Hi all,
I am a little bit lost,
Are new drivers to have DAC+ PRO in master mode available?
It should sound better
If yes is there any measurements vs DAC+ standard version ?
Regards,
Christian
Date
Votes
15 comments
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HiFiBerry team Hi Christian,
in standard measurements (% THD, frequency response), both cards behave almost identical. The impact of jitter on DACs is discussed controversially. You usually don't see the impact in THD measurements. Some people might not hear a difference between both cards, other might hear a difference.
Best regards
Daniel -
HiFiBerry team I forgot: The new drivers are available for quite some time now. They are integrated in the standard 4.1 Raspberry Pi kernel.
Best regards
Daniel -
Christian Votava Hi Daniel,
thanks for answer,
If my understanding is correct, in master mode, playing music in CD quality (44.1khz) is not well managed with RPI in slave mode as the internal clock is 19.2 mhz. It can play well at 192khz, 96khz, 48khz but it is harder to play 44.1khz.
So, for all DAC except the DAC+ PRO the music should be 'distorded' or re-sampled at another frequency (ex 48khz) ???? Or is there an adaptative code in the driver to change the frequency in real time to 'emulate' 44.1khz???
The DAC+ PRO can work in master mode and has an internal clock100% compatible with the CD quality (44.1 khz). should it be better ???
What can be the impacts on sound quality ?
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HiFiBerry team Hi,
even with the DAC+ the music isn't resampled at 44.1kHz. The Raspberry Pi can also create clocks for this sample rate. The only problem is that there is a lot of jitter on the clock signal. As most of the jitter is being removed by the PLL of the DAC+, you don't see a difference in measurements.
Some people might still notice a difference, other might not hear a difference.
Best regards
Daniel -
Christian Votava Hi Daniel,
Usually, divider speed is an integer on microprocessors and 44.1khz is not a multiple of 19.2mhz. There is an article below that may be confirm what I wrote.
Maybe the jitter comes from this point?
http://www.dimdim.gr/2014/12/the-rasberry-pi-audio-out-through-i2s/
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HiFiBerry team Yes, that's were the jitter comes from. The Raspberry Pi has different method for clock generation and if the divider is not an integer divider you will have higher jitter figures.
Best regards
Daniel -
HiFiBerry team Note that not everything written in the article you linked is correct. Jitter has nothing to do with "bit-perfect".
Best regards
Daniel -
Christian Votava definitely agree. For sure Rasperry is bit perfect lol. If it wasn't bit perfect, the outpout data may brake the speakers... Or your ears.
Anyway, thank you Daniel for the details you provided
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vma I am not sure, but it looks that only Hifiberry Dac+ Pro has correct clocking. Other manufactures have the same problem with not exact clock. Am I correct?
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HiFiBerry team I can't and won't discuss features of boards not designed by us.
Best regards
Daniel -
vma Ok, thank you.
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Christian Votava @vma: you are correct. I think there is no other DAC @ I2S working as master. As Raspberry can not work at 44Khz precisely it means more jitter. But unfortunately there are no measurements available to know the gap.
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Peter The DAC+ Pro may be the only board with its own onboard clock generator but I don't think its the only one with the "correct" 44.1KHz clock. The product description states that the clock is derived from a P{LL (phase locked loop).
After the PLL, and especially at the output of the board, jitter is not going to be easily measurable without a really good spectrum analyzer - or audible, which is probably why nobody has done it.
Jitter was a much bigger problem in inexpensive DACs 5 or ten years ago than today.
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vma I am not a "HiFi" expert, but I think that jitter is still a problem. I am going to order DAC+ Pro, because it has onboard clock generator - I have not seen it somewhere else. It is pity that there are no "serious" reviews or measuring of the Raspberry DACs. Perhaps it is not as good business as with expensive DACs.
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Christian Votava Peter,
I never said DAC+ PRO is the only one with its own clock generator. I said "I think there is no other DAC @ I2S working as master" ... For the Raspberry of course.
Saying that, it should reduce the jitter, but there are no measurements.
vma: there are some measurements between RASPBERRRY I2SDAC, CD player, and USB DAC on the web..... and a good thread in a forum about it. The jitter is very important on raspberry pi with I2S DAC in slave mode. Don't know in master mode.
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