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Asynchronous I2S FIFO project, an ultimate weapon to fight the jitter
Asynchronous I2S FIFO project, an ultimate weapon to fight the jitter
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Old 17th December 2012, 03:31 AM   #1701
iancanada is offline iancanada  Canada
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Asynchronous I2S FIFO project, an ultimate weapon to fight the jitter
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Originally Posted by qusp View Post
HDMI? not going to happen, licensing rules it out for hobbiest projects.

multichannel? welcome to the line of people poking Ian with a stick
I surrender

I don't think multichannel FIFO gonna be any problem. But I'm still struggling with the DSD mute pattern which will be part of the FPGA logic. Anybody has idea?

Ian
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Old 17th December 2012, 05:08 AM   #1702
qusp is offline qusp  Australia
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Victory!!!

mute pattern to avoid DC offset?
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Old 17th December 2012, 04:41 PM   #1703
fralippo is offline fralippo  Italy
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My new digital source will be based on a high end USB/I2S board followed by a digital filter and PCM1704 dacs. There will be a dual freq. very low jitter clock that will feed everything, synchronously.
Digital filter chosen requires reclocking on outputs and idea is to use simple and well implemented d-type flip-flops.

I'd like to know if the FIFO board might be better than flip-flops solution.

I'm not sure this could be a good idea as the USB board already performs a digital buffering and its I2S output already have a very good quality, with the right clock.

Suggestions and thoughts? Thanks!
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Old 17th December 2012, 04:56 PM   #1704
Fridrik is offline Fridrik
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HI fvale, in theory a fifo integrated directly in the DAC chip and operated with a high precision clock near would be the first method to reduce jitter to mininal, the second best and more pratical method is the design you see described in this thread. Many HI-end DAC integrate some jitter reduction mecanism but to my knowledge they are still not immune to the jitter of the source. So a simple answer would be yes in theory ;-) in pratice I will recevied my FIFO in a few hours and will do a comparaison with some HI-END commercial USB interface.
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Old 17th December 2012, 05:04 PM   #1705
qusp is offline qusp  Australia
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I hope you have good clocks for the fifo in this comparison? without good clock you will not get best results. fifo is all about preparing best conditions to get the best out of your clocks, leaving you with little more jitter than the clock itself+clock buffer

fvale: you cannot feed pcm1704 directly with fifo unless you have the new PCM convertor board, the 1704 requires specialist PCM reclocking, firstly its mono, but it also has other peculiarities.
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Old 17th December 2012, 05:21 PM   #1706
fralippo is offline fralippo  Italy
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Yes, I know that 1704 doesn't accept I2S signals, the PMD200 filter I, and a expert friend of mine, will use has left justified output.
Anyway now we're focused in finding the optimal best methode to reclock digital filter outputs; being a DSP reclocking is not optional, unfortunately
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Old 17th December 2012, 06:16 PM   #1707
qusp is offline qusp  Australia
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Quote:
Originally Posted by fvale View Post
Yes, I know that 1704 doesn't accept I2S signals, the PMD200 filter I, and a expert friend of mine, will use has left justified output.
Anyway now we're focused in finding the optimal best methode to reclock digital filter outputs; being a DSP reclocking is not optional, unfortunately
the PMD200 is completely outgunned by Fifo plus the reclocker I linked above that Ian designed to work with fifo to enable working with various dacs that dont do i2s
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Old 17th December 2012, 11:38 PM   #1708
Adrculda is offline Adrculda  Canada
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Quote:
Originally Posted by qusp View Post
Welcome to the line of people poking Ian with a stick
I think you need a bigger stick :P
__________________
Regards,
Adrian
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Old 18th December 2012, 12:20 AM   #1709
iancanada is offline iancanada  Canada
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Asynchronous I2S FIFO project, an ultimate weapon to fight the jitter
Quote:
Originally Posted by fvale View Post
My new digital source will be based on a high end USB/I2S board followed by a digital filter and PCM1704 dacs. There will be a dual freq. very low jitter clock that will feed everything, synchronously.
Digital filter chosen requires reclocking on outputs and idea is to use simple and well implemented d-type flip-flops.

I'd like to know if the FIFO board might be better than flip-flops solution.

I'm not sure this could be a good idea as the USB board already performs a digital buffering and its I2S output already have a very good quality, with the right clock.

Suggestions and thoughts? Thanks!
Hi fvale,

The goal of a I2S fifo is to isolate the the clock domain from the I2S source and replace it with a better secondary clock. I don't know what high end USB you gonna use? But if the clock from your USB source is good enough then I don't think you need a fifo. So, to use or not to use a fifo is totally up to the clock quality of your i2s source.

Regards,

Ian
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Old 18th December 2012, 05:12 AM   #1710
qusp is offline qusp  Australia
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Quote:
Originally Posted by Adrculda View Post
I think you need a bigger stick :P
no, a small stick is fine, i'm only politely (but reasonably regularly) poking with the stick, because I know that my (and your) agenda isnt really Ian's agenda, since at least for now hes 2 channel only.

I didnt mention it, but either your skimming is not very good, or you didnt really skim the whole thread, its been mentioned many times, not just by me.
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