Raspberry Pi I2S to SPDIF Hat

I always used photobucket. They provide image links for forums. Set up your account,upload your photos and use the image links in your thread

 

Anybody have anything to say about their loaners?

 

Curoius how far off these SPDIF hats are to market. I think this would be the best way to go with my Modi Multibit. My Raspberry PI is on the way in the mail. Want to get it sounding its best!
Thanks!

 

Second report of the 502DAC HAT from Pi2Design.

It is of no doubt to me that the digital streaming is the future for digital music playback. My first streaming device was a Logitech Squeezebox Touch back in 2012. Unfortunately, only six years after Logitech acquired Slimdevice, Logitech decided to end the project and stopped the production of the Touch in 2012. Since then, I have been looking for alternatives.

There are three approaches for streaming music. The first approach and most popular approach is using a USB/SPDIF converter. It can be either a circuitry within a USB DAC or an external board/box, which is usually called a DDC (digital digital converter). The second approach is the so-called AOIP (audio over IP). The music data are transferred via wired local area network (LAN). The REDNET 3 was rated at a score of 220 by rb2013 (see weblink below). The LAN signals are "isolated" in nature, because there is no ground wire between the devices. The third approach is the SoC (system on chip, for example the raspberry pi) + HAT approach. The SoC serves as a controller/streamer; the HAT converts the Pi's I2S signals to SPDIF.

For reference, here is a great ranking list for many streaming setups from [email protected]. (http://www.head-fi.org/t/829639/usb...-usb-ethernet-chain-beats-all-at-least-for-me). I copied part of the list below. The rating helped me to better understand/estimate the sound of the gears that I have not owned.

Ultra USB chain (details too long to list): 370
REDNET 3/Curious Power Cord: 220
Singxer F-1 DC30W/Curious/Recovery/DCiPur/iPur2: 125
Singxer F-1 Stock feed: 110
Melodious MX-U8 stock : 81
Gustard U12 stock: 72
Audiophileo 2 USB Power: 50
M2Tech Hiface: 40

The USB chains can be quite costly. For example, the above mentioned Curious USB cable costs $120 or more. The Recovery is $199. The Startech combo in the Ultra USB chain costs $480 after discount.

IMHO, a nice sounding DDC should include the following elements. (1) Two high precision clocks (oscillators), one for the 44.1k/88.2k/176.4k data conversion and the other one for 48k/96k/192k/384k. (2) Good linear regulation at multiple stages. For example, the Melodious MX-U8 has 9 linear power regulation chips. Especially, an ultralow-noise linear regulator should be used for these two oscillators. The ADP150 regulators were used on both WaveIO board and F-1 XMOS board (<9uV). The LT3042 was used on Pi 502DAC HAT (<1uVRMS). (3) Good isolation. The +5V on the board should be isolated from the +5V of the upstream USB device (PC, MAC, or SoC). The isolation can be done on the circuit board (separated PS). The USB "decrapifiers" can be used for +5V isolation as well (W4S Recovery USB reclocker, Uptone Regan amber, or Schiit decrapifier).

My first experience on the DDCs was the Hiface Two. It brought my original Logitech Squeezebox Touch (LST) to a new level in terms of clarity. But it has been always sounded a little lean and digitized to me. Later I started to use a Cubietruck running Linux and squeezelite as my streaming device. I did not choose Raspberry Pi because the LAN and all usb ports on the Pi share one physical on-chip usb channel, which may cause "traffic jam" (both incoming music data and the outgoing USB audio data). I chose Cubietruck because it had separated on-chip channels for the gigabit LAN port and the USB ports. When connected to the Cubietruck, the stock Gustard U12 had better bass than the Hiface Two and brought up a broader and deeper soundstage. It was a significant upgrade compared to Hiface Two. But the Gustard U12 had a strange "dark" sounding signature. The image was also a little vague. The stock Melodious MX-U8 sounded very good with PC but I could not get it work with Linux. So I let it go. It sounded better than Gustard U12 when both connected to PC. When supplied with a regulated LPS, the WaveIO exhibited a very musical sound signature especially a warm mid-range. The mid-range from the WaveIO was almost like "colored" in a nice musical way. Unfortunately, it sounded a little grainy after long listening session. Still, I had a hard time ranking the WaveIO and the unmodified F-1 XMOS DDC. Later I upgraded the F-1 following this post (http://www.head-fi.org/t/803111/xmos-xu208-usb-bridges-the-latest-gen-has-arrived/3090. Thank you [email protected]) I also replaced the RCA SPDIF output with a Neutrik 75 ohm BNC socket. Once I finished the modifications on my F-1 board, it won in every aspect over the WaveIO. The modified F-1 sounded neutral, detailed, and non-fatiguing. The sound stage was broader than that from WaveIO.

In addition to SoC, I have tried laptops (Lenovo Thinkpad T440s, et cetera) with a couple of DDCs. When used the same DDC, my laptops powered by the stock switch mode PS resulted in the worst sound. They sounded less digitized when running with the internal li-ion battery. I have also tried a W4S Recovery USB reclocker using an external LPS in the USB chain. The USB reclocker improved the sound from the laptop significantly but did subtle improvement to the LPS powered SoC (in my case a Cubietruck). I assumed that the SoC powered with a LPS had pretty "clean" USB signals thus less improvement. In the end, I prefer the sound from my SoC setup for music streaming over my laptops. This is only to my ears in my system, and most of my music files are 44.1k wav or flac formats. I also did not spend too much time tweaking the settings. So YMMV. I thought that I would be all set with my Cubietruck music streamer + the F-1 XMOS USB/SPDIF converter for a while.

Well, it wasn't long before I saw the design of 502DAC HAT. I have had an official Wolfson DAC Pi HAT for years. The spdif output from the Wolfson DAC cannot compare to my F-1 XMOS. No surprise as it has only one oscillator for clocking, and the Wolfson DAC takes power supply from the Pi board. It was impressive and promising as to what it was designed for, but it was not good enough for a Hi-Fi system. Michael's 502DAC board comes with two NDK NZ2520SD oscillators and a ultra-low noise linear regulator for these oscillators. All the important elements to me had been addressed in the design. I was excited about it and requested a testing unit. The testing board I received did not come with the DAC analog output. Thus I only tested the BNC SPDIF output. It is perfectly fine to use a Pi with the HAT because the I2S signals come from the GPIOs on Pi, which means that the incoming music data and the outgoing I2S signals are separated at the hardware level.

First, I listened when 502DAC board took power from Pi. The Pi was powered by a generic switch mode PS. I immediately heard more details, broader sound stages, better focus and instrument separation. I did not noticed a significant "break-in" period, might have been some changes in the first 10 hours or so. Two things struck me immediately. One was the now-obvious decay of vocal voices and the instruments as if suddenly I started to realize that the music was recorded in a room instead of on an open space. The second thing that 502DAC can do and the F-1 cannot was that the 502DAC brought out a 3-D image where I could "feel" the height of the vocal voice and other instruments. Then I tried a good LPS for 502DAC board (a LT1086 or LM317 will be good enough), the sound improved significantly. Although the details and micro dynamics did not improve further, the tracing "digitized" sound signature (when the 502DAC take +5V power from the Pi) went away. I could listen to the music this way for hours without ear fatiguing. Oh man, I started to like the sound of my B&W nautilus 805 speakers which I thought they were a little analytical. Then I tried to power the Pi main board with another regulated LPS instead of the switch mode PS, there was a noticeable improvement with even less "digital" sound signature and a darker background. What about the bass? Bass was better than the already-great bass from F-1 XMOS. I still like my F-1 XMOS, it is pretty musical. Just the 502DAC HAT sounded even better with a lot more details, micro dynamics, and more authority in bass.

The Pi + 502DAC sounded so good that I decided to add a touch screen and made an aluminum case for the combo. It looks like a Logitech Squeeze Touch to me, with a more than 10 times faster processor and a four times higher resolution screen. Now I have a digital box looks nice and sounds the best (so far) in my system. I attached pictures of the Pi+502DAC player and the modified F-1 XMOS in a recycled aluminum case.

Thank you Michael.

Happy listening

Testing system: Raspberry Pi3 running piCorePlayer 3.02, Pi2Design's 502DAC digital audio HAT, two +5V 1A LT1086 regulated LPS, modified F-1 XMOS, Cubietruck running Linux, LMS 7.9, and Squeezelite 1.8. Bluejean 75 ohm BNC cable, Schiit Gungnir Multibit, DIY tube line stage (6 12AX7 tubes, two separated regulated B+ supply), Dynaco ST-70 with VTA driver board, B&W Nautilus 805 speakers on stock stands half filled with steel shot, LAT international Bi-wire speaker cables, Monster HTS 3500 MKII Reference PowerCenter.

 

@hifiandrun impressive write-up.

 

@hifiandrun

So your previous system is worth 125 points?
How does it compare with Gungnir Multibit usb to rpi?

What the hell is this: DIY tube line stage (6 12AX7 tubes, two separated regulated B+ supply)?

 

I could only guess that the modified F-1 is around 120 - 130 points. I don't have the Curious USB cable. But I have to say that the mods improved the sound quite a bit with the DC-DC converter removed, a modified F-1 is like a poor man's Singxer SU-1 without AES and HDMI connections. To my knowledge, rb2013 only used the stock F-1.

I would rate ~ 40-50 for the Gungnir Multibit usb. I sold my Hiface Two, but if my memory serve, the Gungnir Multibit USB has better mid-range but worse details compared to Hiface Two. As I mentioned in my report, rPi is not a good choice for streaming music through USB because the shared usb channel (say usb hub to be more precise). Any other Pi alternative can do better job for the USB audio.

It was a "home-brew" mimicking the Jadis JP200 design. Three stages of amplification in parallel configuration for two channels, single-ended, thus 6 tubes.

 

Hi Michael, the buzz that I experienced would only occur when the official Pi touch screen was controlled by Jivelite in piCorePlayer, in addition to that it only occurred after I pushed the on-screen touch button (on/off icon) to dim the screen. No buzz when the screen disconnected. Even when the screen was connected, there was no buzz in any other circumstances. I haven't found any other situation that would trigger the buzz / high pitch sound. Anything else that you would like me to try?
Best,

 

@hifiandrun - thanks for the detailed write up. Very interesting. I am considering Raspberry Pi as a Squeezebox replacement. What display are you using?

 

The touch screen is the official 7'' LCD for Pi. (https://www.element14.com/community/docs/DOC-78156/l/raspberry-pi-7-touchscreen-display)
The enclosure for the screen is from Amazon. I like it, just be careful when fitting the edges of the display into the case cause it fits very tight. (https://www.amazon.com/Eleduino-Raspberry-Official-Touchscreen-Display/dp/B01FZ2RJN8)

 

We have one great report of the SPD2, one report of a high pitch buzz, what about the other 4 people who received a tester?

 

Took me a while to get a power supply built for powering the 502DAC, but I got it built now and am working on some evaluation. Will get a review up ASAP. For now, I will say that it sounds incredibly good feeding into Schiit Yggdrasil using AES/EBU (as compared to direct USB out from my laptop).

 

Mine was stuck in customs over the holidays. Hopefully can gather my thoughts about it in the coming weeks. No buzz on my sample.

 

My item is still handled by customs since 16th December. Hope I'll have good news in next weeks. I already tried to contact local post office but they weren't able to give me details.

 

Can you make a version with ATT Fiber output, as well?

 

Hi Michael,

Quick question on the i2s MCLK:

Do you have any control over the clock division? If you do not know it's probably set in the driver, that sets registers in the wm8804 (or pcm5122)- With your board the 44.1/48 sample rates are using the full 22/24Mhz (512Fs). The Hifiberry Digi+ PRO divides this down to 11/12 (256Fs) even tho it also uses 22/24MHz crystals.

Doing research on the Schiit Multibit i2s, turns out it's expecting 11/12 (256Fs) for 44.1 and 48.

I'll talk a bit with Daniel at hifiberry as to why he did it that way... maybe more compatible, better signal since it's slower?

Thanks!!

 

piCorePlayer 3.10 audio came out. I tried it, but in my system, the older 3.02 version sounded better - clearer and more relaxed. Not sure why.

 

We use the same DAC, PCM5122 and select the two clocks using the same PCM5122 GPIO as the HiFiBerry DAC PRO+. The DIGI+ uses the WM8804 transmitter in master mode and Raspberry Pi GPIO to select the clocks. For whatever reason they made them different. Maybe they did that to accommodate the Schiit?

Sorry for my now usual disappearing act. Was in the middle of designing and bringing up two new tube amps. Totally consuming. Plus my alerts were somehow turned off!

Cheers,
Michael

 

Quick question, are you connecting to the analog outputs? They were wired wrong and will cause buzzing. Please do not use.

Cheers,
Michael

P.S. 502DAC P2 PCB's are here:





Now we just need to get them on the pick and place machine later this week!

 

Can the RCA connectors be fixed on the test boards?