NPC filter
Please do try it and report your findings for every ones benefit. Be sure to review the thread, there are many hints on how to wire it up.
I spent some time reverse engineering the SAA7220 - it uses 12bit coefficients, just like the DS says (12*16 multiplier).
Perhaps your reconstruction filter isn't up to snuff? I certainly had that problem (lack of HF clarity) before I built a sharp filter to take out the images - now my HF is as sweet as I need
I'll probably be revisiting my digital filter project sometime later this year, using a new LPC5411x chip from NXP which has the interfaces required along with enough MIPs.... I reckon for digital filters, minimum oversampling is best, 4X seems too high.Nice if someone would emulate the PMD100....
<edit> Looking at the FR plot for the SM5814 (thanks for the DS!) its a half-band filter and that's definitely sub-optimal for audio.
http://www.diyaudio.com//www.pinterest.com/pin/create/extension/
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NPC SM5814
I stand corrected on the 12 bit math. The NPC filter may not be a PMD100, however using the same filter as used with the SAA7220 it is far superior. Lower noise maybe why. These days I have moved more toward passive filters as they harm the sound quality less. My ribbon tweeter tells me there is no comparison. The SM5814 beats the SAA7220 every time. Really has to be heard with high hats and flutes. I would be very interested in an emulation project. If you do it I will be watching and waiting to get on board. The TDA1541 really deserves a better filter then the SAA7220. Sadly I don't have the knowledge to design a solution like you suggest. I did look at the PMD100, trouble is they are all used and very expensive. I hope you come up with a better solution. For now I don't miss the SAA7220 at all.I spent some time reverse engineering the SAA7220 - it uses 12bit coefficients, just like the DS says (12*16 multiplier).
Perhaps your reconstruction filter isn't up to snuff? I certainly had that problem (lack of HF clarity) before I built a sharp filter to take out the images - now my HF is as sweet as I need
I'll probably be revisiting my digital filter project sometime later this year, using a new LPC5411x chip from NXP which has the interfaces required along with enough MIPs.... I reckon for digital filters, minimum oversampling is best, 4X seems too high.
<edit> Looking at the FR plot for the SM5814 (thanks for the DS!) its a half-band filter and that's definitely sub-optimal for audio.
I have been through my passive filter stage - now I'm back into active filters once again, this time around though without opamps. Active filters take up much less room - no bulky inductors.
I totally agree that the TDA1541 is crying out for a much better filter - with the latest LPC5411x chip, at last there's a low enough power part with I2S interfaces available to do the job well. I've watched NXP's MCU range for many years now, this new one's exciting...
I totally agree that the TDA1541 is crying out for a much better filter - with the latest LPC5411x chip, at last there's a low enough power part with I2S interfaces available to do the job well. I've watched NXP's MCU range for many years now, this new one's exciting...
I have been through my passive filter stage - now I'm back into active filters once again, this time around though without opamps. Active filters take up much less room - no bulky inductors.
I totally agree that the TDA1541 is crying out for a much better filter - with the latest LPC5411x chip, at last there's a low enough power part with I2S interfaces available to do the job well. I've watched NXP's MCU range for many years now, this new one's exciting...
That makes me "jump for joy", a new filter option for the TDA1541A
I'm going to try Dave's solution in my parallel Red Baron DAC, it's easy enough to build and wire between WM8804/8805 and the TDA1541A.
Thanks Dave, the minnesotan santa was much appreciated
You mean this one: http://www.nxp.com/documents/data_sheet/LPC5411X.pdf ?
Might be interesting if there could be a SAA7220 pin-compatible solution. Plug-in, you know
Yes that's the one - its got two I2S peripherals and plenty of RAM along with very low power consumption (running flat out around 7mA draw for the CPU alone). So it should solve one of the biggest issues with the SAA7220, the fact its so power hungry.
The PMD200 (http://www.hifimaker.com/documents/pmd200.pdf) is just a pre-programmed Motorola 56k DSP so I can't see a reason why an ARM chip optimized for DSP work couldn't fulfill the same function here. All the more fitting that Freescale is now a part of NXP
The PMD200 (http://www.hifimaker.com/documents/pmd200.pdf) is just a pre-programmed Motorola 56k DSP so I can't see a reason why an ARM chip optimized for DSP work couldn't fulfill the same function here. All the more fitting that Freescale is now a part of NXP
Not only power hungry... also an ideal source for digital noise in you powerlines and a real challenge for PSU designers
But looking at the LPC5411x datasheet it's not quite suitable for diy, at least not for me (bad eyes and shaky hands)
The noise and the power hunger are just two sides of the same coin. If the chip didn't need so much current it wouldn't be able to stir up so much noise!
I agree the chip itself isn't suitable for DIYing - I'd not solder it myself either, I'll go looking for a development board on Taobao and if there isn't one I'll just have to create one. The DIY aspect would be in deciding what kind of filter to use, so software DIYing rather than hardware.
I agree the chip itself isn't suitable for DIYing - I'd not solder it myself either, I'll go looking for a development board on Taobao and if there isn't one I'll just have to create one. The DIY aspect would be in deciding what kind of filter to use, so software DIYing rather than hardware.
NPC SM5814
The NPC chip is quite well behaved on power and doesn't tend to pollute the power supplies. Unlike that SAA7220. At this point I can't go back to the SAA7220. I do hope abraxilito takes on the challenge to create a better solution.Not only power hungry... also an ideal source for digital noise in you powerlines and a real challenge for PSU designers
But looking at the LPC5411x datasheet it's not quite suitable for diy, at least not for me (bad eyes and shaky hands)
A friend has designed a board to make it very easy to use. Not sure if he will offer them or not. Wait and see I guess.
Maybe he needs to test them first atleast
Boards...
Absolutely... If he offers them at all.Maybe he needs to test them first atleast
Working on a WM8805 board now.
They are supposedly better than the WM8804?
Atleast they seem more easily available.
I have no skills whatsoever in using the IC in Software mode, so I've designed the board to run in HW mode with PCB switches for setting ouput mode.
Onboard xo with the option to connect an external Clock, cutting connections to the onboard Clock via pcb switches.
I'm using a mix of TH and SMD parts, trying to save space while allowing for TH parts where fancier stuff makes a difference in SQ.
Trying to make this thing as universal as possible so that I can use it with different setups.
They are supposedly better than the WM8804?
Atleast they seem more easily available.
I have no skills whatsoever in using the IC in Software mode, so I've designed the board to run in HW mode with PCB switches for setting ouput mode.
Onboard xo with the option to connect an external Clock, cutting connections to the onboard Clock via pcb switches.
I'm using a mix of TH and SMD parts, trying to save space while allowing for TH parts where fancier stuff makes a difference in SQ.
Trying to make this thing as universal as possible so that I can use it with different setups.
The boards are shipped now
The SM5814 boards that is, I've not sent the WM8805 or the WM8740 boards I've completed(apart from a final inspection or two). Well, not any boards for digital IC's atleast. I did make a 4 rail tracking pre regulator board for my DAC project as I found it frustrating having so many reg boards taking up space.
That board has 2 pos rails and 2 neg rails using 8pcs each of LM317 and LM337.
The dimensions of the board are 95x80mm, that was as small as I could get it and still have adequate(spelling?) heatsinks for each IC.
This board was also made just for personal use, however I MAY have a spare or two as the board houses has minimum order quantities.
I really hope I didn't make any errors given I've ordered two sets of boards now
They did pass software and board house inspection though, so hopefully they're fine.
The SM5814 boards that is, I've not sent the WM8805 or the WM8740 boards I've completed(apart from a final inspection or two). Well, not any boards for digital IC's atleast. I did make a 4 rail tracking pre regulator board for my DAC project as I found it frustrating having so many reg boards taking up space.
That board has 2 pos rails and 2 neg rails using 8pcs each of LM317 and LM337.
The dimensions of the board are 95x80mm, that was as small as I could get it and still have adequate(spelling?) heatsinks for each IC.
This board was also made just for personal use, however I MAY have a spare or two as the board houses has minimum order quantities.
I really hope I didn't make any errors given I've ordered two sets of boards now
They did pass software and board house inspection though, so hopefully they're fine.
I've ordered up some development boards today to kick this filter project back into life. Instead of the LPC5411x chip I've discovered a simpler solution (I hope!) using an STM32F071 or -072. I'll post updates to my blog - that is unless there's a strong demand for a dedicated thread.
http://www.diyaudio.com/forums/blogs/abraxalito/1375-saa7220-filter-replacement-project.html
http://www.diyaudio.com/forums/blogs/abraxalito/1375-saa7220-filter-replacement-project.html