Raspberry Pi I2S to SPDIF Hat

Am I correct in surmising that the design is intended to isolate any noise coming from the Pi to below a reasonably audible level, so that using a standard USB power supply shouldn't significantly affect the sound quality? Not having to dick around with a fancy PSU would make this a lot more attractive to me.

 

Hey Michael. I can compare against my Diig+. Just let me know what you need.

BTW, would testing this against the Digi+ be a fair comparison? Did you mean compare this to a DAC+?

 

What kind of test do you have in mind? Repeating the RMAA measure with the 503dac1 vs the digi+ or just a listening test?

I might be saying a ton of BS, please correct me if I'm wrong.

The design of the speed1\2 using high quality LDO regulator is intended to reduce noise by a factor, not to isolate if you use a single power supply. The final noise level, being the reduction relative, is related to the noise of what you use in first place. The better PSU you use in this case the more the noise level will be lowered but the PI would still have a common GND to pass whatever shit it produces by processing.
To isolate the Pi power from speed1\2 (removing the jumper) you need two separate psu\rails.
What I'm trying to say is that its performance in theory SHOULD be crippled in a lesser way with a wallwart smps than other designs using inferior regulators, but why in the world wouldn't you want to use at least a linear psu?

 

Ok perhaps dumb question. What would happen if I supply the Pi and SPD with 5V (removing the jumper) but from the the same linear power supply? I was planning in simply buying a DC barrel splitter to connect to the single 5V output of my linear power supply. Would the Pi inject noise back into the power line which would then be sent to the SPD?

 

At some point (the splitter in your case) they will share the same 5v and gnd. Not much of change.
If I had to take a very wild guess, it could be even worse considering that the speed1\2 should implement a ground filter from the pi and you are bypassing it.
@Michael Kelly could certainly throw some light into this.

 

There is no ground filter. We do split the ground plane and join them right at the GPIO header wehre th 5V from the Pi goes. That way any noise in the Pi side tends to be reduced. Grounding is a black art and my experience is limited to the types of systems I've designed and tested. Some of which have had noise issues that required re-configuring what seemed to be a proper ground plane.

That's why you test and try new things. I would be inclined to think splitting the feed might help as it would tend to force Pi noise back to the supply without going through the hat. But, in the case of the SPD1 and SPD2, that noise would not likely create problems anyway. Still, trying it out seems pretty easy and low risk.

Cheers,
Michael

 

THe 503DAC1 is the equivalent of the DIGI+ AND the DAC+. Feel free to test it all, but mostly the digital side with coax to see how it performs compared to DIGI+. Listening test using whatever source material you are familiar with.

Right now I can only afford to send a couple of these as we have only just started building them. So I'll sign up Vastx and tboooe. Please email me, [email protected], with all your contact info so I can send them out to you.

Cheers,
Michael

 

I've been comparing the Digi+ more to my fully tweaked PC and believe I now have a good grasp of the characteristics of each. For my comparison, the only thing I changed was the renderer in my system. I connected the Pi3 and Digi+ via coaxial SPDIF to my Mutec 3+ reclocker. I had to use a BNC adapter on the Mutec end because it does not accpet coaxial. My PC was connected to the Mutec via a Light Harmonic Lightspeed split USB cable. Note that I am not sure if perhaps the different inputs on the Mutec had an impact on the differences I heard.

In comparison to each other I would say the Pi3 and Digi+ has a warmer sound with emphasis on the mids and mid bass. This resulted in vocals sounding meatier, with more weight. It actually reminded me of some tube gear I've had years ago. If I wasnt so lazy, I would probably still have tube gear. I like a warmer, more intimate sound. The music in general sounded less extended though. Notes felt more confined in a smaller area around my speakers.

My PC on the other hand sounded more extended with the soundstage seeming to envelope the room more. Notes seemed to extend physically farther and linger longer. Vocals were not nearly as warm.

The differences, aside from the mid and mid bass emphasis of the Pi and Digi+ were subtle, though once you hear them it is obvious. As with all things audio, what makes a system sound good versus great are the small things that add to the overall listening and visceral experience. I think to 99% of people the Pi3 and Digi+ will be spectacular renderer or audio streamer to a DAC, regardless of price. For this audiophool, it is worth spending the (much much) money to get the emotional connection to the music and the exhilaration I can get to hear a note seemingly linger in the air and wrap itself around me.

I am eagerly awaiting the SPD2 and hope it can match my PC. In fact, I really really want it to because my kids need a new PC and I would rather give them my music PC instead of having to buy another one!

 

Please take the reclocker out of the chain, thats a whole other set of connections, and a variable that might be messing with your results (good or bad) -- and not needed if we can get near perfect spdif in the first place!

 

Well the problem is my PC out is only USB so I need to have a converter in the chain.

 

Now that you mention the UP-Board. Your 503SPD1 DAC Hat board has REALLY caught my attention. I am dreaming of getting Roon Server running using this Pi2Media 503SPD1 DAC Hat & the UP board.

There is a Python library used on Raspberry Pi platforms to control GPIO pins.
https://up-community.org/UpWiki/index.php/RPi.GPIO

In addition to GPIO control, it is also used by many other libraries to query the Raspberry Pi hardware version as header pin layouts differed between certain versions.

"As the UP board has a similar header pin layout to the Raspberry Pi 2, we have created a port of the RPi.GPIO library for UP. This allows many existing Python scripts developed for Raspberry Pi to be used on UP also."

As the UP board has x86 CPU it should be able to be used with Roon Labs Server software. Without an x86 processor you can only run Roon Bridge.
https://roonlabs.com/downloads.html

The Up board appears to have the same form factor as the Rasberry Pi & the same 40 pin connector & pin definition GPIO header, and now with RPi.GPIO library for UP, maybe we might be closer to IS2 connected DAC with a reasonably fast CPU, RAM, storage etc...

I saw quite a few people in this thread talking about a 'cost no object' version, I would love to have aversion available like that that was compatible with the UP-Board.
http://www.up-board.org/

Carlos

 

Ok, please go direct with the pi/digi...

 

I think that Audiophonics did a good job on the case for the i-Sabre V3, would be great to have a power button option on the pi2design 503SPD1 to shut down the Ras Pi (gracefully)

Here is a link to the kit, which is reasonably priced.
http://www.audiophonics.fr/en/diy-d...yer-raspberry-pi-20-dac-sabre-v3-p-10384.html





The display & soft shutdown for the Rasberry Pi are a great idea, if you huys were thinking of adding more functionality, as well as improving the sound.

Hope you guys don't mind my suggestions, I am a little late to the thread. I am really looking forward to the 503SPD1

 

Carlos I like your thinking! This Up Board would be great run Roon or Minimserver and other software tweaks like Jplay, Audiophile Optimizer, etc. This little guy could easily replace my current Atom D525 PC that has a fan which I am not happy with. Plus this will take up less space and require less power. I wonder if this has enough horsepower to run Server R2?

 

Pi 2 Design, my company, already has a relationship with up-board. They are re-selling our 502SSD Storage Hat. The early versions of the up-board did not have the I2S bus enabled. Not sure why, but that's what they told us after we spent a few hours trying to get our 503DAC1 running. However, we are told the final rev will have it. As soon as we get one we'll test and all our hats will be tested on the up-board.

As for ROON we are currently working with them to add support for our 503HTA Hybrid Tube amp, and will add support for all our audio hats, including 503SPD1 and 2. Of great excitement to us regarding Roon is getting support in place for our up-coming 35W/channel Class-D Amp w/HP out hat. Not Audiophile level, but great for dorm rooms, game rooms, etc.

Cheers,
ichael

 

Hi Michael,

Great project!

I have PI2 and Pi3 and using HifiBerry DAC+ Pro. I use I2S ONLY

VERY IMPORTANT:

I did mod one of my DAC+Pro's with NDK NZ2520SD clocks, but that sounded a lot LESS open than XpressO TCXO's !!!!
Please use XpressO Ultra TCXO's, they are not that expensive.

I have my own wishlist, after testing and modifying a lot on DDC's I came to the conclusion that it is very important to:

1- Isolate ground completely from PI
2- Isolate 5V completely from PI - Include 5V header
3- Isolete 3.3V completely from PI - Include 3.3V header
4- Isolate TCXO's 3.3V completely - include 3.3-5V header for TCXO's
5- Include I2S header on PCB !!!
6- Put TCXO'x in DIL14 header for future purposes, possibility to exchange TCXO's is a MUST HAVE

Point 4 is also VERY important because this way you have ability to use 5V OCXO's if you plan to use them,
most of them need 5V, so if external power header for XO's exist, you can choose 3.3V or 5V.

Isolating power from XO's is very important, this gives a much bigger soundstage with a black background!

Hope you will consider my recommendations!


Cheers!

Alex

 

My listening experiences is quite similar to yours. I noticed a slightl bloom in the bass and softer treble than on the same via PC. I would be interested to test if the linear PSU would make a difference to that or is this about software? I am using the ipcoreplayer on the Pi and the foobar on Windows. Strangely though the Pi is easier to listen too though.

 

@Michael Kelly

Did you ever see Ian Canada's FIFO II project? FIFO II + Isolator board + DualXO II board?

I would wish you could design an rpi/up-board FIFO RECLOCKER-ISOLATOR-CLOCK GENERATOR

Maybe design 3 HAT's

1- FIFO RECLOCKER HAT which takes use of LRCB-BLCK-DATA I2S from rpi/up-board
2- ISOLATOR HAT which isolates I2S completely from FIFI RECLOCKER
3- DUALXO HAT which rebuilds clock signals with exchangeable clocks

All hats with their OWN, externally powered, psu's, or at least the possibility to do so.

See ian's twitter: https://twitter.com/iancanadatt/status/629460729733750784

Ian is designing DSD compliant FIFO right now, that will be another big leap.

Would you be interested to take that boat too?


Regards,

Alex

 

@Abartels
Man, you sure like to overdo things!
Please feel free to share something about you in the introduce yourlself thread and maybe write something there about the humongous psu in your avatar.
I'd like to know more

 

Alright! Now we are talking! Back to the audiophool/audiophile version I was talking about early on. I am in favor of keeping the design of the SPD boards the same but use higher quality components like clocks as mentioned by @Eugene du Toit. However. I have found in audio getting the best sound (highly subjective by the way) is less about having the absolute best technology but more about implementation, paying particular attention to noise, vibration, etc.

I do admit my nerdy side loves the Fifo projects referenced by @Abartels . Lots of possibilities here to improve on the sound. Gotta remember its only been a few weeks since this project actually started!

I've been thinking more about the UP Board and I think it could be a great solution for my server. I would run Windows 10 and Minimserver on this device plus OS optimizations Audiophile Optimizer, Fidelizer, and maybe Jplay. I would use a second UP as my renderer using the same OS and optimizations and of course a SPD hat. Or I could use my Pi3 with SPdlD hat, whichever gave the best sound. This setup would essentially mimic my current setup but at much lower cost and power consumption. Not to mention I could save a lot of space in my rack. Hmmmm...I am really liking the possibilities.