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Review and Measurements of Pi 2 Design 502DAC

amirm

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#1
This is a review and measurements of Pi 2 Design's 502DAC. I was kindly sent by designer and forum member @Michael Kelly. It retails for 109 from his website. He was kind enough to send me a complete system with the requisite Raspberry Pi and Volumio audio operating system. As a result, the unit was turnkey in operation:

Pi 2 Design 502DAC DAC review and Measurement.jpg

I powered it up using a single supply (it allows for dual supplies). Connect an Ethernet cable or use WiFi to get a networked DAC and S/PDIF output.

In my case, since Volumio only supports 16-bit audio from my Roon player (through airplay), I resorted to playing my test files from the USB thumb drive (red and black stick). DietPi supports Roon's RAAT protocol by the way.

Support from Michael has been excellent which is always a plus in my book. He told me that the main application for this device is using it as a networked S/PDIF & AES/EBU interface (to your own DAC). The included analog outputs are a bonus. Toslink is also supported.

Let's measure it and see how she does.

Measurements
I started with measuring the spectrum of jitter and noise from its BNC output:
Pi 2 Design 502DAC SPDIF Jitter Measurement.png


Here, I am comparing it to the Allo Signature. Compared to that, we have a series of spikes but their levels are exceptionally low at just 1 picoseconds. Comparing to budget desktop products like the Topping D10 (inset), this is excellent performance. This is even more so seeing how this is a networked solution (and hence more opportunity for noise pollution) than a simpler DAC.

Testing the internal DAC using our usual dashboard view we get:

Pi 2 Design 502DAC dashboard Measurement.png


Output is nice at 2 volts. Alas, distortion levels are high relative to desktop solutions and top of the line Pi HATs. SINAD of 86 dB puts it in forth tier of products I have tested:
Pi 2 Design 502DAC SINAD Measurement.png


Measuring jitter from the analog output we get:


Pi 2 Design 502DAC Jitter Measurement.png

Very clean output although the noise floor is higher than more expensive solutions (e.g. Allo Katana).

Conclusions
As a networked digital audio output solution, the Pi 2 Design 502DAC accomplishes its purpose. It has very good jitter response, besting budget S/PDIF converters that don't have networked interfaces. In that specific application, combined with great support from Michael, I recommend this solution as more budget friendly than likes of Allo Signature.

For analog output, the 502DAC works but you can do much better with other solutions. It is nice to have it though for "confidence monitoring" as one uses it with digital outputs.

As always, questions, comments, corrections, etc. are welcome.

-----
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#2
I also own the product which is a good little device especially when using it as a network transport.
 
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#3
@amirm Following my comment about reasonably price s/pdif outputs on the allo thread, this is helpful. But this would be very expensive for a digital output at 109 (us dollars?). Sorry to be picky but the presentation of the digital output measurement is a bit confusing since it isn't easy to read which device is which (at least on my screen). It looks as though the allo sig has a big spike at 12kHz or so- is there any reason for this? This and the spike at 36kHz are much worse than any component on the pi2design. I am also a bit cofused about using the bnc rather than ordinary coax s/pdif output on the pi2 -is tha the only connector it has?
Finally (sorry) if measuring a digital output then I wonder whether it might be useful to measure the absolute cock rate of the output and any long term drift as these will be material to how easy it will be for a dac to provide a perfect output (ie for some types of dac, whether it can rely on a buffer and a fixed clock or whether it will have to track changes in the input flow)
I would be happy to order something like this as a sensible reference https://www.hifiberry.com/shop/boards/hifiberry-digi-pro/
 
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#4
@amirm Following my comment about reasonably price s/pdif outputs on the allo thread, this is helpful. But this would be very expensive for a digital output at 109 (us dollars?). Sorry to be picky but the presentation of the digital output measurement is a bit confusing since it isn't easy to read which device is which (at least on my screen). It looks as though the allo sig has a big spike at 12kHz or so- is there any reason for this? This and the spike at 36kHz are much worse than any component on the pi2design. I am also a bit cofused about using the bnc rather than ordinary coax s/pdif output on the pi2 -is tha the only connector it has?
Finally (sorry) if measuring a digital output then I wonder whether it might be useful to measure the absolute cock rate of the output and any long term drift as these will be material to how easy it will be for a dac to provide a perfect output (ie for some types of dac, whether it can rely on a buffer and a fixed clock or whether it will have to track changes in the input flow)
I would be happy to order something like this as a sensible reference https://www.hifiberry.com/shop/boards/hifiberry-digi-pro/
502DAC is both digi (more input then hifiberry) and DAC and should out perform the hifiberry.
 
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#5
502DAC is both digi (more input then hifiberry) and DAC and should out perform the hifiberry.
leaving aside that it doesn't perform well as a dac, why can it be expected to outperfom the hifiberry for s/pdif?
Assuming it does, any idea whether they are thinking of providing it witghout the dac at a lower price.
 
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#6
leaving aside that it doesn't perform well as a dac, why can it be expected to outperfom the hifiberry for s/pdif?
Assuming it does, any idea whether they are thinking of providing it witghout the dac at a lower price.
I tell you why. I orginially use it as digi but I changed my setup and it allows me to use it as a dac in my bedroom. Otherwise it will be just sitting in my drawer.

If cheapness is what you are looking for then get the hifi berry (keep in mind you still need to buy the rpi3 & etc) or just get the Topping D10.
 
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#7
I tell you why. I orginially use it as digi but I changed my setup and it allows me to use it as a dac in my bedroom. Otherwise it will be just sitting in my drawer.

If cheapness is what you are looking for then get the hifi berry (keep in mind you still need to buy the rpi3 & etc) or just get the Topping D10.
I tell you why. I orginially use it as digi but I changed my setup and it allows me to use it as a dac in my bedroom. Otherwise it will be just sitting in my drawer.

If cheapness is what you are looking for then get the hifi berry (keep in mind you still need to buy the rpi3 & etc) or just get the Topping D10.
Perhaps we are at cross purposes. I was interested in the question of what would be the best pi s/pdif output at reasonable cost. I'm not especially interested in external usb dacs, perhaps a bit more so in pi hat dacs..
That said the topping does seem like a good product. I am however unclear about how to interpret its measurements as a I assume they are taken with roon powered pc as usb source. It would be interesting to see what low price dacs make of a pi as usb source as one would expect that to be pretty poor (shared usb bus).
 
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#8
Perhaps we are at cross purposes. I was interested in the question of what would be the best pi s/pdif output at reasonable cost. I'm not especially interested in external usb dacs, perhaps a bit more so in pi hat dacs..
That said the topping does seem like a good product. I am however unclear about how to interpret its measurements as a I assume they are taken with roon powered pc as usb source. It would be interesting to see what low price dacs make of a pi as usb source as one would expect that to be pretty poor (shared usb bus).
Topping D10 can do usb to spdif out.

I had tested briefly 502DAC spdif out and iFi iOne spdif out (but USB to spdif) both to Topping DX7s. 502DAC won.
 
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#10
Amir,
What additional digital tests are possible with Roon? It shouldn't be too difficult for me to make you an SD card with DietPi on it. You need only select Hifiberry DAC+ Pro to use our 502DAC.

Michael
Pi 2 Design
 

amirm

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#11
Amir,
What additional digital tests are possible with Roon? It shouldn't be too difficult for me to make you an SD card with DietPi on it. You need only select Hifiberry DAC+ Pro to use our 502DAC.

Michael
Pi 2 Design
It is all very tedious but I can measure dynamic range. And IMD but not as a graph but a few sample points.

Strangely my new AP analyzer is less capable than my older one. It can't asynchronously measure anything that its level changes.

On Roon and Dietpi, I am OK with the flash card playback on the Volumio you sent me. It is a bit slower in having to copy files to it but it is not worth the hassle of sending me a new card.
 
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#13
Hi guys!
Separate salute Amirm and Michael.
Yesterday I had the opportunity to properly connect the Allo Digione Signature to Two very high quality audio Linear Power Supplies.
I also have a similar layout for the 502.
Amirm of all types of food you have chosen the worst. Hence the results.
Michael, I'm the one who told you how, how to eliminate overheating of the 502 PRO board, I'm sorry that you took it off sales.
I will make a separate report on 502 PRO.
I found errors in 502, eliminated them. In terms of sound, this is now the top device from the world of ARM.
Michael I say thank you!
Just don't ask me now what I did. This work and two years.
As now 502 sounds does not sound Allo Digione Signature.
This is a miracle!

two layouts in the photo:



IMG_20181012_234101.jpg
IMG_20180929_174319.jpg
 
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#14
I am not sure what to say. Um.. thanks! I'm glad you are happy. Of course I would love to know what you did (other than use the external linear supplies), but I'm not asking, just saying! ;)
 
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#15
Hello Michael!

Michael, I read the entire SBAF forum on the 502 map starting on the 1st page.
You are an amazing person and well done, that having no experience, you took it and made such a beautiful Sound!
But on the forum you do not write the whole truth (you know what I'm telling you)

I made a great reference source, and my friend is a programmer (he lives in another country) for 2 years did the Software for it from the kernel and continues to do it further.
For example, yesterday we made it even better and the work was finished at 04 AM between Friday and Saturday. Over these 2 years we have not been afraid to say a reference Sound. And everything that was put up against him on head-on testing was simpler and worse by Sound.
Nobody outplayed our source, nobody.
I will repeat on any exhibition that I have never heard such a Sound anywhere!

I have a point of reference Sound.

I describe it to you, so that you would understand that we are sick people in Sound, and for us it is just as important as air, not Michael's money, but air. For the money we will come back.

Listening to your board, I saw its great potential, but unfortunately I understood that it was not fully disclosed. The sound needed some work.

And I decided to rectify the situation, for a long time I wanted to do it, but did not reach out.

Through your friend, whom you promised to send the generators for the 4th revision (do not forget about it), I asked you to give me a 502 diagram scheme, which would make it easier for me to upgrade. But you didn't answer this question.

I spent one full day to understand all the details of your board.

Then I took about 6 steps of the upgrade, each time listening to the result step by step. It was difficult and interesting, damn it)
But only one step out of 6 worked for the good.
And I removed the turbidity and veil from all Sounds.
Without affecting the tonal balance and resolution.
The scene became deeper the Sound became cleaner, less debris.

I still had two ideas that I did and listened to yesterday, the Sound has improved even more.
Now I can say that everything was done correctly for the gland.
But I am a maximalist and this is not enough for me.

You can still significantly improve the sound, but here you need to make software. And this is half the success in Sound.
I am listening to Tidal through Roon and having the Sound standard, I understand that there is a lot of work ahead.
Michael want to help create a better Sound ARM?
To do this, I need to create an ideal proto-type for the hardware and send it to my programmer. I Will Make 4 Linear Power Supplies. 3 will go to raspberry Pi 3b and one to 502. I will upgrade 502 to collect the source and send it for tests and work.
For this, I ask you to send me one 502, it will be your help. Are you with us?
The software will be free for all.
My goal is a good Sound for everyone, including non-rich people.
It is necessary to inculcate in people the love of music and not only through money.

Once I bought from you on Kickstart 502 like for USD $ 56.00, for me it was a shock to see the price in USD $ 99.00 and finally you surprised me with the price of USD $ 109.00
I understand business and all that .... but where is the respect for the members of the forum who helped you? People come to the forums, I hope to save money, they help you in tests and in advertising and popularizing your card, and when this happens you expose such prices.
This is true?
You write that you would like to know the details of the upgrade, but if I tell you this, you will hear a new Sound and you will want to raise the price even more, since it will sound better and easier than the Allo card with the Signature of USD $ 235.00

Best regards,
Bason
 
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#16
Hello Michael!

Michael, I read the entire SBAF forum on the 502 map starting on the 1st page.
You are an amazing person and well done, that having no experience, you took it and made such a beautiful Sound!
But on the forum you do not write the whole truth (you know what I'm telling you)

I made a great reference source, and my friend is a programmer (he lives in another country) for 2 years did the Software for it from the kernel and continues to do it further.
For example, yesterday we made it even better and the work was finished at 04 AM between Friday and Saturday. Over these 2 years we have not been afraid to say a reference Sound. And everything that was put up against him on head-on testing was simpler and worse by Sound.
Nobody outplayed our source, nobody.
I will repeat on any exhibition that I have never heard such a Sound anywhere!

I have a point of reference Sound.

I describe it to you, so that you would understand that we are sick people in Sound, and for us it is just as important as air, not Michael's money, but air. For the money we will come back.

Listening to your board, I saw its great potential, but unfortunately I understood that it was not fully disclosed. The sound needed some work.

And I decided to rectify the situation, for a long time I wanted to do it, but did not reach out.

Through your friend, whom you promised to send the generators for the 4th revision (do not forget about it), I asked you to give me a 502 diagram scheme, which would make it easier for me to upgrade. But you didn't answer this question.

I spent one full day to understand all the details of your board.

Then I took about 6 steps of the upgrade, each time listening to the result step by step. It was difficult and interesting, damn it)
But only one step out of 6 worked for the good.
And I removed the turbidity and veil from all Sounds.
Without affecting the tonal balance and resolution.
The scene became deeper the Sound became cleaner, less debris.

I still had two ideas that I did and listened to yesterday, the Sound has improved even more.
Now I can say that everything was done correctly for the gland.
But I am a maximalist and this is not enough for me.

You can still significantly improve the sound, but here you need to make software. And this is half the success in Sound.
I am listening to Tidal through Roon and having the Sound standard, I understand that there is a lot of work ahead.
Michael want to help create a better Sound ARM?
To do this, I need to create an ideal proto-type for the hardware and send it to my programmer. I Will Make 4 Linear Power Supplies. 3 will go to raspberry Pi 3b and one to 502 fee. I will upgrade 502 to collect the source and send it for tests and work.
For this, I ask you to send me one 502, it will be your help. Are you with us?
The software will be free for all.
My goal is a good Sound for everyone, including non-rich people.
It is necessary to inculcate in people the love of music and not only through money.

Once I bought from you on Kickstart 502 like for USD $ 56.00, for me it was a shock to see the price in USD $ 99.00 and finally you surprised me with the price of USD $ 109.00
I understand business and all that .... but where is the respect for the members of the forum who helped you? People come to the forums, I hope to save money, they help you in tests and in advertising and popularizing your card, and when this happens you expose such prices.
This is true?
You write that you would like to know the details of the upgrade, but if I tell you this, you will hear a new Sound and you will want to raise the price even more, since it will sound better and easier than the Alo card with the Signature of USD $ 235.00

Best regards,
Bason
We should probably have this discussion directly. I am more than happy to send you the unit for you to work your magic on! I just don’t think the rest of the forum readers will be as interested in the back-and-forth as they will be in the end result. Which either you or I will certainly post.

You can send an email to [email protected] to begin our discussion.
 
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