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Old 9th September 2008, 04:13 AM   #21
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Join Date: Oct 2001
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Quote:
Originally posted by Johnix

I still think that tweaking an AVR is the best option for that specific application because the universal player can't perform :
- 7.1 channels
- 2.0 to 5.1 matrix
- volume control
- source selection
etc...
So, in short, you buy an 8ch receiver, ignore the onboard 8ch power amp principally to get faux 5.1 ? Might as well buy a MC12 and be done with it.
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Old 9th September 2008, 06:59 PM   #22
Johnix is offline Johnix  France
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Quote:
and we still have to debate, what is the best path??

i am seriously worried about the excessive jitter
from all the conversions and spdif chips ...

do you believe it will be an issue ?

how long of cable can we safely run I2S lines on before getting some signal distortion ? [/B]
First, you have to investigate on the DCX2496 spdif input side. I doubt is uses top grade components and it may be of some interest to mod this DCX2496 (clocks, psu etc...)

Now if you'd like to mod and AVR to add 4 spdif outputs, there will be absolutely no digital loss during this IS=>SPDIF conversion ; the master clock used should be the same that the one feeding the DACs thus the quality of conversion is not dependant on the chips used but on the clocks inside the AVR. High-end AVRs shouldn't be too weak on that parameter.

The length of the cable should be approx 10 to 20 centimeters (sorry guys, I don't speak your inch language...). With proper grounding, this will perfectly carry audio signals sampled at 48kHz.
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Old 10th September 2008, 02:42 AM   #23
JinMTVT is offline JinMTVT  Canada
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Quote:
Originally posted by rfbrw


So, in short, you buy an 8ch receiver, ignore the onboard 8ch power amp principally to get faux 5.1 ? Might as well buy a MC12 and be done with it.

from lexicon's page :

For maximum flexibility, each of the main audio outputs has independent crossover, speaker distance, and output level controls. The crossovers can be adjusted in 10Hz increments from 30 to 120Hz. The MC-12 HD is also THX Ultra2-certified and integrates the processing and enhancements of the THX Ultra2 standard.


WOW ..what an impressive feature!
xovers adjustable in 10hz from 30 to 120hz...
exactly what i am looking for ..

NOT
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Old 10th September 2008, 02:47 AM   #24
JinMTVT is offline JinMTVT  Canada
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Quote:
Originally posted by Johnix


First, you have to investigate on the DCX2496 spdif input side. I doubt is uses top grade components and it may be of some interest to mod this DCX2496 (clocks, psu etc...)

Now if you'd like to mod and AVR to add 4 spdif outputs, there will be absolutely no digital loss during this IS=>SPDIF conversion ; the master clock used should be the same that the one feeding the DACs thus the quality of conversion is not dependant on the chips used but on the clocks inside the AVR. High-end AVRs shouldn't be too weak on that parameter.

The length of the cable should be approx 10 to 20 centimeters (sorry guys, I don't speak your inch language...). With proper grounding, this will perfectly carry audio signals sampled at 48kHz.

i read that the clock signal is compressed within the SPDIF signal and not with the I2S, so any conversion between the 2 introduces some jitter
not too sure on how much though..wasn't mentionned

so do you believe that sending out spdif signals would do it ?

don't know if i'll have much time to mod every single dcx input ..i'll probably have to mod already all the outputs to get better DACs in there
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Old 10th September 2008, 03:03 PM   #25
gmarsh is offline gmarsh  Canada
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If you want to roll your own DD/DTS decoder, both are open standards since they're used for terrestrial TV broadcast. DTS is an ETSI standard, and Dolby Digital is the audio component of ATSC, known there as "A/52".

DTS: Go to this site - http://pda.etsi.org/pda/queryform.asp - search for "DTS Coherent Acoustics". What you'll want is ETSI TS 102 114 V1.2.1 (2002-12), you'll have to register (free) on the site to get it.

Dolby Digital: http://www.atsc.org/standards/a_52b.pdf

There are also software libraries for decoding these two, "libdca" for DTS and "liba52" for DD, that you can use as a software reference.

Now, these won't cover Dolby Digital Plus, Dolby TrueHD, or any of the new DTS Neo:whatever modes. Also, if you actually implement and sell a system based on these specifications, you'll need a license from Dolby or DTS.

As far as hardware to run this stuff on, this could be anything from a DSP chip on a custom board to a off-the-shelf PC with a multichannel soundcard. That all depends on your capabilities.
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Old 10th September 2008, 05:41 PM   #26
Johnix is offline Johnix  France
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Quote:
Originally posted by JinMTVT



i read that the clock signal is compressed within the SPDIF signal and not with the I2S, so any conversion between the 2 introduces some jitter
not too sure on how much though..wasn't mentionned

so do you believe that sending out spdif signals would do it ?

don't know if i'll have much time to mod every single dcx input ..i'll probably have to mod already all the outputs to get better DACs in there
the SPDIF DIT chip is simply a IS to biphase encoder, adding preamble and various other bits but is synchronous to the global clock of the AVR. So if you have (significant) jitter before conversion, you'll have also (significant) amount of jitter after. But if you feed proper clock to your DIT stage, forget about jitter.

I agree on the point that changing the (cheap) DACs on your DCX will greatly improve the whole thing
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Old 10th September 2008, 07:34 PM   #27
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Quote:
Originally posted by Johnix

....... changing the (cheap) DACs on your DCX will greatly improve the whole thing
But not beyond the limits imposed by the CS8420 at the input.
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Old 11th September 2008, 12:15 AM   #28
JinMTVT is offline JinMTVT  Canada
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Quote:
Originally posted by rfbrw


But not beyond the limits imposed by the CS8420 at the input.

info on this can be found on the DCX thread ???


John : great !!!

so i will be looking for the correct AVR in the coming months , and then i'll open it up and post it in here!

i hope that you will be of assistance, again
as you have prooved very helpfull mon ami

thanks


GMarsh : i do not wish to go at that extent ..
i do not posess the required skills/knowledge
for software/chip standalone,
unless a kit or something similar to diy kits is available.

i'd rather mod a commercial , working AVR to get all the features at the same time, than invent something that will take very long time to complete and will not provide me with all what i need.

and then the recent avr will support all those other multichannel signals and more
+ video switching and balbalbal ..
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Old 11th September 2008, 11:26 AM   #29
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Quote:
Originally posted by JinMTVT

info on this can be found on the DCX thread ???

Not quite.
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Old 11th September 2008, 05:21 PM   #30
Johnix is offline Johnix  France
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Quote:
Originally posted by rfbrw


But not beyond the limits imposed by the CS8420 at the input.
I totally agree.

Anyway Cirrus Logic is definitely a bad choice for SPDIF related tasks.
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