FPGA DACs

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Ayre? A combination of ESS chip and FPGA for Ayre's own filters?

 

[asdf1000]

35 minutes ago, diecaster said:

instead used one or more FPGA to handle the D to A conversion.

 

Is it the FPGA itself that is converting D to A? In particular the A.

 

Is there a separate analogue output stage in Mojo or is that derived directly from the FPGA?

Absolutely. An FPGA is entirely digital and cannot have analogue outputs. This is done with discrete components (flip flops, resistors, capacitors and separate reference circuitry). Doing the analogue discretely has big benefits. In designing silicon DACs there are enormous problems - the clock has to be distributed, and this increases jitter, the substrate injects noise and distortion into the analogue parts, the reference circuitry can't have low enough impedance and is noisy, resistors are non-linear, capacitors are non-linear too. None of these problems apply with discrete DACs.

 

http://www.the-ear.net/how-to/rob-watts-chord-mojo-tech

[asdf1000]

10 minutes ago, diecaster said:

 

Okay, you are being unnecessarily pedantic.

 

Just sharing accurate info from a DAC designer, for learning (myself included) purposes.

[asdf1000]

30 minutes ago, diecaster said:

 

You are welcome to your opinion....but in regards to what the OP was requesting, it matters not that the FPGA doesn't actually do the D to A conversion completely on it's own. Without the FPGA the conversion could not happen. It's essentially part of a multi-chip D to A converter instead of being a single chip converter.

 

Your statement was "I think he wanted a list of DACs that did not have traditional DAC chips and instead used one or more FPGA to handle the D to A conversion."

 

I shared the quote from Rob Watts to clarify this point in bold. Barrows just doing the same.

 

Many people out there seem to think (myself included at one point) it's the FPGA doing the D to A conversion. This was just clarification, nothing more.

 

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2 hours ago, jabbr said:

The FPGAs in common use in DACs just don't have anywhere close to the horsepower of the common CPUs used in PCs. CPUs are very highly optimized and relatively cost effective, and in particular when married to a GPU, the performance just isn't there.

 

I know you've said the above is about FPGA in common use in DAC's, which means there are exceptions and this is probably one, from Rob Watts:

 

"All competent DAC's up-sample and filter internally; the issue is how well that filtering is done, in terms of how well the timing of transients is reconstructed from the original analogue. Computers are poor devices to use for manipulating data in real time as they are concurrent serial devices  - everything has to go through one to 8 processors in sequence. With hardware and FPGA's you do not need to do that, you can do thousands of operations in parallel. Dave has 166 DSP cores with each core being able to do one FIR tap in one clock cycle. That is incredibly powerful processing power way more powerful than a PC."

 

https://www.head-fi.org/threads/chord-electronics-dave.766517/page-193#post-12568029

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4 hours ago, Miska said:

Chord is SDM DAC...

 

Yup, 5 bit delta sigma...

 

https://www.head-fi.org/threads/hugo-tt-2-by-chord-electronics-the-official-thread.879425/page-142#post-14557160

 

https://www.head-fi.org/threads/watts-up.800264/page-34#post-13934433