Raspberry Pi I2S to SPDIF Hat

I agree. Describe your setup and your impressions. If you have any comparisons that's great. And make sure you do the test with the volumio 2.

Cheers,
Michael

 

Little worried about everyone testing on volumio2 (RC1) only, I know with the last moodeaudio TR's (test-releases) before 2.6 some of the kernel updates really messed with the sound. Think I'll use piCorePlayer to start & do the digi+ (with and without power supplies and my tweaks) comparisons first (using the PLL single clock). Might *try* to ask them (picoreplayer) about compiling in the patch... is there a PR in the official rasppi repo yet?

 

Maybe a public google doc's spreadsheet is in order.

 

Me too! I am going to start this test exactly as you described above.

 

Got mine today! Will be a few days before I can start testing it (waiting on a cable and some time to arrive). Thanks, again, Michael.

 

I'm super curious to hear the impressions of the sound.

 

It'll be cheap enough that it'll be worth trying for sure.

 

@Michael Kelly I know this is not the use case you wanted us to test but for me, the SPD02 is not recognized in my system as a Digi+. Strange because the 502 board you sent previously was. Right now I am just powering the SPD from the Pi (jumper left in). I guess there is no way to verify that the hat is getting power? Maybe that would be a good thing to include in production units, a small led?

EDIT: I just tried supplying 5v separately to the Pi and SPD (jumper removed) but my system still wont recognize the SPD as a Digi+. My software player (HQPlayer) does however see the Pi USB and HDMI outputs though so I know the Pi is on the network and being recognized. I am just not sure if the SPD is on. I have verified that the SPD is getting 5V from my power supply.

 

The goal is not to be cheap, but the perfect transport! The circuit is just very very simple, and great engineering by Michael on the power and computer (pi) decoupling, it takes a certain finesse. Maybe there will be a few hardware revisions to get it perfect... might be a giant killer, 'er or too expensive killer!

 

This is what I hope this will be. I hope it can rival my Soundaware D100 Pro. Or at least come close. Or am I dreaming?

 

If the other test dummies PM me their email address, I will create and share a google spreadsheet where we can list our feedback and issues.

 

The secret to Digi+ compatibility is the I2C address of the WM8804. Can you do a dump of I2C devices from your Pi? That may help see what is going on.

Cheers,
Michael

 

First cut of the HW reference manual is located here:

http://www.pi2design.com/uploads/4/8/5/3/48531975/503spd2_hw_ref_manual_p1_0.pdf

Updated data sheet is here:

http://www.pi2design.com/uploads/4/8/5/3/48531975/visio-503spd2_datasheet_p1.pdf

As always, feedback is greatly appreciated.

Cheers,
Michael

 

Some pics from the "test dummies" would be appreciated too!!!

 

Mike, I did the command lsmod | grep i2c_ to make sure the module is working. Here is the response:
i2c_bcm2708 4920 0
i2c_dev 5671 0

Then I ran the command sudo i2cdetect -y 1 to see if the SPD was detected and the table was blank.
When I install the 502 board, I see that is also no longer detected. I cant get the Digi+ board to show up anymore either. Now it seems the Pi3 doesnt see any of the boards. I went back and reimaged my SD card and still no luck. I am going to keep on troubleshooting but I wonder why now I cant see the Digi+ or 502 board which was working fine yesterday. I am going try the Volumio image and see if it will recognize any of the boards.

 

Hi Michael,

One of my first feedback is that coax BNC connection for audio is usually 75ohm, not 50ohm as used in many other industries for data transmission. Not sure if there is a 75ohm transformer out there and if this would be a better match for audio DACs. The BNC connector itself also needs to be impedance matched to 75ohm.

For AES/EBU, the standard impedance is 110ohm. I don't know how that would work out with the transformer impedance however.

 

https://www.flickr.com/photos/philipmorganphotography/albums/72157670653374266

 

50 ohm transformer run in balanced mode give 110 ohm impedance, so that should be correct. I did not realize however, that the BNC coax used 75 ohm. I did a quick google and verified you are correct. But, it's actually not too big an issue. I verified that the circuit I am using forms a 75 ohm impedance with the transformer and equalization capacitor. But, I do need to change the BNC connector to a 75 ohm version.

Thanks for the info!

Cheers,
Michael

 

Good idea, we could even get together for a Google Hangout. I usually do a hangout every Friday with my web dev guys, and find it really useful.

 

Is there any value to the RCA/BNC cables to connect regular coax to a bnc input, or are those strictly convenience? (That is, does it need to be BNC on both ends to ensure the impedance value?)