Raspberry Pi I2S to SPDIF Hat

Just wondering if you got the second batch out, I haven't seen it so just asking to make sure it didn't get lost somewhere?

 

Vastx!

Have you tried to run it from different PSU's? Combinations like RPI from stock PSU and Hat from special PSU or just run RPI from stock and see how
it is different from modified PSU.

I am just wondering what type of PSU is best to build for it, since i do not have hat and i can't do testing myself here. It would be great help from your side.

 

Ok, for the sake of science I'll give it a try with the worst I've got and see how much it is really insensitive to a shitty psu

 

It has not gone out. We've been short staffed this month and it is taking longer to get my pet project done! Actual paying work (ugh) is taking priority. But, I am meeting with my production manger this morning and it is on the agenda. The units have been built, I just need to get them tested and shipped.

Cheers,
Michael

 

OK... no need to listen... just powering them on told me the difference.
Previously I stated that the shitty smps bundled with the Pi2 made an horrible noise. I plugged it in the Pi with the speed2 (jumper on) and it was dead silent. So I thought some condition may have changed, better to check the digi+ again. I plugged the smps into the Pi with the digi+... the freaking noise was back
The only hardware difference is the speed2 and the digi+ (one runs volumio and the other moodeaudio, but it's irrelevant to the point).
No comments yet about the sound quality difference with the speed 2 and different PSUs but I have to give @Michael Kelly that he knows what he's doing.
I'm afraid to find out that he made my 60 bucks psu a lot less useful regarding sound quality

 

This will show my total ignorance, but would the SPDIF HAT sit on top of the mSATA SS shield if you were stacking the boards to make a media player. This looks like a very cool solution to having a small media player /server as part of my audio set up. I currently use a discarded e-book with FB2K and the android app to remotely control the media library over wifi..dB

 

I made some tests on the matter of PSU and Speed2 and sound quality. Well... long story short the speed2 is quite insensitive to psu changes.

With the digi+ I was able to perceive an improvement every step of the way, from the noisy smps to a good smps to a 10usd lm317 to battery to the LT3042 double rail PSU. The difference ranged from unlistenable to very good.
With the speed2 the noisy smps gives already a very good performance. There is not much difference with a good PSU. The only things I was sure were different were a little more air in the highs and a wider soundstage, but overall not a great difference. If I had to say a number to express a gap I'd say a 4\5% difference.

The speed2 made my psu a lot less useful than it was with the digi+ to improve the sound quality. If you're gonna use the speed2 and need to buy a PSU don't spend big money... otherwise don't expect huge difference.
In the end a 35usd Pi2 and a 50usd speed2 with a 2A phone charger smps and a micro sd card make a very nice streamer for under 100 usd. Unbelievable. It is what I spent for the transformer and the PSU Had I known...

Tomorrow I'll be testing the sped2 vs a teac vrds cdp as a transport. It's been a while since I listened to it at home.

 

Lovely afternoon today as a friend came by with his Teac VRDS 25 to compare it to the raspberry.
The test involved several songs played through the cdp as a transport with a cd burned from the file that were being feed to the raspberry.
Raspberry and speed2 were at their best shape... double clock firmware and double linear 5V.

Despite my expectation... well... I would lie if I said there has been a fight. The CDP really shined with no fear to be obscured by the Pi\speed combo. Costwise of course there was no fight too. The Teac 25 vrds was sold in Italy in 1996 for the equivalent of roughly 4000$. It now goes for about 1000€ in the 2nd hand market. A lot more expensive than the Pi\speed combo.

We've come a long way from the first time I tried the digi+ vs a CD transport. There is less gap but don't make any mistake... the gap is still there, though reduced. I could write several lines describing it. But since there is still difference in every single aspect of the audiophile foolishness (soundstage width, depth and layering\focus\timber\natural decay\harmonic richness\detail... you just name it) I will spare myself the effort and I will just say that the Teac granted a superior level of performance reality.

Out of curiosity, we gave the teac a run using his conversion... nothing special. A little too much dry and cold for my taste.

Nonetheless since I still hate CDs to listen to music and since I still have not found a cheap device\DDC to play files that would compare well against a very good CD transport I will continue to use the raspberry, which has a superb C\P ratio IMO. But while the speed\raspberry has owned a few good CD transports (not at the level of the teac of course) in the past few weeks, I know that there is still a bloody gap between it and a very good cd transport.

I should be happy that the gap has been reduced a little but I can't help to feel a little disappointed. How can an hi-end CDP from 1996 be still superior in every way to every current device I tried in reading and passing a digital signal to a dac?
What else can be done? @Michael Kelly, any ideas about it?

 

Can you sum up with bullet points in what ways was the TEAC better/worse than the Rpi combo? What DAC was the CDP and Rpi setups being fed into? Coaxial or optical out of the TEAC? What amp was being used downstream? What headphones/speakers?

 

Maybe I didn't explain myself good enough: The Teac was better in every aspect.
Dacs were the Micromega Duo Pro2 and the Counterpoint DA-10.
Coaxial out of the teac. The Amp used downstream was a Micromega IA180. Speakers were Infinity K80.

 

Thanks a lot for recent reviews @Vastx
This means we still have lot to go to get same quality from DIY media player...

 

@Vastx

Nice writeup's!

Have a whole list for you need some time to get it together, but please let me start out...

I've been wondering if going this way (using clocks, not the PLL) that the Speed2 is more sensitive to problems with i2s. The PLL locks on to the signal and can adapt to it and along the way clean up some problems, however it's performance is capped at 50ps jitter, and by "cleaning" might be another limit in performance.

So lets look at optimizing the pi (i2s) itself.

First you're powering it through usb (the pi has an onboard switching power supply) bypass that and power it through GPIO, that's easy on the digi+, you might have to tap into it with the Speed2. I don't have one yet, can't tell the best way to do this.

Second, you're using ethernet... we've already established its horrific with noise, sure the Speed2 is decoupled from this, but probably trashing i2s. Can you go with wifi?

The other pi thread I think we've talked about a lot of the pi side optimizations (using a piZERO, disable HDMI, separate wifi power, RAM cache, etc, etc, etc.) will get into that as we go.

Hope you still have access to the Teac also!

Thanks!

PS I'll do another reply on cables, XLR/BNC, this was getting too long.

 

@Michael Kelly

How can we get the drivers into piCorePlayer--> are you already doing this? If not heads up it's based on tinycore linux, not as easy to do with straight raspian. Should I ask/bug piCore dev's about it? Also is it in the official raspian, or as a PR? piCore will eventually pull from that (probably not for several months however).

Thanks!

 

I was under the impression that a cheap computer with digital out was better then even expensive CD players because of the inherent jitter problems that come with reading the data off the CD. Interesting that your results seem to suggest otherwise.

A couple thoughts:

-The CD player has been optimized to do one thing really well while the RPi is a general purpose device
-Are you using the RPi3? That has bluetooth and wifi and could be adding noise to the card.
-Even with an uber linear power supply the RPi still has chips that need to run at a high frequency (broadcom chip, GPU, USB controller). None of this is present in a CD Player controller.

 

Thanks for the write up, @Vastx . Kind of what I expected. When i get mine in I will compare it with the sonore microrendu, to see if there is, how big the difference will be.

 

What's your thinking on that? I did suspect it may be more sensitive to the i2s from the pi, also wonder about the XLR implementation, BNC may be best here...

 

Despite the difference with the Teac CD player I still think the Pi\speed is a good transport. I need to contextualize the result to other devices and over the next few weeks I'll take it around.
Old hi-fi CDPlayer, despite sometimes with a conversion circuit not up to the task, were highly specialized as a transport using drive mechanisms that are crazy for today mass production. A 1996 teac like the one I used @ 4000$ boasted a philips cdm9, IIRF. Recently at a local technician I saw a current highly praised cary audio $$$ CDPlayer open and the technician told me it used as a drive mechanism... a computer 5,25" cd drive!

I think those old CDPlayers with very good drive mechanisms were highly specialized devices. They were VERY GOOD.
Below them there are several cdplayers that I consider inferior to the raspy as a tranport. They are good cdplayer but not hi-end devices.

This brings me to your comment... the raspy\speed is IMHO totally comparable to commercial mainstream media players from the like of cambridge, marantz etc...
I'd like to compare it to more specialized gear (Auralic, Lumin, soundware...) but I don't know anybody who owns them.

I'll try what you advised. I don't have a pizero. I'll try wifi too.
If I reckon major improvement I'll ask the teac back.
I'm still waiting for a aes\ebu cable to try XLR.

EDIT - also managing vibration is a road I'll try as soon as I'll put the raspy in a case.

I was under the same impression too. Then I listened to them and decided that notebook\desktops are pieces of garbage.
I'm using Pi2, so no wifi and no BT.

I just can't wait for your feedback comparing it to the micro rendu. Do you have it already? What's your take?

 

Just that the pi will still be a reach compared to a good spinner. I dont know about BNC vs XLR yet, though.

 

Came across the thread that you had a Gungnir Multibit at one point, did you end up returning it? Think it would be really useful here!

 

The end game might be a stretch (perfect error/noise free spdif), but what we have now is at a high level, much closer than a stretch! A stock pi/digi+ is the stretch yeah, it sounds like any other common apple airport express, sb touch, etc. i.e. not good.

The way @Vastx has it (ethernet, usb power, OS) needs to be fixed/experimented with.