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48 kHz outboard on 96kHz backbone? Multi-Effects Processors (HW)
Old 26th January 2019
  #1
Gear Head
48 kHz outboard on 96kHz backbone?

Running a Dante backbone at 96kHz, I wonder what the best option is to add a tc electronics fireworx to the setup:

1. Digital Connection, SRC. Fireworx runs at 48kHz, but offer AES/EBU I/O. So SRC comes to mind, available in "single" units such as Audinate AVIO AES3 (170 new) or in "pairs of 4" such as focusrite d16aes (1500 new) or SSL X-Logic Alpha Link MADI SX (1000 used). What would be the things to look out for, as 48/96 seems to be "just" conversion at factor 2. But I wouldn´t be surprised if SRC is not as easy as it looks, even if we just look at half/double sample rates. The fireworx would be syncing to the AES/EBU WC coming from the backbone.

2. Forget about this, just go analog and use existing ADC/DAC.

3. The fireworx may be used as an insert FX or on an aux bus, that varies.
Old 26th January 2019
  #2
Lives for gear
You turn it on or you turn it off. That’s all there is to it. There is nothing not easy about SRC; you won’t need a Ph.D in electronics.

Or do analog. Or run all 48k.
Old 26th January 2019
  #3
Gear Head
Hm, I would have expected a bit more wizardry behind SRC, like:


Downsampling (96to48) seems easy, kind of a lossy compression , just take every second sample value from the 96kHz and put it in the 48kHz stream.

Upsampling (48to96) however is adding sample values and could be done in a variety of ways: let´s say (referencing the 96 stream) the odd sample values (1,3,5,7...) are the 48kHz signal. Then there are a few options to calculate the even sample values (2,4,6,8...)

a) Keep the last odd value (kind of sample/hold), so if the 48kHz samples have values of 100,150,200, the 96kHz samples would be 100,100,150,150,200,200.

b) Or you may interpolate just between two samples, so it would be 100,125,150,175,200

c) Or you may add some sort of weighting, prediction etc based on the past samples, but I don´t know much about those algorithms.

So at least between option a) and b) there is a difference: Question is: do different vendors implement SRC in different ways? And of course: Is that difference directly audible (golden ears) or is it possibly leading to audible differences/artefacts when doing heavy processing. This at least seems to be one point why people choose 96 over 48.


But you´re right, with 48 not being an option, I should just try SRC vs analog and see if it makes a difference. However, now I´m curious
Old 26th January 2019
  #4
Lives for gear
 

That is not how downsampling or upsampling work. Understandably, a lot of "users" do think simple approaches are used (every other sample and doubling) which leads to people also being confused about the quality of these processes (like thinking that doubling or halving sample rates is cleaner/more accurate than going from non-even conversions)

And yes, vendors use different methods (algorithms to sample rate convert and filters applied.) A lot of research has been put into many methods to do both downsampling and upsampling and every vendor implements what they choose (or license it from some other company)

Last edited by pentagon; 27th January 2019 at 01:27 AM.. Reason: typo: that -> than
Old 26th January 2019
  #5
Gear Head
Thanks for confirming my suspicion I picked the simplest options (as wrong as they may be) to show that there are a few options how things could be done.

So now I need to do two things:
- Get myself educated how up/downsampling can be done, at least the basic principles
- Compare the devices I mentioned above, if the vendors are willing to disclose. Probably not, so I´ll a/b them and see/hear if the different methods give different results and if my ears care.

Do you have any good resources on how SRC works?
And what is a valid test setup: 96-48-96 conversion and then see if the inverted result nulls the original?
Old 26th January 2019
  #6
Gear Addict
 

Dante AVIO’s don’t SRC. Just get a rednet
Old 26th January 2019
  #7
Gear Head
Quote:
Originally Posted by Perelandra05 View Post
Dante AVIO’s don’t SRC. Just get a rednet
Are you sure? According to their datasheet, they do "Asynchronous Sample Rate Conversion" (Dante AVIO Audio Network Adapters | Audinate), scroll down to the table at the end of the page.

Or is "asynchronous" SRC some special marketing term to make you imagine it´s doing something, which is actually not? Does it maybe mean: We just resample, but don´t sync the stream and transcode?
Old 27th January 2019
  #8
Gear Addict
 

Quote:
Originally Posted by c00kie View Post
Are you sure? According to their datasheet, they do "Asynchronous Sample Rate Conversion" (Dante AVIO Audio Network Adapters | Audinate), scroll down to the table at the end of the page.

Or is "asynchronous" SRC some special marketing term to make you imagine it´s doing something, which is actually not? Does it maybe mean: We just resample, but don´t sync the stream and transcode?
100%. I have a few dozen of them.
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