Raspberry Pi I2S to SPDIF Hat

How does the SQ compaires with the Allo Digione?
I am about to pull the trigger on it but then I found out this DAC which can do both analog & digital.

Thx.

 

I bought a DigiOne for my old man (my dad) before I read about the 502DAC. But I haven't tested his DigiOne in my system because I prefer Toslink. It sounds great in his system though (BNC).

They use digital isolation, as opposed to the transformer isolation of the 502DAC. Allo think transformer isolation adds distortion at the digital output.

They use digital isolation and then re-clock the signal prior to output (if I understand it correctly - I could be wrong).

 

Have spent the last 2 hr reading from pg. 40 to 65. I think I will get the DAC502 instead of DigiOne because TBH I not so sure what exactly I want (i.e. transport or analog) and the DAC502 offer both in a single shield.

May I know if the USD10 off is the only offer code available? Thanks.

 

It was put in place for folks to get the case at no charge since it took us so long to get it out there! There is an upcoming Indiegogo campaign that will offer the 502DAC and 502DAC3, both with a case) at a $20 discount from retail. However, delivery on those units won't be until November.

Cheers,
Michael

 

Does Allo make any claim that this "distortion" actually affects the data (ie the music) being transported? I would love to see hard proof of that!

Cheers,
Michael

 

Good point Michael. I definitely haven't seen that claim from them but that's definitely worth considering.

Btw here's where Allo mentioned this (I didn't make it up): https://community.roonlabs.com/t/allo-digione-board/18564/257

 

502DAC3 is very tempting. When it will show up on Indiegogo? Thx.

 

We're shooting for end of next week. I will post something here when it goes live.

Cheers,
Michael

 

Hi Michael,

After familiarizing myself with the new sound (compared with my Digi+ PRO) these past few days, I put the 5V jumper back in and powered the Pi3 with the stock Pi3 PSU. Photo here: http://imgur.com/a/GIbdN

For others reading this, it's important to note that I'm using Toslink (very well isolated and pretty much immune to RF/EMI) and my DAC's FPGA is supposed to do a pretty good job with jitter reduction, so as I expected, I hear very little difference between using the stock PSU and 2 x Uptone LPS-1's !

If there is a difference, it may be my mind and even then, the difference isn't as much as the Digi+ Pro vs 502DAC (Toslink on both) - to my ears, in my system.

Note, these are just observations, not scientific results (before anyone jumps out).

Regarding the Digi+ Pro vs 502DAC Toslink output, logic tells me anything upstream of the Toslink cable shouldn't make a difference but it's possible that the 502DAC's better NDK clocks and better powered clocks (powered by the ultralow noise LT3042) help to reduce jitter, before the output and before my DAC's FPGA does it's thing with the remaining jitter. Possible. Who knows.

Toslink is definitely my favorite input for my DAC. I may end up using just a single Uptone LPS-1 plugged into the 502DAC board with the jumper removed, and use the other LPS-1 for something else, or give it to my old man (my dad) to use with his Allo board.

Anyway I'm super happy with the 502DAC, either way.

Just a question Michael: please tell me you'll be keeping Toslink with the 502DAC3? Even though I may be the last person on earth using this

The only difference there between 502DAC and 502DAC3 for the Toslink output, would be the MASTER vs SLAVE modes right? The rest of the boards will be essentially the same, as far as the path to the Toslink output is concerned?

Thanks again

 

I am the 2nd (last) person want to use toslink too as I have a spare toslink cable and none RCA.

 

Hehe

 

A good (not great) cable is in the USD35 range so may as well use it instead of buying another cable.

 

Yes, Toslink is on the 502DAC3.

On the 502DAC the PCM5122 is the master and passes the appropriate clocks to the WM8804. On the 502DAC3, the WM8804 is the master and passes the clocks to the PCM1792.

Cheers,
Michael

 

Thanks Michael. You should definitely be super proud of the 502DAC - a very happy customer here.

Regarding the above, if someone is only using the digital outputs, in theory which is supposed to output the lowest jitter - the 502DAC or 502DAC3? And why?

I doubt the differences in jitter can be measured at all but just asking about which you would expect to output the lowest jitter. The WM8804 as the master?

Cheers

 

Questions for the hardware engineers (I am not) -

While I get the apparent appeal of breaking out the clock from the data, what I don't get about I squared S is it still seems like a turtles all the way down problem.

What I mean is the clock still has to be transmitted, so all the same transmission line problems apply no?

It also seems like now you have multiple wires, so doesn't slew still apply?

Really curious.

 

When the WM8804 is the master, MCLK is passed through the chip without modification. When the PCM5122 is the master, the MCLK is routed to both devices directly from the clocks.

In either case there is no processing of the clock so the jitter is solely determined by the NDK clock oscillators. You will get the same results in either situation.

Cheers,
Michael

 

Sending the I2S data over HDMI (using LVDS) eliminates the need to use a downstream PLL circuit to recover the embedded clock. This also eliminates any jitter that will occur from that circuit. However, that jitter is arguably much lower then is audible.

The skew between the clock and data lines is not relevant as long as the clock occurs with sufficient set up and the hold time to sample the data accurately. There is an underlying assumption that the cable will affect the data and the clock in the same way. For a standard HDMI cable this is a very reasonable expectation.

The low cost of a high-quality HDMI cable makes the direct transmission of I2S practical and reasonably priced. It's simply becomes another option that is available depending upon your source card and your downstream equipment.

Cheers,
Michael

 

@Michael Kelly - Thanks for the explanation! Your comment re: assumption explained the skew question perfectly.

 

I would like to ask a favor of you folks that have the 502DAC. We have added a comment section to our web site for it. We would love for you to post your impressions about the 502DAC, good or bad. You can also ask questions as the comments come direct to me. They are not moderated, though if a comment is way off topic or just plain rude we would obviously delete it. Otherwise it's open for your opinions and thoughts. Thanks!

The link is:

http://www.pi2design.com/502dac.html

Cheers,
Michael

 

See you added 502DAC3 as well 8))
Patiently waiting for it.