DigiOne RCA/BNC output for RPI

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cdsgames

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Joined 2015
To all this community that has been invaluable to me.

DigiOne specs :



RCA and BNC outputs (gold plated) only (absolutely no optical, it has by definition 4ns of jitter). No AES either its not a good medium for digital signals.
Noise level under 100uV ,we hope for 50uV, at the output.
Jitter target at BNC/RCA under 3ps on both outputs (we hope for 1ps).


That means no transformer for galvanic isolation , what we do is isolate the board at the input (after the wm8805) and then reclock with NDK Oscillators feed with own LDOs+ filters. (with meta-stability solved)


In total we use 10 LDOs on the board, 12 low pass filters, multiple buffers (with 0.07ps added jitter), digital isolator, common mode choke , isolated DC/DC convertor with filter on input and output.


We have a target price of 119 Eur...but its not set in stone.
Target release date April 30 (Sunday)...we will do our best but don't take it as a guarantee.
Basically what we think, its that DigiOne will be the best digital transporter on the market at ANY price (yes including those 5kEUR/USD transporters). Please correct me if I am wrong (if we hit those targets)


We are ready to listen to any feedback or questions . (no commercial questions will be allowed , we will create another thread for those)
 
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Dimdim

Member
Joined 2008
Looking at a similar to this one thread over at Volumio's forum, I noticed that you (or one of your colleagues) posted that this HAT would work with any generic I2S driver. That would mean that you're not running the WM8805 as master, but rather as slave. Which is the case?
 
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cdsgames

Member
Joined 2015
Gusser said:
Huh? SPDIF is essentially AES. AES3 is AES over 75ohm coax.

Not good enough? Do you realize how many standard AES interfaces that CD, DVD, or BluRay or streamed material has gone through before you play it?
Click to expand...

Big difference between then, one is balanced and other is not.

From my research both AES and RCA are considered poor choices for digital audio , BNC is the preferred .
 
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Gusser

Member
Joined 2014
cdsgames said:
Big difference between then, one is balanced and other is not.

From my research both AES and RCA are considered poor choices for digital audio , BNC is the preferred .
Click to expand...

AES is a prootocol, not an electrical interface standard by it's self. That's why you can have both XLR and BNC. The voltage levels are also different.

I agree that an RCA connector is not a good choice from a mechanical perspective. But electrically, there is no performance difference over a BNC.

If you look at standard transmission line theory, it's quite apparent that the physical distance of a BNC or RCA connector is much shorter than the wavelength at a 96khz sample rate, which is 6.14mhz.

The broadcast television industry used 50ohm BNC connectors throughout the analog NTSC era. Same reason, because at 6mhz, that mismtach is not relevant. Now when we went to digital video systems at 270mbs (143mhz), then the use of 75ohm BNC's became more widespread. When we went HDTV at 1.5 or 3gbs (745mhz / 1.5ghz) , 75ohm BNC connectors became mandatory. But not for lowly AES.

All this fuss over connector impedance for AES/SPDIF is just another audiophile ledgend. In the broadcast and mastering industry we don't worry about that because as electrical engineers working in the communications sector, we are required to understand transmission line theory. Provided the cable length restrictions, aka attenuation, are adhered to, there is absolutely no difference in audio performance between 110ohm AES and 75ohm BNC. We convert between them all the time with simple transformers. Many hundreds of them installed where I work at Technicolor's mastering facility..
 
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C

cdsgames

Member
Joined 2015
Gusser said:
AES is a prootocol, not an electrical interface standard by it's self. That's why you can have both XLR and BNC. The voltage levels are also different.

I agree that an RCA connector is not a good choice from a mechanical perspective. But electrically, there is no performance difference over a BNC.

If you look at standard transmission line theory, it's quite apparent that the physical distance of a BNC or RCA connector is much shorter than the wavelength at a 96khz sample rate, which is 6.14mhz.

The broadcast television industry used 50ohm BNC connectors throughout the analog NTSC era. Same reason, because at 6mhz, that mismtach is not relevant. Now when we went to digital video systems at 270mbs (143mhz), then the use of 75ohm BNC's became more widespread. When we went HDTV at 1.5 or 3gbs (745mhz / 1.5ghz) , 75ohm BNC connectors became mandatory. But not for lowly AES.

All this fuss over connector impedance for AES/SPDIF is just another audiophile ledgend. In the broadcast and mastering industry we don't worry about that because as electrical engineers working in the communications sector, we are required to understand transmission line theory. Provided the cable length restrictions, aka attenuation, are adhered to, there is absolutely no difference in audio performance between 110ohm AES and 75ohm BNC. We convert between them all the time with simple transformers. Many hundreds of them installed where I work at Technicolor's mastering facility..
Click to expand...

Good explanation .
 
Bas Horneman

Bas Horneman

Ex-Moderator
Joined 2002
basaudio.wordpress.com/
I took the liberty of putting the pic up here. pdf is nice but direct pic is better :)
 

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sckramer

sckramer

Member
Joined 2010
Nice! Do you plan on a shield over the clocks, looks like there's a solder pad for one?

Are you sending the clocks into the WM8805, or are you using it in PLL mode, then clocking somehow afterwards?

Is there a place avail to tap into MCLK?
 
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