DSP Xover project (part 2)

[gmant123]

Originally Posted by chaparK

I'd like first to briefly mention that the term 'asynchronous' doesn't fit nicely the context of I2S coms. Indeed, I2S is inherently 'synchronous' in the sense that both endpoints use the same clock transmitted along data and synchronously to it.

So this is it: there are 2 endpoints (external DAC and DSP board) but only one clock, so we must decide whether the clock comes from the DSP or from the DAC. We'll call 'Master' the endpoint supplying the clock and we'll call 'Slave' the endpoint sync'ed with the Master's clock.

I said here in a previous post that the expansion port that has 6 extra outs will only work in Master mode. This actually means that data on this port is at the system's central rate, which is derived either from the onboard PLL or from the external clock supplied via the other expansion port (future software revision as discussed above).

You understand now that if you want this port to work in Slave mode (i.e. clock supplied by your DACs), then you're introducing a 3rd clock in the system.
We have to set now who's the 'boss of it all', as would say Lars Von Trier. Do you want the master clock to be generated from the onboard PLL? Do you want that clock to be supplied by the USB receiver? Or do you want the master clock to be supplied by the DACs? This is the question you must answer.

My guess is: just feed your DACs with the system's central clock - which can be either PLL generated or supplied by the receiver. For allowing this, you set your DACs in Slave mode and let the DSP board be the Master of this I2S com.

Thank you Nick!!!, this is a very good ans simple explanation....

As you can see some of us need simply one DSP with digital inputs and outputs without limitation for use with our USB and DACs devices, maybe in the future you can do a simpler product for this purpose...

Regards

Alberto

[dahlberg]

Thanks a lot, most appreciated

[chaparK]

Originally Posted by gmant123

As you can see some of us need simply one DSP with digital inputs and outputs without limitation for use with our USB and DACs devices, maybe in the future you can do a simpler product for this purpose...

Sorry for the complex answer - but Dalhberg has complex questions

The board actually can't be any simpler than it is now.

It does have digital ins and outs so that everything we said above applies only to I2S and is merely optional.
You can indeed simply plug in your equipment and not worry about clocks at all.

Again, sorry if the post above was confusing.

Originally Posted by dahlberg

Thanks a lot, most appreciated

You're welcome

[TNT]

And now we are all very interested in how good the in-built master clock really is? Can we see the sideband spectrum for fs 5hz - 50khz at the DACs, s/pdif and I2S

[Overkill Audio]

Hi Nick,
Your quote " You can indeed simply plug in your equipment and not worry about clocks at all. "
For me this is 100% the problem!
ie Its of great concern to me that there are many ways to connect DSP/ DAC's / USB IO / Clocks together and they all "work" ie produce sound.
But I dont know which is the BEST way to do this...?

What I (and many others?) am seeking is a powerful DSP board with digital in / digital out ( with various USB / I2S / SPDIF / Balanced / optical options ) and the ability to connect our own modules for DAC's / A to D / and power supplies.
I personally would be very grateful if you would please explain in a simple ( laymans terms!) block / flow diagram of your methodology and then maybe a few of the other top digital guys can add their comments?
Thanks in advance
Derek.

[dahlberg]

Quote: What I (and many others?) am seeking is a powerful DSP board with
digital in / digital out ( with various USB / I2S / SPDIF / Balanced / optical options )
and the ability to connect our own modules for DAC's / A to D / and power supplies.



Please don't pester "Chapark" with questions about a whole other idea of how
to make a dsp xo in this thread. There is another one and if he wants to join in
he is of cource most velcome but respect that the man probably has little or no
time to spare these days.

Maybe I'm barking up the wrong tree since you are on a first name basis and
I'm sorry if that's the case

[Ryssen]

Originally Posted by chaparK

Ok. The 5V supply is only used to power digital sections. Some chips use this 5VD as supplied, others require 3.3V and/or 1.2V. The latter are derived from 5VD with onboard regulators.

There's a separate 5VA (analogue). It's derived from the +12V supply. That's why you must always provide +/-12V.

If you plan to use an analogue volume chip, CS3318 needs +/- 8 to 9V and CS3308 needs +/- 5V. These 2 supplies are again derived from +/-12V with onboard regulators.


1A is safe. Power lines are also available on the expansion ports so you can draw current here for your devices attached.

If 1A is the consumption of the 5v line,what is the draw of the +/- 12v line?

[chaparK]

Originally Posted by Ryssen

If 1A is the consumption of the 5v line,what is the draw of the +/- 12v line?

A safe choice is 5V 1A, +12V 1A, -12V 0.3A.

This is more than needed for powering all chips on the board, but it allows you drawing some current from the expansion ports.

Indeed, power lines are available on these ports for easy installation of expansion boards.

[qusp]

I wouldnt assume we wanted to slave the dacs at all, that would actually be the worst choice, to slave the DSP would be much preferred, the clock for the dac outputting sound should have its clock as local as possible, particularly as there is no controlled impedance method to supply clock to anything, or clock buffer/s

[dahlberg]

It does have digital ins and outs so that everything we said above applies only to I2S and is merely optional.
You can indeed simply plug in your equipment and not worry about clocks at all.

And over the spdif outputs the dacs are clocked by the onboard clock and there an is alternative to reclock it or..... ?

From the Buffalo3 se spec

High-precision, ultra-low-phase noise clock and integrated reclocking