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Raspberry Pi with Piano2.1 DAC DSP and Volumio2
Raspberry Pi with Piano2.1 DAC DSP and Volumio2
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Old 26th November 2019, 03:44 PM   #161
Davey is offline Davey  United States
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Quote:
Originally Posted by DonVK View Post
Those curves are for a specific set of drivers and construction. If you swap drivers there is no assurance you'll get the same performance without changing the EQ.
Huh?
I'm well aware of the drivers involved and the specific set of curves required.

The question is whether the designed curves can be exactly replicated with the available processing of the PCM5142. It seems like maybe they can, so that's a good development.

Dave.
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Old 26th November 2019, 04:51 PM   #162
mfeif is offline mfeif
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I certainly don't plan to swap drivers, or even build specs. I'm just hoping to use my Piano 2.1 instead of the MiniDSP.
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Old 26th November 2019, 05:23 PM   #163
mfeif is offline mfeif
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Originally Posted by DonVK View Post
I don't understand. Is this from measuring the response of the DACs? Where is the scaling problem ?
You alluded to it in another reply. It seems that the MiniDSP dev environment one can boost a signal (at least metaphorically in the GUI); in the PurePath environment one can only reduce it.
In SL's curves, there is a dramatic cut of 9.8dB right before output, I bet he's just manually cutting that to keep from clipping. Or maybe the MiniDSP software normalizes too, and that 9.8dB is just to account for the drivers efficiencies. Hard to know.

My concern is that the software is reducing each eq curve by a distinct amount, so all the curves are normalized, but at different rates, which means that they aren't proportional to SL's shapes. For example, he's got one eq boost of 16dB for frequencies below 1000hz, and another about 8db above 8000hz. But PurePath just scales them both; one a lot, one a little, and they both become cuts.


I tried manually scaling them all according to whichever is the greatest factor, then tried and "unscale" them at output, but that looks to be almost 30dB boost, and the blocks won't allow that. So all of these curves add up to a drastic reduction in volume, at least as it *seems*. I haven't been able to measure because I don't have a windows PC with a soundcard (using a Mac laptop with a vm for PurePath and ARTA, and have a linux box with lots of sound i/o)...

I'll have to borrow some equipment so I can measure. Does anyone have a link to a quick tutorial or what-not for measuring the electrical output of a device (not microphone and speakers yet; just hooking the DACs up to a soundcard)?

Don, do you know why in the PurePath environment there are blocks labeled "ROM" and some not? They appear to have the same help files... are the ROM ones perhaps hard-coded and therefore cheaper for the storage/processing?


Thanks for the help wrt negate and so on!
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Old 26th November 2019, 05:26 PM   #164
mfeif is offline mfeif
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Didn't answer one question; sorry. I'm trying to duplicate the digital XO that Linkwitz designed, not the ASP from Mr. Pass.
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Old 26th November 2019, 06:14 PM   #165
PjVervoorn is offline PjVervoorn  Thailand
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Quote:
Originally Posted by DonVK View Post
Right now, based on the files provided, he's at 33% resources on the woofer DAC and 50% resources on the full range DAC.
By using a single dac for left bass and left full range, you average out the resources usage.
Creating the file for the right channel only requires moving one connection between the input and the splitter.


It might even be possible to do a diff between both files, to check if that connection is a single register.
If so, you can generate the -1 file from the -0 file.
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Old 26th November 2019, 08:56 PM   #166
DonVK is offline DonVK  Canada
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Quote:
Originally Posted by mfeif View Post
You alluded to it in another reply. It seems that the MiniDSP dev environment one can boost a signal (at least metaphorically in the GUI); in the PurePath environment one can only reduce it.
In SL's curves, there is a dramatic cut of 9.8dB right before output, I bet he's just manually cutting that to keep from clipping. Or maybe the MiniDSP software normalizes too, and that 9.8dB is just to account for the drivers efficiencies. Hard to know.
That's very likely if the internal number representation is fixed point or integer. I'm not familiar with the internal workings of the MiniDSP.

Quote:
Originally Posted by mfeif View Post
My concern is that the software is reducing each eq curve by a distinct amount, so all the curves are normalized, but at different rates, which means that they aren't proportional to SL's shapes. For example, he's got one eq boost of 16dB for frequencies below 1000hz, and another about 8db above 8000hz. But PurePath just scales them both; one a lot, one a little, and they both become cuts.


I tried manually scaling them all according to whichever is the greatest factor, then tried and "unscale" them at output, but that looks to be almost 30dB boost, and the blocks won't allow that. So all of these curves add up to a drastic reduction in volume, at least as it *seems*. I haven't been able to measure because I don't have a windows PC with a soundcard (using a Mac laptop with a vm for PurePath and ARTA, and have a linux box with lots of sound i/o)...
OK I think I understand. Do not manually use "scaling", just let the software control this. In the PEQ or other EQ biquad blocks you have the "gain" adjustment to boost or cut the signal. I see you already have used it, and in some cases the scaling may change but its not directly related to the gain (ie. 20db gain = 10x, but scaling is not 1/10th). I would consider the scaling an internal issue for the software. I have applied gain to EQ blocks and it works.

Quote:
Originally Posted by mfeif View Post
I'll have to borrow some equipment so I can measure. Does anyone have a link to a quick tutorial or what-not for measuring the electrical output of a device (not microphone and speakers yet; just hooking the DACs up to a soundcard)?
I have loaded REW on the Rpi and used a Umik-1 to measure the acoustic output of a speaker. It is easy to determine if the gains were being applied properly this way. Otherwise you need another soundcard with A/D inputs so REW has control over both I/O on the same platform. It might be possible to "play" a FR sweep file and analyse the output recording but I've never tried it.

Quote:
Originally Posted by mfeif View Post
Don, do you know why in the PurePath environment there are blocks labeled "ROM" and some not? They appear to have the same help files... are the ROM ones perhaps hard-coded and therefore cheaper for the storage/processing?


Thanks for the help wrt negate and so on!
Some program blocks can be held in ROM or RAM and coefficients are always in RAM. When you look at the resources tab you can see how much of a particular resource is being used. It only matters if you're running short of a resource.

Thanks for clearing up 2 issues. You have the same drivers and construction. You want the digital implementation.
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Old 26th November 2019, 08:59 PM   #167
DonVK is offline DonVK  Canada
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Quote:
Originally Posted by PjVervoorn View Post
By using a single dac for left bass and left full range, you average out the resources usage.
Creating the file for the right channel only requires moving one connection between the input and the splitter.


It might even be possible to do a diff between both files, to check if that connection is a single register.
If so, you can generate the -1 file from the -0 file.
That's true, you will get an average, and I've done it both ways. Something to consider when there is a large difference is the channel processing requirements. So far @mfeif is at 33/50% so its close, and you might get a more even 40% by rearranging the DAC assigments.
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