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Serious talk: No DAC chip, but a FPGA?
Serious talk: No DAC chip, but a FPGA?
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Old 27th October 2016, 07:31 PM   #11
milezone is offline milezone  United States
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Doesn't the FA66 use an AKM4385?
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Old 27th October 2016, 07:35 PM   #12
martin clark is offline martin clark  Europe
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Rob Watts has been doing this over 20yrs; while the Chord Mojo, Hugo and Dave exemplify what is possible now, the work started with his work at Deltec Precicison Audio and everything from the PDM1024 onward.

I have a DPA SX256 amongts other things - still sounds great...
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Old 27th October 2016, 08:17 PM   #13
DPH is online now DPH  United States
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Quote:
Originally Posted by Overkill Audio View Post
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.
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.
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Old 27th October 2016, 08:26 PM   #14
planet10 is offline planet10  Canada
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Serious talk: No DAC chip, but a FPGA?
Quote:
Originally Posted by milezone View Post
Doesn't the FA66 use an AKM4385?
My tech says the FA-66 i have has no DAC chip.

I have pictures of the inside if you want to do a check to see if that is right.

dave
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Old 27th October 2016, 08:33 PM   #15
DPH is online now DPH  United States
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Dave, a look at the chips involved (unless their markings are gone) would go a long ways to closing that loop. (I have no dog in the fight!)
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Old 27th October 2016, 08:51 PM   #16
planet10 is offline planet10  Canada
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Serious talk: No DAC chip, but a FPGA?
This isnt mine, but pictures i found on the web.

dave
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Old 27th October 2016, 08:57 PM   #17
DPH is online now DPH  United States
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There's at least one AKM chip on there (which could easily be the ADC), although I'm having a devil of a time reading much more. Thanks for getting those, Dave.
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Old 27th October 2016, 09:00 PM   #18
planet10 is offline planet10  Canada
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Serious talk: No DAC chip, but a FPGA?
AK4114? A 192/24 digital audio interface transceiver.

I have examined my boards, pulled as many numbers off the interesting chips as i could and looked them up.

dave
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Old 27th October 2016, 09:17 PM   #19
milezone is offline milezone  United States
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I made the assumption regarding the DAC chip based on information from this thread:

https://www.gearslutz.com/board/geek...ps-listed.html

If it's true that the FA66 implements methods alluded to in this discussion then that's very interesting. Either way I'm sure it's a great piece of gear for the price.
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Old 27th October 2016, 09:19 PM   #20
milezone is offline milezone  United States
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The AKM 4385 is the first chip left of the brass standoff in the upper right position.
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