Rpi HAT => 8 x differential analog outputs – How interesting? Competition? Difficulties?

[bohrok2610]

What is affected at lower levels is the stereo illusion of sound stage (which is known to be sensitive to phase). A threshold of audibility for average ears for jitter/phase-noise as it affects soundstage is not something I have seen in published research.

Do you know of any studies or similar that can back up your claims?

 

[JMF11]

My STM32F723 based USBI2S bridge has 6 channels with galvanic isolation. Making it 8-channel (or up to 16-channel with TDM) with isolation would be straightforward. But I don't have any use for such device.

Anyhow I don't see the point in all this. Economically this type of endeavour is not very practical as it would be very hard to compete price-wise with e.g. Topping, Behringer or MOTU. Choosing low grade DAC chips to cut costs is just silly.

@bohrok2610 : is your stm32 code shared and open source? Do you shar your 6 channels USBI2S bridge design ?

JMF

 

[Markw4]

Do you know of any studies or similar that can back up your claims?

Don't know of any studies directly looking at a 'threshold of audibility for stereo soundstage perception as affected by clock close-in phase noise using a DSD dac.'

What there is out there that I have found might be regarded as sort of related, but not exactly. One paper with a list of references that might be of possible interest:
https://api-depositonce.tu-berlin.d.../b72a933e-1e9e-4e85-a078-e25ecf80f589/content That said, I have not looked at it in any depth. Don't really see a need to, since some things are quite plainly audible on a good system and this is one of them.

 

[bohrok2610]

The 6 channels on my USBI2S board is configured as 4 out + 2 in. The input I2S source code (and common stuff) can be found here. I presented an earlier version of the board here.

I have a newer untested design for STM32H7 that has 8 channels out but that is waiting for backordered MCU.

 

[bohrok2610]

Don't know of any studies directly looking at a 'threshold of audibility for stereo soundstage perception as affected by clock close-in phase noise using a DSD dac.'

What there is out there that I have found might be regarded as sort of related, but not exactly. One paper with a list of references that might be of possible interest:
https://api-depositonce.tu-berlin.d.../b72a933e-1e9e-4e85-a078-e25ecf80f589/content That said, I have not looked at it in any depth. Don't really see a need to, since some things are quite plainly audible on a good system and this is one of them.

I find it somewhat cheap to counter scientific studies with subjective opinions but I did not expect anything else. As recordings do not specify the width, depth, height or any other parameter of the soundstage all your claims are subjective. And while it may well be audible to you that does not provide any basis for making claims about whether or not the sound reproduction implementation is well made or badly made. Or whether the cause for audible difference is close-in phase noise or something totally different.

 

[Markw4]

We can vary measured close-in phase noise and correlate an audible difference. We find that close-in phase noise affects soundstage in a DSD dac.

Furthermore, it would be hard to believe that reducing phase noise should be expected to make a dac less accurate. On the contrary, I would say reducing close-in phase noise makes for a more well made dac. Others are of course free to disagree.

I will leave off here. You can have the last word.

 

[bohrok2610]

Can you show us a measurement of close-in phase noise of your DSD dac that you base your claim on? And please remember that close-in phase noise of a clock is not the same as close-in phase noise at dac output.