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Merging digital signals
Old 24th July 2005
  #1
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Keyplayer's Avatar
 

Merging digital signals

I already know that you can't merge digital signals (there's no such thing as a lightpipe "Y" jack). I've just never understood why. What is it about digital that's so different from analog in this regard?

You can run 24 channels of adats or DA-88/78's through a digital mixer and print it to a DA-30 or Masterlink. So, to me that's merging (some might argue that it's really streaming). But you couldn't take 2 digital mixers outputs into one DA-30 or Masterlink. Pointing out the obvious only one input on these devices is NOT the point. If it were analog, I could simply get a "Y" jack to accomplish this task. But the option doesn't exist in digital and THAT'S the core of my quesion. Why can't you merge digital signals?
Old 24th July 2005
  #2
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gyraf's Avatar
 

because digital signals are not signals in the classic sense, they're simply a serial stream of binary numbers that need conversion and processing to make any sense at all.

If you simply merged two digi signals, you'd screw up the timing information in both and destroy all information in there.

To do digi mix, you need to dechipher the serial digi streams into a stream of parallel "real" x-bit numbers/values, then multiply these with a constant (mix level), then add the two (making sure that you don't exceed the number of bits wanted), and reduce result to be within your wanted bitdepth.

A simple addition of "real" x-bit values wouldn't do either, as two 16-bit figures would on average add up to a 17-bit number - so some data reduction is necessary, e.g. removal of lsb.

It's fair to say that digi mixing is far, far more complicated than it's nalog counterpart. Which is also the reason for the huge difference between analouge and digital mix quality.

Jakob E.
Old 24th July 2005
  #3
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max cooper's Avatar
 

You can't properly merge audio with a 'Y' cable either. You CAN use a 'Y' cable to send one source to two places.

The reason you can't merge two digital signals with a 'Y' cable is that the result would be some kind of goobledygook that wouldn't make any sense.

Was that technical enough?
Old 24th July 2005
  #4
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Quote:
Originally Posted by max cooper
The reason you can't merge two digital signals with a 'Y' cable is that the result would be some kind of goobledygook that wouldn't make any sense.

Was that technical enough?
Keyplayer: Yep, that was just fine!
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