i2s DAC solutions

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IDM
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Post by IDM » Sat Apr 11, 2015 8:40 pm

I have done some reading round on the BBB based on Ray’s comments and I think the main thing that puts me off at the moment is the BBB apparent fragility. I was aware that it can be damaged by inadvertent powering down of the board. However, reading the notes on the Botic linux distro it says that the BBB should not be directly connected to a DAC via I2S for fear of damaging the BBB! I know Ray recommends the reclocker which would avoid these issues, but it does seem like quite an undertaking to get a BBB safely working and not a beginner’s project!

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Ray P
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Post by Ray P » Sat Apr 11, 2015 9:49 pm

Ian, yes, there is a shortcoming in the BBB power management that can kill the BBB but as far as I am aware the issue isn't about connecting a DAC via I2S per se. I believe there are two scenarios to be avoided;

1. If 3.3V is applied to the header pins of a BBB before it has booted it can kill the BBB. This is an issue when you feed into the BBB, such as an external clock signal. To I2S connect a DAC directly to the BBB header the signals are all outgoing so not an issue but then you miss out on the advantages of the external clocking. The reclocker that creates the issue by feeding the BBB a clock signal is also the solution as the BBB side of it's isolators are powered from the BBB header; until the BBB has booted there is no power to one half of the isolators so no signal can actually get to the BBB.

2. An uncontrolled shutdown of the BBB (such as just yanking the power lead out or a powercut) can (but not always) kill the BBB. I currently manage this by shutting down the BBB before powering down the DAC (just a simple press of a momentary action switch triggers a controlled shutdown) but the daughter board I'm waiting on for DSD functionality also includes additional power management and the ability to run the BBB on a battery with automatic shutdown if voltage drops below a threshold.

Hopefully the BBB group will resolve the power management issues soon.

Ray

Neal
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Post by Neal » Sun Apr 12, 2015 12:04 am

IDM wrote:Some really interesting stuff. I didn't know there were so many different players available, I will have to try some of them at some point.

Currently I just use Volumio with a UPnP music server (Asset on another raspberry pi, or minimserver also on a raspberry pi). The kids sometimes use the airplay feature of volumio which also behaves fine.

How do you find the audio quality of the pi as the I2S source?

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Ian
The quality is v.good I'll stick my neck out and say it could be the best I've heard from my system. Eliminating the SPDIF interface seems to be a large step forward.

I've installed Moode tonight and it's better than Volumio and doesn't exhibit the same bugs...
Only the Sith deal in absolutes.

Tony Moore
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Post by Tony Moore » Sun Apr 12, 2015 10:54 am

Yes, SPDiff is a very poor method of transferring such time sensitive data. Far better would be I2S transferred over LVDS lines.

I was going to implement LVDS when I built my streamer a few years back but in the end it sounded fine with just the short wire interconnections. I reclock the signals on a board directly above the 1541A, no more than 1" of wire between them so I think I'm ok.

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Nick
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Post by Nick » Sun Apr 12, 2015 2:40 pm

Tony Moore wrote:Yes, SPDiff is a very poor method of transferring such time sensitive data. Far better would be I2S transferred over LVDS lines.

I was going to implement LVDS when I built my streamer a few years back but in the end it sounded fine with just the short wire interconnections. I reclock the signals on a board directly above the 1541A, no more than 1" of wire between them so I think I'm ok.
I would argue that as a transfer method USB or ethernet is far better, it doesn't have to worry about clocking as it can be buffered and reclocked at the receiver, and being two way if needed you can resend lost data/
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Tony Moore
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Post by Tony Moore » Sun Apr 12, 2015 5:33 pm

Between the receiving device and the DAC chip I was intending to say, in the context of the previous comments. There again, if the receiving device is close enough then you don't need the LVDS.

But yes, USB or Ethernet are far better choices these days than SPdif.

jmansion
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Re: i2s DAC solutions

Post by jmansion » Sun Nov 22, 2015 3:23 pm

Talking of i1s, has anyone tried either:
- the MiniDSP multichannel board (async USB with XMOS reclock) https://www.minidsp.com/products/usb-au ... sbstreamer
- the Pink Faun card http://www.pinkfaun.nl/portal/productaa ... i2s-bridge

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