Modifiying CD player to accept external I2S signal

[Sandm0n]

Hello,


I have a Rotel RCD-971 CD player that I would like to modify so it can accept I2S signal from an external digital inputs receiver switch that has a I2S output.
In this way I will be able to connect external digital sources and use the Rotel's PCM63 DAC chip and have the anlalog output from the Rotel's analog outputs.
I need your help to understand where should I connect the DATA, BCK, LRCK, MCK outputs from my digital input selector to the PMD100 in the Rotel.


I'll appreciate any suggestions.


Thanks

 

[Sandm0n]

PCM63 and PMD100 marked

 

[lcsaszar]

Hello,

It seems like DIN is Digital In (DATA - pin 1), BCKI is Bit Clock In (BCK - pin 2), LRCI is L/R Clock In (LRCK - pin 28). MCK is not needed but you can connect to XTI (pin 6). Of course, disconnect the internal sources of these signals, by using a mechanical or electronic switch.

 

[Sandm0n]

disconnect the internal sources of these signals, by using a mechanical or electronic switch.

Thank you.
I will use I2S switch so I could still use the CD player as intended.

 

[Sandm0n]

Hello,

It seems like DIN is Digital In (DATA - pin 1), BCKI is Bit Clock In (BCK - pin 2), LRCI is L/R Clock In (LRCK - pin 28).

Should I connect it before or after the resistors? do I need to include them?

 

[lcsaszar]

Should I connect it before or after the resistors? do I need to include them?

Include the resistors.

 

[Sandm0n]

Thanks

 

[rfbrw]

MCK is not needed

Are you sure about that ?

 

[abraxalito]

PMD100 has an MCLK input (pin6) - do you think that the DAC and filter section can run correctly when MCLK (generated by an XTAL inside the player) isn't synchronized to BCK and WS from your external source?

The PMD100 DS says this :

The PMD-100 is designed as a synchronous circuit, which means that it uses a master clock input XTI which is always synchronized with and typically derived from the input data stream.

 

[Sandm0n]

PMD100 has an MCLK input (pin6)

From the schematics It looks that the PMD100 pin 6 is connected to both U631 pin 8 and U611 pin 9

 

[rfbrw]

U631 handles distribution and buffering. U611 reclocks WCKO/LE.

 

[Sandm0n]

U631 handles distribution and buffering. U611 reclocks WCKO/LE.

Should I use the marked point as a MCK input?

 

[abraxalito]

I'd break the track feeding pin9 U631 and apply MCK to pin9 with a 10k pull down to 0V.

 

[Sandm0n]

I'd break the track feeding pin9 U631 and apply MCK to pin9 with a 10k pull down to 0V.

Do you mean connecting the MCK to pin 9 and a 10K resisttor to ground?

 

[abraxalito]

Yes, that's the idea. You want MCK to have a defined level if its not connected to the external source - hence the 10k.

 

[TNT]

Beware... i2s is not a longhaul interface. It is ment for short (centimeters) tracks on a circuit board.

//

 

[Sandm0n]

I know that I2S signal should be as short as possible but have a look at the pcb and the location of the Data, BCK, and LRCK and how "far" they are from the PMD100.

 

[Sandm0n]

Yes, that's the idea. You want MCK to have a defined level if its not connected to the external source - hence the 10k.

But I do plan to connect the MCK from the external source, so should I still need to cut the trace and connect the MCK from the external source to U631 pin 9 and pin 9 to GND using 10K resistor?
or maybe I got it all wrong

 

[abraxalito]

You need to cut the trace for sure. I was assuming you'd arrange a 5pin connector for the I2S signals and might wish to disconnect your source from the player at some point. If that's never going to happen then the 10k can be omitted.

 

[Sandm0n]

You need to cut the trace for sure. I was assuming you'd arrange a 5pin connector for the I2S signals and might wish to disconnect your source from the player at some point. If that's never going to happen then the 10k can be omitted.

My plan is to modify the CD player and connect this digital input reciever to the CD player so I can connect and switch between different inputs and still use the CD player as intended, this digital input receiver/switch has I2S, Toslink, Coaxial and AES inputs and I2S output.
What do you think will be the best way to integrate this receiver wih the CD player?


Thanks