Serious talk: No DAC chip, but a FPGA?

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#6
mtoc said:
No DAC chip, but a FPGA, is it possible to achieve groundbreakable level?
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There's little preventing someone more enterprising from baking a lot of the distributed logic of an r-2r DAC (e.g. Soekris's offering) into a single FPGA.

IMO, not worth it. Either put your money and sweat into an existing solution or deep-dive into one of the highest-end audio DAC ASICs and implement it to an inch of its life. (Which would still provide a LOT of intellectual challenge)
 
#7
Here's an interesting video of the designer of what many consider to be the best DAC in the world - the Dave - describing his work: https://www.youtube.com/watch?v=80iu7ifXsOo. The specs are significantly more impressive than any other DAC that I know of.

I don't think the design has anything to do with an R2R dac and to me the technology implemented in the dave - from what I can tell 100+ dsp operations happening simultaneously, is way beyond the capabilities of the top Delta Sigma and R2R chips/discrete available today. I just purchased a Gustard A20H on a whim. In my research and experience with AKM chips, I'm looking forward to hearing it very much. The newly released AKM AK4497 and ESS9038 will render all previous DACs obsolete in my opinion (my opinion). However if funds permitted, I'd skip the likes of MSB, TotalDAC (have extensive experience with Zfoil resistors though and they're amazing), Esoteric (which features the AK4497 in their flagship $20,000 SACD player), and so on, and purchase a Chord Dave. Unfortunately the Hugo is just too barebones and feature limited to justify the cost. Until traction around a DIY project of the sort mentioned in the OP gains some traction, I can only dream.
 
#8
FPGA Vs ASIC Vs OEM Sokeris

DPH said:
There's little preventing someone more enterprising from baking a lot of the distributed logic of an r-2r DAC (e.g. Soekris's offering) into a single FPGA.

IMO, not worth it. Either put your money and sweat into an existing solution or deep-dive into one of the highest-end audio DAC ASICs and implement it to an inch of its life. (Which would still provide a LOT of intellectual challenge)
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Hi DPH,
I am interested in designing (TBO, paying for someone else to design it!) an FPGA solution, but your suggestion of a ASIC solution also sounds like an option...?
I am way out of depth when it comes to the tech talk.....Could you please explain in simple terms the general principals /pro's / cons of FPGA Vs ASIC Vs an OEM vesion of the Sokeris or similar?

Thanks for your time and all the best
Derek.
 
#9
An ASIC DAC and the FPGA as implemented in the Chord seem very different in my understanding. An ASIC dac would = all dacs not including the DAVE and discrete dacs like the TotalDAC. If going this route, I expect the aforementioned AKM and ESS chips to be the best option. http://www.ti.com/lit/an/snaa129/snaa129.pdf

From what I can tell, the Dave implements decimation filtering/sample rate reduction to eliminate aliasing --> waveform 'rebuilt' using a 'waveshaper' which is akin to 'infinite oversampling.'

The pros I see of an FPGA implementation is a significantly more advanced and complex process, compared with a standard DAC chip, all occurring in a single IC, resulting in a much simpler overall design.
 
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#13
Overkill Audio said:
Hi DPH,
I am interested in designing (TBO, paying for someone else to design it!) an FPGA solution, but your suggestion of a ASIC solution also sounds like an option...?
I am way out of depth when it comes to the tech talk.....Could you please explain in simple terms the general principals /pro's / cons of FPGA Vs ASIC Vs an OEM vesion of the Sokeris or similar?

Thanks for your time and all the best
Derek.
Click to expand...

I want to be forthright--we're talking something seriously non-trivial. So to tackle your question thoroughly is beyond my scope here.

Just to get us off on the right foot:
FPGA = field programmable gate array. The breadth of options here are dizzying. But, in short, you'll be looking at something with a large amount of programmable logic with a moderate amount of fixed logical blocks.

It allows one to bake into logic/pipelines algorithms that would otherwise require interpretation by a more general-purpose processor and it's baked-in data pipelines.

ASIC = application specific integrated circuit. This is really a catch-all term for fixed logic circuits. So that's everything from a DAC chip, to a human interface chips in your cell phone, to fixed pipeline audio DSP chips, to gigantic stream processors used in modern workstations/supercomputers.

So in more easily couched terms, with an appropriate FPGA, one could flesh out a DSP pipeline (resampling/noise shaping/etc) and perhaps even a lot of the control logic for a downstream DAC. It's still in the digital domain, however, within the constructs of the FPGA, although that distinction get really blurry really quickly when you're talking about mixed-mode signals.

So if you're really, really, really gung ho about a new DAC topology/implementation, you're going to have to go to a bespoke solution (where you'll need that FPGA), which you'd better *really* know what you're getting into (I don't pretend I do).

If you look hard at the top-end DAC chips available from the likes of AKM/TI/ESS/Cirrus/etc, it makes it hard to say, "I can do a better DAC than them". But implementing one of these chips and squeezing every last drop out of its performance is no child's play either, given the PPB error rates being specified. The analog circuitry, PSU, and layout need to be all there to realize the full benefit of those DACs.
 
#16
This isn’t mine, but pictures i found on the web.

dave
 

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