FPGA DACs

[diecaster]

The OP should clarify, but I don't believe he wanted a list of DACs that included FPGA chips. 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.

[diecaster]

24 minutes ago, Em2016 said:

 

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

 

Okay, you are being unnecessarily pedantic.

[diecaster]

All I know is that Ted Smith has done some incredible things with FPGA technology used in the PS Audio DirectStream DAC. In essence, each upgrade is a whole new DAC!

[diecaster]

12 minutes ago, barrows said:

I do not think that is the case at all.  As noted, the FPGA does not do D to A conversion in these DACs (PS Audio, Chord, etc).  Generally speaking, the FPGA does signal processing up to very high data rates, and then outputs that to some kind of D to A conversion stage, generally discrete, and fairly simple considering the super high rate it is fed, but there is no analog output for the FPGA.

 

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.

[diecaster]

My point is that there are lots of things I could be correcting people on in minute details that make no difference to the conversations taking place. It would be pedantic to do so.

 

The simple fact is that DACs that do not use single IC DAC chips to do D to A conversions have multiple electrical circuits designed to do the same thing. In other words, what the FPGA does would be one or more sections inside the single DAC chip. So, while the FPGA does not do analog, the circuit it is part of does. Heck, most of the circuits inside a DAC chip don't do analog....

[diecaster]

@Em2016

 

Quite true what Rob says. PC's are not real time devices. DACs pretty much have to be.

[diecaster]

Well, I find that my DirectStream with Snowmass sounds better using HQPe to upsample, filter, and noise shape to 352.8 than by letting the DirectStream do it. The built-in upsampling is much better than it was in Redcloud but still not better than HQPe.