today, fixed the bridge right up. My solder joints are not the best but I did verify I have +5V going to the power board .

I'm including pictures here and unfortunately cannot test AC-3 lock and digital output until I get home tonight.

https://imgur.com/hwcWKtf - Bottom of the board - Pin 65 digital out connection
https://imgur.com/F2LragH - Top of the board - +5V and GND

Will test tonight and get back to you all.

Another update and success! The Yamaha DDP-1 can be modded to output ac-3 sound over optical or coax. I swapped out my SDP-e800 and put the DDP-1 in its place. I waited to punch a hole in the back of the Yamaha until I knew this worked.

Good stuff! Thanks to everyone here for inspiring me.

Ask me any questions, I’m happy to help if I can.

Uploaded here => https://manuals.lddb.com/AC3RF_Demodulators/Rotel_RDA-980-EN_Service_Manual_Scan.pdf

Julien

Woohoo ! Big Congrats ldstl ! The first to use this Digital board and the first to achieve AC3 via Digital Output capability to a Yamaha DDP-1

Thankyou for posting the Pics...always really helps to see where things go.

I will be ordering a couple of boards now and I will have to see if I can find an easier spot to solder the +5V and Gnd to ..as I struggle to see those IC pins clearly these days

Looking forward to doing this mod!

I was going to mention this earlier when I saw the pic ldstl posted of the wires he soldered to the PD4606 chip. As an FYI, it's recommended to try and avoid soldering directly to tiny leg on an IC by simply seeing if you can first trace off of it w/ a voltmeter to find an alternate point that is easier to access. Here is an example when I soldered a wire to a DSP chip for my M90 mod.....





It’s understandable that some points will need to be directly soldered to a leg if it happens to go no where on the board. However, points like a 5v power point and GND can be found very easily w/ a voltmeter and in many areas far and away from any IC. Sometimes they are even labeled on a jumper or connector such as this image indicates.....



And if you can't find a label for a power point, you simply keep the device on and use your voltmeter to skim around the board to find it (I usually look on the connectors). For GND, it's even easier to find one by simply soldering a wire to the pad of the GND section of an RCA jack.

Anyway, I wanted to get this out there to save anyone grief if they end up damaging their IC and thus turning your Proccessor into junk.

Another Yamaha DDP-1 Digital Output Modification success!

Tested working nicely! - no more Lipsync issues when using DVD Recorder for Video enhancement.

That leaves the Marantz DP-870 to mod.