Hi everyone.
This is my 2nd post on diyaudio.com and hopefully I won’t sound like an idiot for what I am about to write (also, I hope I posted this inquiry in the correct forum since I know it doesn’t quite align with most of what you guys converse about).
I have been working on a project for the last three months to modify this Dolby Digital Processor from 1995 in such a way to add an S/PDIF output to serve as a means to obtain not only the demodulated AC3-RF signal but to also work as a digital switcher so that I can also utilize the optical and coaxial inputs to pass through DTS and PCM. (The processor currently only passes 6 channel analog which is a huge limitation if I want to integrate it into today’s modern gear.)
Anyway, long story short, I thought that I could utilize an I2S to S/PIDF converter board such as the one here to get a workable S/PDIF output…….
https://www.ebay.com/itm/386604200311?_skw=i2s+to+spdif&itmmeta=01JN5067X2PMW4F7DV7DA7M5KV&hash=item5a0367f177:g:uAIAAOSwsKdgAXll&itmprp=enc:AQAKAAAA4FkggFvd1GGDu0w3yXCmi1fALmE6yxdLqJDr+FxxmIRNN3BFoTKCIqMF8fPiOm1WLJbKW5FE3N9jFb55n5C+tmsmy4n/Xvjnq6KCWSLOzjSrg2f9Yt7o9PmfdFTYaPhvym4kfbue+7rfm5svLSvdT5DNyTtsqbWlsIg/LRtWAUbjpV6OuIahxvw3G1TCs7paS1KJJyaJ51KGCgjaauZPE7qODzHXWExpuieM9DwiCrXFW7TBkSmJWvat8J9GMj+pZK7fU/keVSqVGa0KqYzatRXn8UGKxygc8u81wdQlC8kC|tkp:BFBM4P6YoKll
My plan was to integrate this board with the DP-870’s Digital Audio Interface IC which is set-up like this within the processor……
…. And I went ahead and soldered wires that would intercept the following pins on the Sanyo, LC8904Q…..
So after much testing, I soon realized that I was going about it the wrong way. My belief (I’m sure someone can confirm this with me) is that my plan didn’t work because there is no I2S data on this Sanyo chip but instead it works in the EIAJ data format. I continued to study how the Zoran chip and the three Phlips D/A Converters interfaced w/ the Sanyo chip and hoping there might be some I2S conversion along the way. However, after reading some postings here about the utilization of the Philips TDA-1305T in CD players, it appears that EIAJ is definitely all that this processor runs on.
Moving on, I have thought about other options to make this work (as an FYI, there is no dedicated S/PDIF output pin on the Sanyo chip; first thing I looked for).
I could build an EIAJ to I2S converter board to make the Sanyo chip compatible w/ my I2S to S/PDIF board and I did notice that member “CM” has a schematic for it. However, as simple as it looks, it’s a lot work that will take some time for me to build and I would prefer something more off the shelf. Also, I’m not even sure it would work .
Another possibility I thought of was tapping pin 1 (DOUT/V) of the Sanyo chip but it is defined as an “EIAJ data and validity flag output”. I’ve searched on the web for a device that could read EIAJ and provide conversion to I2S or S/PDIF but nothing of the sort appears to exist.
So now…. I ask this community.
How do you think I should approach this mod or is this mod really just a pipe dream that wouldn’t even work? Any advice would be greatly appreciated.
This is my 2nd post on diyaudio.com and hopefully I won’t sound like an idiot for what I am about to write (also, I hope I posted this inquiry in the correct forum since I know it doesn’t quite align with most of what you guys converse about).
I have been working on a project for the last three months to modify this Dolby Digital Processor from 1995 in such a way to add an S/PDIF output to serve as a means to obtain not only the demodulated AC3-RF signal but to also work as a digital switcher so that I can also utilize the optical and coaxial inputs to pass through DTS and PCM. (The processor currently only passes 6 channel analog which is a huge limitation if I want to integrate it into today’s modern gear.)
Anyway, long story short, I thought that I could utilize an I2S to S/PIDF converter board such as the one here to get a workable S/PDIF output…….
https://www.ebay.com/itm/386604200311?_skw=i2s+to+spdif&itmmeta=01JN5067X2PMW4F7DV7DA7M5KV&hash=item5a0367f177:g:uAIAAOSwsKdgAXll&itmprp=enc:AQAKAAAA4FkggFvd1GGDu0w3yXCmi1fALmE6yxdLqJDr+FxxmIRNN3BFoTKCIqMF8fPiOm1WLJbKW5FE3N9jFb55n5C+tmsmy4n/Xvjnq6KCWSLOzjSrg2f9Yt7o9PmfdFTYaPhvym4kfbue+7rfm5svLSvdT5DNyTtsqbWlsIg/LRtWAUbjpV6OuIahxvw3G1TCs7paS1KJJyaJ51KGCgjaauZPE7qODzHXWExpuieM9DwiCrXFW7TBkSmJWvat8J9GMj+pZK7fU/keVSqVGa0KqYzatRXn8UGKxygc8u81wdQlC8kC|tkp:BFBM4P6YoKll
My plan was to integrate this board with the DP-870’s Digital Audio Interface IC which is set-up like this within the processor……
…. And I went ahead and soldered wires that would intercept the following pins on the Sanyo, LC8904Q…..
So after much testing, I soon realized that I was going about it the wrong way. My belief (I’m sure someone can confirm this with me) is that my plan didn’t work because there is no I2S data on this Sanyo chip but instead it works in the EIAJ data format. I continued to study how the Zoran chip and the three Phlips D/A Converters interfaced w/ the Sanyo chip and hoping there might be some I2S conversion along the way. However, after reading some postings here about the utilization of the Philips TDA-1305T in CD players, it appears that EIAJ is definitely all that this processor runs on.
Moving on, I have thought about other options to make this work (as an FYI, there is no dedicated S/PDIF output pin on the Sanyo chip; first thing I looked for).
I could build an EIAJ to I2S converter board to make the Sanyo chip compatible w/ my I2S to S/PDIF board and I did notice that member “CM” has a schematic for it. However, as simple as it looks, it’s a lot work that will take some time for me to build and I would prefer something more off the shelf. Also, I’m not even sure it would work .
Another possibility I thought of was tapping pin 1 (DOUT/V) of the Sanyo chip but it is defined as an “EIAJ data and validity flag output”. I’ve searched on the web for a device that could read EIAJ and provide conversion to I2S or S/PDIF but nothing of the sort appears to exist.
So now…. I ask this community.
How do you think I should approach this mod or is this mod really just a pipe dream that wouldn’t even work? Any advice would be greatly appreciated.
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The EIAJ spec referred to by the LC8904Q is CP1201 now CP340. This is the Japanese spec for SPDIF. The demodulated data is still compressed and requires any SPDIF transmitter to be setup for non-audio data. DOUT/V is the output used when the LC8904Q acts as a 4 to 1 selector and the data is not demodulated.
From the DP870 SM
TEST1, CLKS1 and CLKS2 are all connected ground.
Format selection for the TDA1305T
The TDA1305T dacs are setup to receive I2S data.
From the DP870 SM
TEST1, CLKS1 and CLKS2 are all connected ground.
Format selection for the TDA1305T
The TDA1305T dacs are setup to receive I2S data.
Thank you for the reply 👍🏻.
This gives me hope that I can utilize my I2S board after all.
I do have a question. I am using a board that utilizes the Wolfson, WM8805 and the specs seem to indicate that it automatically knows the difference between audio and non-audio data. Am I wrong to assume this and if so do you have an idea how to approach setting up this IC for non-audio?
This gives me hope that I can utilize my I2S board after all.
I do have a question. I am using a board that utilizes the Wolfson, WM8805 and the specs seem to indicate that it automatically knows the difference between audio and non-audio data. Am I wrong to assume this and if so do you have an idea how to approach setting up this IC for non-audio?
When the '8805 acts as a receiver it can the detect non audio data and set the appropriate flags. In your case it would be a transmitter so you would have to set all the flags and that may require a microcontroller.
I assume you mean as a "receiver" for the WM8805 that you mean an S/PDIF type input and not I2S (which is what I want to do)? If that is the case, that will be a complicated task for me to figure out 🙁.
I suppose there is no way to use that EIAJ data out (pin 1) of the LC8904Q as some way to interface data into the WM8805? I have thought about using this if it might work in conjunction w/ the WM8805.....
https://www.ebay.com/itm/3558854347...AwOEYHJsIxdPrKY+ffj9PxuYw=|tkp:Bk9SR8LRr-KVZQ
I suppose there is no way to use that EIAJ data out (pin 1) of the LC8904Q as some way to interface data into the WM8805? I have thought about using this if it might work in conjunction w/ the WM8805.....
https://www.ebay.com/itm/3558854347...AwOEYHJsIxdPrKY+ffj9PxuYw=|tkp:Bk9SR8LRr-KVZQ
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The WM8805 can be both receiver or transmitter depending on how it is configured. Assuming it is active pin 1, DOUT/V, outputs the selected input out of DIN1 to DIN4 and would require a SPDIF decoder to produce what is already present at DATAOUT.
So I just need to verify that pin 1 is sending digital data and not just a validity flag and maybe the board I mentioned w/ the CS8414 IC can decode EIAJ to I2S?
OK. Had some time to think about this.
The I2S data associated w/ TDA1305T probably won't help me much. The bit clock, master clock, and left/right clock do coincide w/ the Sanyo, Zoran, and all three D/A converters. However, the "data" at the D/A's do change since they are being split up for all the different channels (front left/right, surround left/right, and center/sub). I really feel that my only choice is tapping the data line between the Sanyo and Zoran chip to make this mod work.
Going back to the EIAJ data out, I'm pretty sure it has to accomodate both AC3 and PCM since the unit is designed for both. But regardless if it's just AC3, I'm assuming you are telling me that there is no device that can take that EIAJ output and convert it to I2S or even S/PDIF data?
The I2S data associated w/ TDA1305T probably won't help me much. The bit clock, master clock, and left/right clock do coincide w/ the Sanyo, Zoran, and all three D/A converters. However, the "data" at the D/A's do change since they are being split up for all the different channels (front left/right, surround left/right, and center/sub). I really feel that my only choice is tapping the data line between the Sanyo and Zoran chip to make this mod work.
Going back to the EIAJ data out, I'm pretty sure it has to accomodate both AC3 and PCM since the unit is designed for both. But regardless if it's just AC3, I'm assuming you are telling me that there is no device that can take that EIAJ output and convert it to I2S or even S/PDIF data?
Ok. I do admit EIAJ confuses me quite a bit.
Based on what I have researched, I “think” EIAJ in respect to just the data (nothing about the toslink standard) is similar to I2S in that it’s a means to convey digital data through various clocks and the one data line. However, the way it conveys the various clocks (and maybe data too) is different from I2S.
In respect to the single EIAJ output (pin 1) on the Sanyo chip, I assume it might be similar to a version of the standard S/PDIF with the clocks multiplexed into the signal (but I really have no idea).
My apologies for the being the newb that I am 🫤.
Based on what I have researched, I “think” EIAJ in respect to just the data (nothing about the toslink standard) is similar to I2S in that it’s a means to convey digital data through various clocks and the one data line. However, the way it conveys the various clocks (and maybe data too) is different from I2S.
In respect to the single EIAJ output (pin 1) on the Sanyo chip, I assume it might be similar to a version of the standard S/PDIF with the clocks multiplexed into the signal (but I really have no idea).
My apologies for the being the newb that I am 🫤.
EIAJ, in this case, is just SPDIF by another name. I2S is just one way of positioning the PCM data within a frame and arranging the data and clocks relative to each other. But there is no I2S or what the SPDIF spec refers to as valid audio data at the output of the LC8904Q. AC3 and DTS data is considered non audio data and that is what comes out of the LC8904Q. Assuming it is activated, you already have a switchable SPDIF output on pin 1 and on the schematic it is not connected. If it isn't activated, you will have to connect the clock, data and the relevant flags to a SPDIF transmitter.
Not sure whether it would help but here's something about encoded audio over S/PDIF. The validity and channel status flags are set to 1 when encoded bitstreams are transmitted.
The image posted above is the structure of a valid audio PCM frame. Non-PCM frames, which is what AC3 and DTS data is considered, is a very different animal.
First a correction. For non-audio data in my previous entries read non-PCM data.
AC3 and DTS data are encoded as long streams of data packed into audio frames, As the data can be read but not understood by an audio dac there are flags to tell the dac not to playback the data.
Below is the structure of a frame carrying non-PCM data.
First a correction. For non-audio data in my previous entries read non-PCM data.
AC3 and DTS data are encoded as long streams of data packed into audio frames, As the data can be read but not understood by an audio dac there are flags to tell the dac not to playback the data.
Below is the structure of a frame carrying non-PCM data.
The image in #13 is indeed for non-linear PCM data (AC3 / DTS) over S/PDIF and was obtained from Pg 10 of the relevant standard IEC 61937-1 (attached).
Cheers.
Cheers.
Thanks for clarifying what EIAJ actually is 👍
I did actually do some research with a group of people awhile back on lddb.com and it was confirmed that Pin 1 of the Sanyo chip was definitely inactive and the only way to turn it on would be through re-programming the CPU to allow it. Thus, I felt that was a dead end from the start and now I can officially stop going back to it as an option.
So that leaves me with my original idea of using the I2S to S/PDIF converter w/ the Wolfson WM8805. I probably have the right points tapped on the Sanyo chip but as you said the WM8805 can't be told to choose "non audio" data unless there is a way to input a flag to tell it that. I guess that is my next challenge which doesn't seem possible when I read how the WM8805 works (it automatically knows how to choose the non audio function if the input is S/PDIF but I want the input to be I2S).
Any suggestions if I am on the right track now? And if the WM8805 is not the way to do it, what S/PDIF transmitter option can you recommend?
No I2S from the LC8904Q. You will have to reconfigure your WM8805 board or find a board that can be reconfigured.