Raspberry Pi Coax in?

[MRPR]

H, I'm helping a family member setup a Pi streamer to replace a Chromecast Audio that runs through a cheap generic Dac into a NAD 3020. They already have a LMS Server to do the music (and spotify and castbridge to get the chromecast compatible), and we have a spare Raspberry Pi 3. I think I've decided on this DAC - 'ES9038q2m OPA1612 Op Decoder Digital broadcast board I2S 32bit/384K DSD128 for Raspberry pi' (one of my 'hobbies' is getting china tech) they've sold quite a lot and it has decent reviews and I prefer it to the HifiBerry using the old PCM5122's, I also like that the DAC can have an OLED connected directly to show what it's outputting.

I've done a proof of concept setup using a Pi Zero, a generic pcm5102 $6 dac and an oled (although this showed the 'input' from LMS not the output) and that was already a noticeable upgrade on the CCA/generic DAC so we reckon we can do even better.

The curve ball which seems difficult with nearly any DAC HAT, they want a COAX Digital in so they can feed their CD Player in at a later date, I'm really struggling to find anything to do that, only input stuff I can find is people using usb 3.5mm sound cards but they want a digital in then the Pi DAC can process it, any ideas? The other option which they're not sure about is a USB CD Drive, but they're worried it might not be optimised/balanced properly which could affect playback?

If this works out we'll be doing the same setup in another room to replace a Squeezebox Receiver, that will be fed into a Cyrus III Amp (although they're looking to sell their two PSX-R's as they could do with the cash).

 

[GeorgeWalk]

How about this: https://www.allo.com/sparky/digione.html
Or a Topping D10s?

 

[MRPR]

How about this: https://www.allo.com/sparky/digione.html
Or a Topping D10s?

Thanks for the reply, the digione looks to be output only though, and I'm not sure if it'll clash with another DAC, the Topping D10s only input seems to be USB so I'd still have the same issue of actually getting the signal into the Pi.

 

[somebodyelse]

I'm not sure I've quite understood the requirements, but here goes...

Have a look at the HifiBerry Digi+ I/O and DAC+ DSP but make sure to check up on what the limitations are. As I understand it the core of the problem you face is that the Pi only supports a single I2S channel so you can't have both input and output at the same time. I gather there is a board that's managed more channels by getting creative, but it sometimes loses sync and strange things happen. The DAC on the DAC+ DSP isn't great, but if you're up to some low level work there's an I2S/TDM port available - barely documented so you'd need a pretty good idea of what you're doing. In this case you'd be routing the audio entirely in the DSP, so the Pi's I2S limitation isn't an issue. Beyond that you can start looking at USB interfaces like the minidsp usbstreamer.
Also from audiophonics this one can take inputs from spdif, toslink, USB and pi.

 

[panulee]

damn, I was just commenting on another thread that I wanted a similar solution to what you linked to at the end...
Has this board been reviewed by anyone around here? thanks!
-edit: just found the review

Would you recommend a decent AMP module to go with all this and somehow fit on top? Thanks

 

[MRPR]

I'm not sure I've quite understood the requirements, but here goes...

Have a look at the HifiBerry Digi+ I/O and DAC+ DSP but make sure to check up on what the limitations are. As I understand it the core of the problem you face is that the Pi only supports a single I2S channel so you can't have both input and output at the same time. I gather there is a board that's managed more channels by getting creative, but it sometimes loses sync and strange things happen. The DAC on the DAC+ DSP isn't great, but if you're up to some low level work there's an I2S/TDM port available - barely documented so you'd need a pretty good idea of what you're doing. In this case you'd be routing the audio entirely in the DSP, so the Pi's I2S limitation isn't an issue. Beyond that you can start looking at USB interfaces like the minidsp usbstreamer.
Also from audiophonics this one can take inputs from spdif, toslink, USB and pi.

Basically they want to run a digital coax output from the CD player into the Pi then the Pi DAC can do the decoding and output, instead of the DAC in the cd player. It seems though it's much more complicated than we presumed, although I'm not sure why, it's essentially just a usb soundcard with coax input.

 

[somebodyelse]

I wonder if any of the ESS based DAC hats include an spdif input? The ESS has a pin for it - see the Tone Board schematic for an example of using both the coax and I2C - the Pi would essentially take the place of the XMOS on the Tone Board. You wouldn't have access to the spdif from the Pi though, so no chance to do any processing for room correction if that's what you were after.

I'm not aware of many simple USB soundcards with coax input - the MiniDSP is about as close as I've seen and that's toslink rather than coax - you'd have to add a few components to convert it. Technically it's not that complex, but usually it's just part of something bigger like a multichannel recording interface or the ridiculously priced U-DIO8. I guess there's just no perceived market for an spdif to usb adapter the way there is for the other direction.

 

[MRPR]

So we ended up doing a complete about turn and ordered a Topping E30 so we can run a Pi into it via USB although we'll be seeing how we get on with a CCA over optical, and can also connect a CD Player via COAX. Got a decent deal stacking coupons on Aliexpress so $100 (£76) vs the normal UK price of $145 (£110). We'll see how we get on.

Thanks for all the replies, we might end up getting another Pi with the DAC I originally listed as well eventually for another room, I'll provide feedback when we do but given the current global situation they're trying to cut down on spending so just the E30 for now.

 

[Jungstar]

https://www.audiophonics.fr/en/dac-...p-12795.html?search_query=9038&fast_search=fs

This one has SPDIF in but I have heard there might be some lag and also you need the volume controller or something to change the input

 

[Jungstar]

also,this one
https://www.audiophonics.fr/en/diy-...p-12557.html?search_query=9038&fast_search=fs

 

[Nango]

Khadas TB VIM Version has Coax in as well.

 

[somebodyelse]

Khadas TB VIM Version has Coax in as well.

That won't work with a Pi though - the coax in is routed to a pin on the header by switches controlled via two other header pins. It's for use with Khadas' VIM SBCs which have different pinouts to the Pi and include a pin for spdif input.

 

[Specialcause]

the Pi only supports a single I2S channel so you can't have both input and output at the same time.

One way to connect CD player to Pi is by feeding analogue output to a Hifiberry DAC + ADC (which both Moode and Volumio support). I presume that would avoid the problem of the single I2S channel, which you would have when using a Hifiberry Digi I/O HAT?

I currently use parametric EQ (via FusionDSP in Volumio) when playing local files. Would my PEQ filters also be applied once the analogue signal from CD player is converted to digital by the Hifiberry DAC + ADC?

If the answer is yes, are there any problems I’m likely to encounter ( apart from needing Volumio premium subscription)? Are there other HATs I could consider, or suggestions for achieving same goal: applying PEQ filters to the output from CD player (without adding a big box like Behringer DEQ2496)

 

[ezublab]

It seems that any input in Volumio goes through the same signal path.
So in your case, Eq should be applied to your input as multiroom.