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Old 2nd September 2011, 03:45 AM   #1
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Default Open Source DSP XOs

Some interest was expressed on the nCore thread about implementing a digital version of the Orion ASP. Since its no longer relevant to that thread, here's a new one to see if there's any interest in a team effort to implement open source DSP crossovers. Not specifically restricted to SL's ASP but that might be a great starting point if the analog version's details were available with SL's permission.

My initial (crazy?) idea is to get models of various XO components working in LTSpice using Kendall Castor-Perry's delay line implementation here:

Which filters are noisier – analog or digital? part 2
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Old 2nd September 2011, 09:26 AM   #2
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I'd be interested. As in the general idea of open-source DSP, and the Orion would be a great initial case.

So. Team-building: We need engineers with DSP experience, or equivalent I'm not one, but I am a computer scientist so I can help with programming stuff. Can't commit lots of time as I'm knee deep in paid work, but I'll advise as best I can!
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Old 2nd September 2011, 10:59 PM   #3
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OPen source audio dsp for filters sounds wonderful. are you thinking diy all the way like using fpga or some already available dsp core? If fpga is way to go skip spice go for math software.
More or less i thing first to do is implement general signal path so we can use multiple filters without caring what inter connect we are using is benefiting most and hopefully people can easily try ne w filters.

REALLY WHAT KIND OF PLATFORM?

most of times when i am talking digital technology i get flamed, IT IS NOT MY FOUL THAT THEY DON*T UNDERSTAND WHAT I AM SAYING. I am not american and my english is poor. if that isn't enought to confuse you I AM DRUNK.
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Old 3rd September 2011, 02:19 AM   #4
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Originally Posted by fzaad View Post
OPen source audio dsp for filters sounds wonderful. are you thinking diy all the way like using fpga or some already available dsp core? If fpga is way to go skip spice go for math software.
I was thinking to keep it relatively platform independent by doing the design more conceptually using LTSpice. But it can't be entirely platform independent so ARM was what I had in mind - at the least that's vendor independent. ARM means 32bit fixed point processing (with the option for 64bit math if/when called for).

FPGA is a bit daunting for any DIYer who's not got experience with it (which is probably most). However there's a growing number of free or low cost tools when it comes to ARM and its a micro which happens to run fast enough to handle DSP.
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Old 3rd September 2011, 02:45 AM   #5
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This is getting over my head I'm out ...
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Old 3rd September 2011, 02:48 AM   #6
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Originally Posted by kristleifur View Post
This is getting over my head
You're a computer scientist right? So what's baffling you here?
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Old 3rd September 2011, 11:47 AM   #7
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Quote:
Originally Posted by kristleifur View Post
This is getting over my head I'm out ...
If arm is way to go. we can program it with C.
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Old 3rd September 2011, 12:13 PM   #8
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Quote:
Originally Posted by abraxalito View Post
I was thinking to keep it relatively platform inspice dependent by doing the design more conceptually using LTSpice.
When LTSpice is good tool i think since we are doing actual coding it is better to do with math. Math is cross platform. when using math soft we can test actual code more effectively. When it comes to resolution my experience we need minimum 56 bit in fixed point.

Have you looked Home :: OpenCores they have openrisc that sounds promising. when you said open source have you looked GNU arm tools?
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Old 4th September 2011, 02:13 AM   #9
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Interesting idea. Source code availability aside, what processing capabilities are needed which aren't already available from existing solutions (MiniDSP, SigmaDSP, VSTs such as Frequency Allocator or ReaEQ, rackmount platforms like the ones from Ashley and Behringher, or even Hypex's DLCP if they ever get around to shipping it)? Replicating the ASP in any of these tools is just a matter of a couple minutes' data entry from Linkwitz's block diagram.
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Old 4th September 2011, 02:29 AM   #10
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Quote:
Originally Posted by fzaad View Post
When LTSpice is good tool i think since we are doing actual coding it is better to do with math.
Do you mean Mathcad? Or Matlab? How to implement math?

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Math is cross platform. when using math soft we can test actual code more effectively.
Mathsoft? Is that a free package?

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When it comes to resolution my experience we need minimum 56 bit in fixed point.
Doesn't that depend on what filter is being run though? For example the link I gave shows that for LF filters, more resolution is needed than with HF, given the same amount of noise.

Quote:
Have you looked Home :: OpenCores they have openrisc that sounds promising. when you said open source have you looked GNU arm tools?
I looked but its relevance here escaped me. Care to elucidate? I have looked at GNU ARM tools, haven't played.
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