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Old 28th September 2012, 01:21 PM   #11
vzs is offline vzs  Europe
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I'm a skeptical person so I think ideal approaches don't exist.
Point me to an off the shelf FPGA/DSP DF board __not complete DAC product__ which implements these apodizing or minimum phase filters and will be happy to try it. So compared to off the shelf DFs this approach might be better - will see.
Agree that 384k would be better but with SPDIF I'm tied to 192k and a fifth-sixth order LPF on the analog side.
I'm crossing my fingers that KOON3876 will make the 25$ Raspberry Pi stream 192k and who knows, 384k too. For that price that can be a game changer digital source.

LE: don't care either where the pure math happens until I get a clean stream to my DAC

Last edited by vzs; 28th September 2012 at 01:40 PM.
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Old 28th September 2012, 01:55 PM   #12
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hmm what makes you think fpga is any less mumbo jumbo than a software implementation of the same thing?
The fpga is a much more controlled environment. It's just a piece of hardware, and once you set it right, you will never experience issues and differences related to operating systems, running processes, drivers, playback software and so on. Plus, the fpga inherent parallellism makes them quite suitable for the task. Just my 2 cents.
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Old 28th September 2012, 02:20 PM   #13
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Originally Posted by vzs View Post
I'm a skeptical person so I think ideal approaches don't exist.
Point me to an off the shelf FPGA/DSP DF board __not complete DAC product__ which implements these apodizing or minimum phase filters and will be happy to try it. So compared to off the shelf DFs this approach might be better - will see.
Agree that 384k would be better but with SPDIF I'm tied to 192k and a fifth-sixth order LPF on the analog side.
Of course , nothing is ideal, we were talking about alternatives.
A far as I remember Anagram was offering something like that in the past.
Maybe we should start such a DF board that will do minimum phase, apodising or whatever type of filter - it's been too much time since we are the prisoners of some off-the-shelf chips.
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Old 28th September 2012, 02:47 PM   #14
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...Maybe we should start such a DF board that will do minimum phase, apodising or whatever type of filter - it's been too much time since we are the prisoners of some off-the-shelf chips.
I cannot agree more... it's a very good idea
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Old 28th September 2012, 03:43 PM   #15
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Sounds fun... you can count on me on this one. However let's not hijack Ian's thread. Maybe open a new one.
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Old 29th September 2012, 01:00 PM   #16
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The FPGA architecture is much suitable for implementing the hardware based digital filter though the software based DF is more flexible. To develop a soft one, e.g for foobar2000, you need to develop a plugin, but for a fpag design, the R&D task would be more focus on the DF itself.

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Old 29th September 2012, 01:41 PM   #17
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now you just need to maintain Ians interest and there'll be a board design ready for prototype within the month =)
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Old 29th September 2012, 01:45 PM   #18
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You guys are really getting it. I am I agree with your as*sment fully, thankyou for your support on this. We are talking about an new way to look at a DAC. Let's face it if it weren't for PC's we wouldn't even be talking about DAC's 15 years after they basically went exinct (or Ian's FIFO.)

And yes the argument of pure math, hardware vs a PC (toy) doing the math is an issue. But an FPGA isn't the answer unless you reclock after words and then we might as well start over the whole project. I don't run any process off a PC at work, there is a move toward doing that, however I won't go there yet.

But since this is about music I am more open minded toward the usefullness of the convenience to put together filter algorthms from the PC which can compete with the handful of experts who actually pull of decent oversampling code. The PC can help the creative side of things because it isn't pigeon holed to a small group who know AD Sharc/Blackfin or others.

So what we have presented is an NOS DAC if you want, but this is step in a direction for the potential to evolve the DAC as a further integration to the PC.

The best part is it allows the hobbiest to build the DAC whith the chip one wishes and focus on what we diyaudio freaks are good at - the analog section.

Ian, Thankyou for presenting this.
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Old 29th September 2012, 01:52 PM   #19
qusp is offline qusp  Australia
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Originally Posted by Lupulroz View Post
The fpga is a much more controlled environment. It's just a piece of hardware, and once you set it right, you will never experience issues and differences related to operating systems, running processes, drivers, playback software and so on. Plus, the fpga inherent parallellism makes them quite suitable for the task. Just my 2 cents.
hmm I guess I havent had as many troubles, as I see it the PC has more than enough processing power, is more flexible and allows the crossover, volume control and OSF to be part of one and the same process. hardware is nice and I understand what you mean, but the issues you speak of are with certain software designers and the users susceptibility to black magic claims, nothing to do with the PC/MAC itself.

write the code to utilize the vector processor in the i5/7 or a suitable graphics card

Last edited by qusp; 29th September 2012 at 01:56 PM.
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Old 30th September 2012, 06:09 AM   #20
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