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Old 27th October 2016, 11:55 PM   #31
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Had to happen sometime!
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Old 28th October 2016, 12:44 AM   #32
soekris is offline soekris  Denmark
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It's all about the right tool for the job, and then limiting using too many different tools for a design....

FPGA's are great for bit processing and fixed filter functions, perfect for a DAC like the dam1021. But if you want to implement more complex processing, like a crossover, use a DSP as they much cheaper than a large FPGA.
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Old 28th October 2016, 01:22 AM   #33
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Agreed. The simplicity factor is what makes such a design so appealing. Start adding too much and things get weird and bloated. Soren, I own a 1021 which is up for sale currently. I simply don't have time/confidence to dedicate to completing it even though it's 90% there. It's a design I'd like to come back to at some point. Alternatively, I hope you continue exploring this realm as your work is really a gift to the community.
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Old 9th January 2017, 09:36 AM   #34
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Default Ring dac

Sorry but first FPGA DAC is (was) the Arcam/DCS ring dac.
It is a very interesting concept of error distribution. You can find in this forum info about it.
Anyway using FPGA is only a smart way to save money...
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Old 10th January 2017, 10:00 PM   #35
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Originally Posted by mtoc View Post
No DAC chip, but a FPGA, is it possible to achieve groundbreakable level?
Commercial DAC chip converter versus an FPGA based converter mostly boils down to a choice between converter linearity versus converter quantization noise. An digital FPGA based converter will necessarily be 1-bit. Which means that it can natively produce only two quantization levels. As such, 1-bit converters produce a great deal of quantization noise. Sigma-delta modulation is a DSP technique which can greatly reduce the in-band quantization noise by relocating it out of band. What 1-bit converters offer is perfect integral linearity, as two points can only define a perfectly straight line. 1-bit converters, of course, are nothing new.

Native multibit DAC chips feature more than two quantization levels. To be multibit, such converters need 2 or more bits of native resolution. The more native bits, the less can be the quantization noise. However, having more than two levels means it's possible for non-linearity to result. What multi-level converters offer is a greatly reduced quantization noise. Most audio DAC chips today combine multiple levels with sigma-delta modulation, in an attempt to realize the best of both worlds.

There seems to be two motivations for FPGA based 1-bit converters. The first reason is that FPGAs enable a massively parallel 1-bit converter implementation. Very basically, many 1-bit converters output the same bitstream slightly time skewed from each other. The other reason, I suspect, is that the inclusion of an FPGA has become a marketing bullet with audio consumers. Consumers are constantly looking out for who may have the secret technical sauce to delivering musical satisfaction. FPGAs are the latest ingredient in that technical sauce for some designers.
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Last edited by Ken Newton; 10th January 2017 at 10:30 PM.
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Old 11th January 2017, 12:51 PM   #36
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Originally Posted by mgiammarco View Post
Sorry but first FPGA DAC is (was) the Arcam/DCS ring dac.
.....
Deltec was around before the ringdac

Last edited by rfbrw; 11th January 2017 at 12:55 PM.
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Old 11th January 2017, 01:36 PM   #37
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Quote:
Originally Posted by Ken Newton View Post
Commercial DAC chip converter versus an FPGA based converter mostly boils down to a choice between converter linearity versus converter quantization noise. An digital FPGA based converter will necessarily be 1-bit. Which means that it can natively produce only two quantization levels. As such, 1-bit converters produce a great deal of quantization noise. Sigma-delta modulation is a DSP technique which can greatly reduce the in-band quantization noise by relocating it out of band. What 1-bit converters offer is perfect integral linearity, as two points can only define a perfectly straight line. 1-bit converters, of course, are nothing new.

Native multibit DAC chips feature more than two quantization levels. To be multibit, such converters need 2 or more bits of native resolution. The more native bits, the less can be the quantization noise. However, having more than two levels means it's possible for non-linearity to result. What multi-level converters offer is a greatly reduced quantization noise. Most audio DAC chips today combine multiple levels with sigma-delta modulation, in an attempt to realize the best of both worlds.

There seems to be two motivations for FPGA based 1-bit converters. The first reason is that FPGAs enable a massively parallel 1-bit converter implementation. Very basically, many 1-bit converters output the same bitstream slightly time skewed from each other. The other reason, I suspect, is that the inclusion of an FPGA has become a marketing bullet with audio consumers. Consumers are constantly looking out for who may have the secret technical sauce to delivering musical satisfaction. FPGAs are the latest ingredient in that technical sauce for some designers.
Great summary. Thanks Ken.
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Old 11th January 2017, 10:33 PM   #38
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Originally Posted by Ken Newton View Post
The first reason is that FPGAs enable a massively parallel 1-bit converter implementation. Very basically, many 1-bit converters output the same bitstream slightly time skewed from each other. The other reason, I suspect, is that the inclusion of an FPGA has become a marketing bullet with audio consumers. Consumers are constantly looking out for who may have the secret technical sauce to delivering musical satisfaction. FPGAs are the latest ingredient in that technical sauce for some designers.
I agree too.
Basically ring dac uses many 1-bit converters in a random way to distribute noise and to decorellate it from input signal.
Then using an fpga is economically more convenient because usually:

1) you have a great idea for a new tipe of dac
2) you simulate in your lab on a fpga
3) you build a custom chip and mass produce it

On point 3) because hi-end producers build few pieces it is not conveniente to build a custom chip so (incredibly) it becames more convenient to put the fpga directly on final board. Then marketing department tells that fpga "is the best"
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Old 11th January 2017, 11:41 PM   #39
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Originally Posted by mgiammarco View Post
...On point 3) because hi-end producers build few pieces it is not conveniente to build a custom chip so (incredibly) it becames more convenient to put the fpga directly on final board. Then marketing department tells that fpga "is the best"
The issue driving FPGA use in production is much more economic than it is convenient. The problem with an custom ASIC is it's multi-million dollar fixed cost (wafer mask sets, etc). FPGA doesn't entail those huge fixed costs, however, it does entail a higher per unit cost. The deciding factor is the expected total production unit volume. At some high unit volume, the per unit cost savings of an ASIC justify it's higher fixed cost. Which is why, as you indicated, smaller volume products utilize FPGA. As far as product marketing departments are concerned, having their own custom ASIC in their product carries more market cache than having an FPGA. The huge fixed cost difference for low volume products simply overrides any such marketing luxury.
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Old 12th January 2017, 12:01 AM   #40
Bigun is offline Bigun  Canada
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How about an FPGA to convert the data stream into DSD ?

It's a kind of DAC when you think about it.
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