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Old 17th December 2007, 11:31 PM   #31
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Ok, I think I'm getting my head around some of it.....

I've set the first SRC4192's output port as master / 256fs giving me a 96KHz output sample rate when using a 24.576MHz reference clock.

The rest of the chips are set with both ports as slave, so they will receive the BCLK and LRCLK signals from the first chip.

So, the master clock on the receiver board WILL have to clock the DAC (or digital amp) section as well as the ASRC chips?

But, does this also mean that the input ports can be slaved, and they don't need a master clock from the LVDS receiver chip (because the ASRC is reclocking everything anyway?)

Also, I've grounded the TDM inputs on all chips - is this correct?

Plus, I'm probably going to add a multiplexer to the receiver board so I can switch between an external input and the amp's own inputs (from it's ADC's / DSPs) - can anyone suggest which type of logic to use for minimal jitter (I don't think it will matter too much though.)


OzOnE.
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Old 18th December 2007, 12:14 AM   #32
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A glaring error I think I'm making is that I assumed the BCLK and LRCLK signals on the output ports were being generated by the ASRC chips themselves.

I'm thinking now that all the chips are slaved from the DAC / Equibit's own master clock, so the BCLK and LRCLK are in fact the "inputs" to the output ports on the ASRCs.

The BCLK and LRCLK signals mainly serve to allow the ASRC to sync the output data to the DAC's clock signals. (I'm probably wrong again here.)

So, your super-duper low jitter Kwak / Tent / Platypus / Tipi clock (only kidding) can still be connected to your DAC, and the ASRC chips will simply sync their data outputs to it.

But, does that mean the reference clock is literally a reference, and is asyncronous to the input and output ports?

OzOnE.

EDIT: BTW, fantastic work Brian! Without this thread I would never have dreamt of trying something like this. I think this type of interface should be made more commonplace sources / amps and should have been standardized way before the advent of HDMI.
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Old 18th December 2007, 09:52 PM   #33
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Quote:
Originally posted by OzOnE_2k3
A glaring error I think I'm making is that I assumed the BCLK and LRCLK signals on the output ports were being generated by the ASRC chips themselves.

I'm thinking now that all the chips are slaved from the DAC / Equibit's own master clock, so the BCLK and LRCLK are in fact the "inputs" to the output ports on the ASRCs.
Correct.
The way I am using them, and the way I would probably recommend for most situations, is for the ASRC to be run as slaves.

Quote:
The BCLK and LRCLK signals mainly serve to allow the ASRC to sync the output data to the DAC's clock signals. (I'm probably wrong again here.)
Actually, you are correct here.

Quote:
So, your super-duper low jitter Kwak / Tent / Platypus / Tipi clock (only kidding) can still be connected to your DAC, and the ASRC chips will simply sync their data outputs to it.
Yes, and an important point here is that the critical low-jitter Master MCLK signal that is feeding the Equibit or DAC IC doesn't even have to go anywhere near the ASRC. This is especially useful if the ASRC is being retrofitted on a separate board.

Quote:
But, does that mean the reference clock is literally a reference, and is asyncronous to the input and output ports?
Correct. IF the ASRC is being used in slave mode, the reference clock is used to initialize the ASRC, and to drive the interface logic and rate ratio estimator circuitry. It isn't directly used to time any of the audio clocks.

(If the ASRC is in master mode, then the reference clock would also be used to generate the audio output clocks, which is why I usually wouldn't want to use it that way.)

Regards,
Brian.
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Old 15th January 2008, 06:39 PM   #34
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I'm still trying to find an HDMI Breakout Box / DAC ...

The new Apple TV device (US$229) only has HDMI, optical audio and RCA output for connection to stereo or multi channel equipment. Since that leaves something to be desired for us "golden ear" types, I would really like to find some way to extract that 24 bit / 192K, dolby 5.1 off of the cable.

Anyone have a suggestion ??
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Old 15th January 2008, 06:48 PM   #35
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