Something cool for Raspberry Pi/ODROID: I2S/DSD isolator HAT with native DSD decoder

But still applicable for those of us who want to use FIFO,iso,double clock,PCm board with Odroid?

Hi supra,

Absolutely, the u.fl output connectors are designed for audio applications with FIFO KIT. GPIO pins are still available if you prefer DIP connector. It will also work for ODROID without any additional configuration.

Hi Ian,

Excuse me if I'm being dim but I'm unclear from your block diagram. Will both the 3.3v and the 5v feeds to the stacked Rpi HAT DAC be isolated from the Rpi and fed regulated power from your isolator?

Hi Simon,

Yes, both new 5V and new 3.3V power will be fed into RPi DAC HAT that stacks on top of the this isolator board. New power supplies are 100% isolated from PRi. Linear power supply would be highly recommended in this case.

Regards,
Ian
 
Do you have an image of the rear side of the board?
I am creating a sketchup model of it and would like to place components correctly if there are any on the rear side (I take it that there is a header for the pi and one for i2s from the Odroid)?

+bump below

Great project. Following with interest. Will you offer these boards as bare pcb`s or fully/partially populated pcb`s ?
 

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Do you have an image of the rear side of the board?
I am creating a sketchup model of it and would like to place components correctly if there are any on the rear side (I take it that there is a header for the pi and one for i2s from the Odroid)?

+bump below

Hi Gwikse,

That's amazing! Exactly as same as what I want:)

How did you do it? Altium?

Ian
 
Its a 3d sketch with no other function than to illustrate visually the board in a 3d model. I use that for planning my builds. Makes it easier to spot any problems with physicla locations of differnt boards inside an enclosure. I use sketchup for that as it is easy and fast for this sort of thing and has a large collection of models online for download.

I just simply took the picture from your post and made it into a textured material (paint) and painted the surface of a board (copied from a RPI model so that the mounting holes line up) and populated the board with the components that looks correct. When you put up a parts list I will adjust the model so that it is more accurate.

I did the same thing with a lot of other boards. Took the picture of a bare PCB and populated it according to the parts list. That way it is easy to illustrate things without having to take a photo of an actual board.

Anyways, I am looking forward to seing the finished solution, and incorporating it into my DAC solution (with i2c control of an ESS9018).
 
Its a 3d sketch with no other function than to illustrate visually the board in a 3d model. I use that for planning my builds. Makes it easier to spot any problems with physicla locations of differnt boards inside an enclosure. I use sketchup for that as it is easy and fast for this sort of thing and has a large collection of models online for download.

I just simply took the picture from your post and made it into a textured material (paint) and painted the surface of a board (copied from a RPI model so that the mounting holes line up) and populated the board with the components that looks correct. When you put up a parts list I will adjust the model so that it is more accurate.

I did the same thing with a lot of other boards. Took the picture of a bare PCB and populated it according to the parts list. That way it is easy to illustrate things without having to take a photo of an actual board.

Anyways, I am looking forward to seing the finished solution, and incorporating it into my DAC solution (with i2c control of an ESS9018).

Thanks gwikse, it looks very nice. Very smart idea. Maybe I'll try it later.

Good weekend.
Ian
 
Conclusion I2S bus from Pi-circuit board has a lot of jitter, here measuring Comparing the I2S Capabilities of the RPi and Odroid C1+, in ODROID slightly better than of Pi, but all the same level > 1ns (1000ps), Crazy Audio approximately 800ps showed Raspberry Pi I2S output working, сompare Amanero USB board has 2 ps.
Quality I2S bus can correct board, something like a synchronous reclock no frills for the price, such as here Master clock and isolator for the MiniDSP USBStreamer
Obviously, the Ian's FIFO board is the best solution, but it is very expensive compared to PI boards.
ODROID can only operate as a master I2S bus, but the Raspberry Pi can be as a slave on the I2S and Raspberry Pi has Blck input, BeagleBone Black has MCLK input to the SOC.
It may be cheaper to make the isolator/reclock under the scheme, only the idea.
 

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I think many of us are followers of Ian so we already have his FiFO and clock boards (and also I2S to PCM board with reclocking too). I do, so I would not need reclocking added to this board. I just want the isolation and interface with the computer board.

Perhaps reclocking can be added as a daughter board for those that want reclocking.
 
That measns all current DAC HAT, such as HifiBerry DAC, DAC+ and DAC Pro, and meany others, will work with this isolator as if there is without this isolator.

So it will work where the DAC HAT is master for BCLK/LRCK, (eg. HB DAC+ Pro, Digi, Takazine SabreBerry32), feeding those signals from the HAT to the Pi, rather than receiving them from the Pi? (Even with the FPGA DoP->DSD?)
 
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Ian,

Thanks for the great idea!

I for one would love to see Ian do a reclocking HAT too.

Agreed. Ian, when I saw your note about it on your Twitter feed, that is what I thought it was. It makes perfect sense given the high level of jitter on the I2S feeds out of these devices... and since the isolators already add more jitter, I am curious if we'll find that the cure of isolation may not be worth the jitter added UNLESS you do add reclocking. Making this a reclocking HAT (whether natively or via a daughterboard) would do MUCH more to elevate the SQ out of these devices.

But there's more....

So it will work where the DAC HAT is master for BCLK/LRCK, (eg. HB DAC+ Pro, Digi, Takazine SabreBerry32), feeding those signals from the HAT to the Pi, rather than receiving them from the Pi? (Even with the FPGA DoP->DSD?)

This is another key item to consider. While I haven't seen any tests showing that providing a BCLK feed from the DAC HAT reduces the I2S jitter, instinctively it should. Please have your isolation (and hopefully reclocking) HAT also enable the BCLK feed needed by these DACs to perform their best.

Related to that, the HFB DAC+ Pro also needs one or some of the GPIO to communicate with the driver to enable the BCLK master mode. Don't know if the Sabreberry does something similar. But these need to be included too.

Finally, I suspect having your DAC HAT (if it is a reclocking HAT) also generate the BCLK signal or at least reclock it before sending it to the Pi could do just a little more to lower I2S jitter out to the DAC.

I too have your standard I2S reclocker (actually several). But I plan to use them on higher-end DACs... unless your isolation and hopefully reclocking HAT elevates the performance of the Pi/Odroid->Ian Isolation/Reclocking HAT->??? DAC HAT combo to the level I hope and suspect it will, in which case I might just be selling my other reclocking boards!

Greg in Mississippi

P.S. I do have to say I'm getting MUCH better performance out of using a Pi as a source than I expected. My setup using one of your adapter boards to a Soekris DAM DAC is working MUCH better than I expected, not too far behind a setup where I'm feeding a Soekris from an SDTrans384. My two setups using R-Pi DAC HATs, one a basically stock MamboBerry, the other a modified almost beyond recognition HiFiBerry DAC+ Pro, both challenge my best setups. That is why I hope you'll decide to add reclocking to your isolator HAT... given how good these three setups are now, having them fed an isolated and reclocked I2S might make them contenders for my top setup.

Note that I attribute the strong performance of each of these setups to attention to power supplies (all linear) on each, with a dedicated supply powering just the Pi and 1-2 additional (and similarly serious) linear supplies powering the DACs with 2 more available for use with the Soekris when I get around to modifying it.
 
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Hi Ian,

Maybe you could add a normal 5 pins header for I2S output signals for those who want to
connect directly to I2S header of DAC (like me).

Don't think that should be too difficult :)

Btw, any info about a first release date?

Hi Abartels1965,

That's a very good idea. It has a 7 pins I2S header. It's not 5 pins because I want to make it compatible with ODROID. I think it will work for you.

It also has another I2S output in u.fl connectors. You can use it alternatively if you want higher signal quality.

I got the prototype PCB already. But I'm busy preparing open house this weekend. I'll assemble it next week. New update is coming very soon.

Good weekend.
Ian
 
Hi Abartels1965,

That's a very good idea. It has a 7 pins I2S header. It's not 5 pins because I want to make it compatible with ODROID. I think it will work for you.

It also has another I2S output in u.fl connectors. You can use it alternatively if you want higher signal quality.

I got the prototype PCB already. But I'm busy preparing open house this weekend. I'll assemble it next week. New update is coming very soon.

Good weekend.
Ian


Hi Ian,

Sorry for replying so late, very busy at work lately...
Did you have a nice weekend? Open house? That sounds like fun :)

Great you include a header!
For me it would be best since I only use about 1- 1/2" wire direct to DAC.

Not sure though, the new prototype multichannel clock board, is it a HAT for RPI/Odroid, or isn't there any proto yet for RPI/Odroid?


Btw, still have to test FIFO II + Isolator + Dual XO II, still waiting for some
XO's and psu's.

Keep up the good work Ian :)

Alex