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Opus DAC with Raspberry Pi Type B
Opus DAC with Raspberry Pi Type B
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Old 18th March 2015, 07:17 AM   #1
kinku is offline kinku  United States
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Default Opus DAC with Raspberry Pi Type B

Hi,
I am wondering if anyone has experience with using Raspberry pi Model B's I2S output feeding Twisted pear audio opus DAC ?
If anyone has experience with it please guide me.

Last edited by kinku; 19th March 2015 at 04:25 PM.
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Old 19th March 2015, 05:26 AM   #2
Dr Jim is offline Dr Jim  United States
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I can't speak to how well the Raspberry Pi B will talk to a Twisted Pear Opus - but can say with some assurance that the I2S on the 'B' model seems to be quite clean and does not appear to throw off many of the artifacts that the original Pi suffered from.

Using both an original Pi and a Pi 'B' to drive a HiFiDigi I2S -> S/PDIF adapter feeding a PCM1794 OEM eval board driving a class A headphone amp into Fostex T20 modded phones I noted that passages which seemed congested and unclear through the Pi 'A' now played as I believe they were meant to be heard on the 'B.'

Specifically some of the moments in Mahler's 1st and 5th symphonies where the brasses blare out over the first & second strings now seem 'right' - the horns have body, and an almost 'silvery' note without being harsh, while the strings remain quite distinct both tonally and in their correct places.

There's no doubt that there is more CPU horsepower in the 'B,' there also seems to be better noise rejection, and far less cross-talk between the network and the I2S buses - with the net result that low-level passages emerge from a completely 'black' sonic background with out any sense of pre-echo, odd - almost dithered - background hiss, or an 'edge-of-hearing' ringing that the Pi 'A' would sometimes throw off.

For about $75 USD, the Pi 'B' + HiFiDigi board combo seems to be a surprisingly competent network music streamer - so the Pi B should drive the Opus DAC well if due care is used the transporting the I2S signal.

Cheers

Jim
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Old 19th March 2015, 01:07 PM   #3
kinku is offline kinku  United States
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Thanks Jim. I have missed the digital age and don't know much about the i2s connections to DAC chips. Is there any cheat-sheets or articles that would explan the i2s connection between devices?
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Old 19th March 2015, 01:54 PM   #4
Redshift187 is offline Redshift187  Canada
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I think you might be mixing up Pi models. A and B were both original, B had ethernet and more RAM.

Model B 1.0: no I2S (not all the proper GPIO pins were broken out to headers)
Model B 2.0: I2S
Model B+ 1.0: More USB ports, micro SD, rounded corners
Pi 2 model B: Faster CPU, more RAM

Unfortunately, I have a B 1.0, so I can't hook mine up to a DAC
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Old 19th March 2015, 04:25 PM   #5
kinku is offline kinku  United States
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To be clear we are discussing on Pi Model B Revision 2.0 512MB
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Old 19th March 2015, 04:30 PM   #6
kinku is offline kinku  United States
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AMB labs gamma 2 is also a strong candidate.Anyone did comparison with Oppus vs Gamma 2 in technical aspects. I am reading Twisted Pear site but don't think there are not many details for a novice like me.
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Old 19th March 2015, 07:22 PM   #7
glt is offline glt  United States
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May not work with Opus as the dac chip needs a master clock and the RPi does not have an external master clock.

Don't know if the dac can lock to the bit clock
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Old 19th March 2015, 07:26 PM   #8
kinku is offline kinku  United States
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So how about AMB gamma 2? I guess it has a master clock on board. But trying to find out more about the over sampling to 96KHz . Is it going to down sample the 192kHz material?
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Old 11th April 2015, 12:11 AM   #9
funkz is offline funkz  Australia
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Quote:
Originally Posted by glt View Post
May not work with Opus as the dac chip needs a master clock and the RPi does not have an external master clock.

Don't know if the dac can lock to the bit clock
Haven't looked into the DAC side, but people have BCK and MCK going on the RPi end.

https://www.raspberrypi.org/forums/v...hp?f=44&t=8496


I'm considering a combination of RPi 2.0 + Opus also, starting to look into it. Will be interested to hear how the I2S interfacing goes for others.
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