Raspberry Pi I2S to SPDIF Hat

If you read what Michael did he created that product and Incorporated a quality DAC also. One board serving more than one application.

 

We decided to cancel the SPD1 and roll its functionality into an updated version of our DAC board. It was simply more economical that way.

Cheers,
Michael

 

I must have missed that announcement. Anyway... since I was impressed by the price\performance ratio of your dac, I imagine that an updated and improved version with separate power from Pi, tranny coupled rca spdif output and double clock should be very nice

 

I am no expert but I believe BNC is the only way to get true 75ohm. Check out this link for more info:

http://www.bluejeanscable.com/articles/75ohmrca.htm

 

I got the SPD in my system and verifies that it works. I am letting it burn in for a few hours before I start listening.

 

Makes sense from manufacturing point of view.

 

Obviously the cable and connectors must also be a true 75 ohm till end point. If you do not have BNC then it has to be "converted". What happens then?

 

Had the chance to listen to the SPD for a while in my system last night. The Volumio imaged provided worked perfectly so playing music was literally as easy as plugging the Pi in and connecting it to my network. For my initial test I used the SPD and Volumio as a renderer receiving music from Minimserver. This is not my main source playback chain where all of "audiophile" gear is. The reason why I cannot use my main system is that I am using HQPlayer software which requires a special network audio adapter (NAA) program running on the pi. Since the SPD patch is not yet availabe I cannot use the NAA. I know I can use a standard Digi+ image but I want to test the new clocks. I may do this anyway as more of a direct comparison to the Digi+.

I first tested playing tracks with different formats from 16/44.1 to 24/192 and everything in between. The SPD worked as expected. It would be cool to have some sort of indicator which clock was being used. I think if the additional clocks will be advertised as an improvement over the Digi+ I think people would like to see maybe a little LED. I know an LED wont have any performance value but I thnk bringing additional attention to a differentiating feature is a good thing (yes I am in marketing).

Anyway, on to my impressions. Just listening to the SPD powered through the Pi with my linear power supply, my initial impression is that the SPD sounds very clear, open and airy. Since the Volumio image does not yet work with the Digi+ I cannot easily do a comparsion but from memory, I will say that the SPD definitely does not have that over bloated sound the Digi+ has. I listen to mainly acoustic and vocal jazz so I tend to focus mainly on the midrange which sounds very neutral with the SPD. So far, the strength of the SPD is in the highs. Notes seem to rise and float in my room. Guitars strings sound crisp. Overall, listening to the SPD is very enjoyable. I would like to do head to head comparison against the Digi+ so I can identify more differences but so far it seems the SPD does indeed sound better. I will continue to listen to the SPD then switch to powering it and the Pi separately to see if there are any improvements.

@Michael Kelly 2 questions:
1. when will the patch be ready?
2. will there be a Volumio image that also works with the Digi+?

Based on my initial impressions I would say that Michael and team have achieved what they wanted in making something that sounds better than the Digi+. How much better it is than the Digi+ remains to be seen. I will report back as I listen more.

 

Then it depends on the cable implementation. Perhaps ask the cable manufacturer? If it is not 75ohm than converting to BNC wont make it 75ohm. But how much of a difference does it make??? I have no idea.

 

I got to spend some time doing critical listening yesterday, so I'll add my first report on the 503SPD2 connected to a Pi2, both running off a plain jane switching power supply (I'll try a battery -> LM317 supply later). I used the SPD2 to feed my Gungnir Multibit via a Blue Jeans Audio BNC to BNC cable.

I don't have any way to compare the SPD2 against another SPDIF source because I sent my Digi+ to @Hands to get his take on it.

Comparing against using USB into my Gungnir Multibit (a direct head-to-head comparo) and against my memory of the Transient USB -> SPDIF converter, I'd say the SPD2 is clearly better than USB and probably a peer to the Transient. Some differences between the Transient (a $700 product) would probably be evident in direct comparison, but I don't have it here for direct comparison.

The SPD2 does that "SPDIF thing" where it expands the soundstage significantly which is, for me, reason enough to use it. It's not just that the soundstage gets pushed further out, which I like. It's that the placement of instruments moves away from a "3-blob" placement and becomes more like musicians on a stage. My go-to track for soundstage comparisons is Beirut's "The Rip Tide" if anyone wants to try to corroborate this.

The patched version of Volumio worked as expected, which is to say it worked fine except for being unable to catalog the contents of a large 150GB shared folder on my Mac. A smaller (65GB) shared folder posed no problem. This is not a SPD2 problem, this is a Volumio problem and one that could probably be resolved with the right command line hacking.

I briefly futzed around with feeding my Leckerton UHA-6S.MKII via SPDIF, and that worked fine too, though I didn't do any critical listening to that setup.

I'm looking forward to trying the SPD2 with a linear power supply. Other than that, not much to report. Plug it in, and it works (with the hacked Volumio image), and it sounds great!

I'm interested in getting Rune Audio running with the SPD2 because Rune doesn't have the issue with shared folders that Volumio RC1 does, though Rune is not quite as nice a UX as Volumio.

 

@Michael Kelly

Did you find a good 75Ohm BNC replacement? I used an Amphenol RF on the digi+

Would like to get the part ordered for the D2 testing, Thanks!

 

Sorry, I lost track of this issue. I will look at the options tomorrow for a part that will fit into the same footprint. I am pretty sure the vendor had both 50 and 75 ohm versions.

Cheers,
Michael

 

Well, I feel like an idiot! The connector on the SPD2 is already 50 ohm! I simply forgot what I had ordered. I had my production guy check it for me and we are using Tyco part# 1-1478032-0. Sorry this created so much angst!

Cheers,
Michael

 

You mean already 75 ohms?

 

Woops, I think you meant to say that the connector is already 75 ohms (I looked up the part number)

 

Well knowing this now the SPD magically sounds better! LOL! Expectation bias anyone????

 

There seem to be few bounds to my idiocy today! Thanks guys!

Cheers,
Micahel [edit] <-- Apparently I can't spell my own name! Would you buy a board from this guy???

 

I noticed you can order 75ohm cables, both connectors 75ohm bnc to rca, so basically you can use all analog spdif connectors from dac. Like rca, bnc and xlr.

I did not notice, but what are SPD2 power requirements and what is XLR connector ohm? 110?

Will it send same signal same time over XLR and BNC?

 

XLR is 110 ohms differential (aka balanced). The signal is the same as BNC, just differential.

Power has not been measured, but should be under 200ma @ 5V.

Cheers,
Michael

 

@Michael Kelly : does spd2 work with other board like odroid c2, assuming that c2 use volumio?