Tír Na HiFi

jkeny wrote:The PCM2706 is not used as a DAC - it is used as a USB receiver for connecting to iPhone, etc
Here's what Rob Watts says

The PCM2706 is just used for the SD USB, it most categorically is not the DAC. The DAC is a pulse array DAC, which uses discrete flip-flops for the analogue OP.

ah thanks for pointing that out John. Now I see that pulse array DAC in the block diagram. Would love to know more about that.
As for the FPGA work involved here, definitely not a weekend job! :-)

jkeny wrote:The PCM2706 is not used as a DAC - it is used as a USB receiver for connecting to iPhone, etc
Here's what Rob Watts says

The PCM2706 is just used for the SD USB, it most categorically is not the DAC. The DAC is a pulse array DAC, which uses discrete flip-flops for the analogue OP.

John,

My bad, you are right.
What chip is then actually used for the pulse array DAC?

Aleg - Chord have programmed their own DAC within the FPGA chip. They are not using an external supplier's DAC. That is the same in my bigger brother Chord DAC64 MkII and IMHO why Chord are different and potentially better DACs for all the reasons that DaveF stated. They have control! But of course they are not cheap.

Jonathan

jrling wrote:Aleg - Chord have programmed their own DAC within the FPGA chip. They are not using an external supplier's DAC. That is the same in my bigger brother Chord DAC64 MkII and IMHO why Chord are different and potentially better DACs for all the reasons that DaveF stated. They have control! But of course they are not cheap.

Jonathan

a house specfic fpga source + pulse array dac with analog ouputs unit might be optimal
but would a fpga source for usb dac's using evaluation boards not be a good step forward?

nige2000 wrote:

jrling wrote:Aleg - Chord have programmed their own DAC within the FPGA chip. They are not using an external supplier's DAC. That is the same in my bigger brother Chord DAC64 MkII and IMHO why Chord are different and potentially better DACs for all the reasons that DaveF stated. They have control! But of course they are not cheap.

Jonathan

a house specfic fpga source + pulse array dac with analog ouputs unit might be optimal
but would a fpga source for usb dac's using evaluation boards not be a good step forward?

I certainly think so. But as DaveF says, that is not a weekend's work. I imagine Chord dcS et al put man years of R&D into the programming of their FPGAs.

I suspect that we should leave it there or start a new thread, as this is not really MQn discussion as such?

Jonathan

jrling wrote:Aleg - Chord have programmed their own DAC within the FPGA chip. They are not using an external supplier's DAC. That is the same in my bigger brother Chord DAC64 MkII and IMHO why Chord are different and potentially better DACs for all the reasons that DaveF stated. They have control! But of course they are not cheap.

Jonathan

Jonathan

If you look at the block diagram ( http://www.phileweb.com/interview/artic ... =221&row=7 ) you can see that the 4E Pulse Array DAC is implemented outside of the Spartan-6 (dashed line around the middel section), so interpreted that as that the actual DA Conversion takes place outside of the FPGA chip.
All the other functions are inside the FPGA, but not the DA-conversion.

Maybe on the detailed picture one can see/follow the low noise reference PSU feeding the DACs.

Cheers

Aleg

Aleg wrote: If you look at the block diagram ( http://www.phileweb.com/interview/artic ... =221&row=7 ) you can see that the 4E Pulse Array DAC is implemented outside of the Spartan-6 (dashed line around the middel section), so interpreted that as that the actual DA Conversion takes place outside of the FPGA chip.

Correct.
You cannot do any digital to analog conversation inside any FPGA. The FPGA here does all the fancy maths on the samples in the digital domain. The external pulse array DAC does the conversion.

Would one of the mods be kind enough to snip this thread from page 430 onwards and put it in a new thread? Lets leave this one for the MQN stuff.
Maybe call the new one DAC's- A Technical Discussion or whatever..

Ta

Done.

I though we were talking about a device that could be controlled to read wav files from a hdd usb nas etc
And have either usb output for usb dacs or have in house d a conversion
Which would be a lot more than just a dac?