freeDSP-aurora - DSP with 8 I/Os, USB Audio, S/P-DIF, ADAT, Bluetooth and Wifi contro

HumbleDeer

Member
2016-10-05 2:50 pm
Yes, agreed. I was just thinking about the various failure modes but I am overthinking it.

What happens if the shield is connected at both ends? Wouldn't the shield be more effective at rejecting interference?
Yes. It would. But it would also cause a literal loop. A loop where one potential is greater than the other because one is closer to noise AND has more surface area. That negates the the benefit
 
Could someone help me troubleshoot the S/P-DIF input please?
I have AddOn B connected to my Aurora. I verified that all the ribbon connectors between the AddOn and Aurora are properly installed.
The S/P-DIF from my PC's motherboard is connected to the first S/P-DIF input of the AddOn.
From the web interface I have configured the audio to be routed to Output1 and Output2 but I get no sound at all.
I tried all 4 inputs with the same result. USB audio works fine.

1645267152837.png


Plugin version: 2.2.1
FW version: 2.2.1
I also have a volume Potentiometer connected.

Any help is appreciated, thank you!
 
now, I dont have this board, nor am I familiar with it, but just looking at your matrix mixer there (to use an RME term), although you appear to have spdif selected as an input and output on the left tab (outside the mixer on the left), your spdif output listed underneath as output 1 and 2, is referring to outputting spdif channel 1 and 2 to the spdif digital output on the add on.

As far as your audio output, you havent got spdif selected as an input for any of the 8 channels, you have USB 1-2 from input channel 1-4 mapped to OUT 1-4, then 4 analog inputs (analogue 5-8) mapped to OUT 5-8. Nowhere is spdif shown as a selected input to the mixer. Again, it seems like you are mistaking your S/P-DIF-Output Left Channel = output 1 Right Channel = Output 2, as meaning you get spdif at the output? I may have misunderstood.

If I understand the mixer correctly, you should try selecting spdif input channel 1 and 2 as the inputs for all 8 channels, or however many output channels you want to use. if you are using outputs 1-2 (ie, if thats where you are connecting your cables), you should select where it says USB 1 and USB 2 to being spdif input 1 and 2. Then it will be selected for that preset and you can go about making your changes to the filter.
 
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Yes, I would expect your last setting to work and give you output on channel 1-2, provided everything is working and you have tested the computer as a source using optical with something else. Someone familiar with the board will be better from here i'm afraid.
Yes, someone who has used the specific board and configuration might know what's wrong. In any case, I appreciate you trying to help me out with this!
 

tomik

Member
2019-04-04 5:56 pm
Yeah, I've tried many combinations of inputs and outputs but none works. I tired this one following your suggestion which doesn't work either:
View attachment 1026909
You should get audio from optical1 to OUT1/2 in the example you have given. I have noticed you sometimes need to toggle the S/P-DIF setting on the left to get it working (so select for example Optical 2 and the Optical 1 again).
 
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tomik

Member
2019-04-04 5:56 pm
I'm planning to do some modifications to the main PCB design. Namely change the DAC output stages (opamps) for +/-12V supply and some changes to the VREF/AVDD bypass (got some ideas from AK4468 ds and evm user guide). When I open the Kikad project it is missing some component library files (rk.lib and rkdev.lib). Would it be possible to get those uploaded to github?

I'm seeing some second harmonic increase at higher output levels which I assume comes from the fact that the opamps are working very close to the clipping limit (common mode voltage range). So I'm trying if I can improve this with dual supply for the opamps. And I could get rid of the output caps on the signal path at the same time. Also I think the overall noise floor could be further improved.


On the noise floor topic second question. When I use the aurora dsp digital volume control I can see the noise floor change. With close to 0dBFS noise is highest and with lower amplitude the noise also reduces. But if I change the signal amplitude upstream (digital in to the aurora dsp) the noise floor is constant regardless of the signal amplitude. I cannot really understand what is the difference here? Is it somehow related to some quantization noise in ADAU? I'm not an expert on digital signal processing, but like to learn :)


Oh, one more thing why this full scale THD/noise floor matters to me is that I'm planning to do analog volume control. So basically the DSP would be at full volume all the time and I would reduce the amplitude in analog domain.
 

hunterst

Member
2014-06-29 8:30 pm
You should get audio from optical1 to OUT1/2 in the example you have given. I have noticed you sometimes need to toggle the S/P-DIF setting on the left to get it working (so select for example Optical 2 and the Optical 1 again).
Thanks for the suggestion @tomik but unfortunately that didn't work either. I tried all S/P-DIF inputs but no sound.

Another strange thing I noticed is if I set SPDIF L and SPDIF R as inputs for Channel1 and Channel2 respectively, there is DC current going to the speakers (cones get pulled in). Could that be a sign that something is broken?

Thanks!
 

tomik

Member
2019-04-04 5:56 pm
Thanks for the suggestion @tomik but unfortunately that didn't work either. I tried all S/P-DIF inputs but no sound.

Another strange thing I noticed is if I set SPDIF L and SPDIF R as inputs for Channel1 and Channel2 respectively, there is DC current going to the speakers (cones get pulled in). Could that be a sign that something is broken?

Thanks!
Yes that definitely does not sound good.. Is it the same with any optical input? Have you tried with coaxial?
 

tomik

Member
2019-04-04 5:56 pm
Finally got the redesign of the aurora board assembled and first tests done. So basically I have redesigned the analog buffer part of the board with fully differential opamps, updated the power tree and then used 4-layer board instead of 2-layer. THD+N with the original aurora board was -100…-105dB depending on output, THD -100…-110dB. Now with new board THD+N -108…-109dB, THD -112…-115dB. Noise levels are lower and supply spurs are gone.

Happy to see even better THD+N results than on AK4458 EVM 😊. I still need to check what is causing increase on jitter, that is next on my list. I’ll post some pictures and test results once done.

Btw I’m using E1DA ADC (with REW) for testing, excellent device with low price!
 
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