[mythtv-users] New system spec -- seeking comments.

Robin Hill myth at robinhill.me.uk
Tue Jun 10 15:24:49 UTC 2008

On Tue Jun 10, 2008 at 08:10:12AM -0700, Allen Edwards wrote:

> > If you have the option for optical into your pre-processor, take it.
> > It will eliminate any possible interferrence (hum, hiss, whatever)
> > that may occur in the connection.
> >
> > Kevin
> > _______________________________________________
> Interesting input. I have used Coax S\PDIF inputs for years and never
> had a problem.  I don't really understand the benefit of optical and
> am not sure why people use it, to be honest.  You just need to be
> careful of your grounds, make sure they are all the same reference.
> You need to do this anyway as you are going to have video connections
> that are not optical.
Optical just eliminates any issues with interference over the
connection.  However, most systems use very cheap optical parts, so you
end up with added interference/errors in the electrical/optical conversion
process instead.  Overall I doubt there's much in it, unless you're
running the connection through a particularly noisy area.

> Of course, my system is very complex and I go to great lengths to
> insure no ground loop problems.  For example, I run a dedicated power
> line in the ceiling and wall from my projector to my amplifier so they
> are fed off the same circuit.  I also have ground breaking
> transformers on the antenna lines that go to other rooms in the house
> so that I don't get hum that way.  But S/PDIF itself is digital and
> not subject to interference.
Digital is still subject to interference - it just manifests itself
differently from analogue interference.  Minor interference will be
ignored whereas more significant levels will cause data errors and very
noticeable changes in the audio output (pops, silences, etc).

> The bottom line is my pre-processor has a limited number of optical
> inputs.  I use them for the equipment with no coax and use coax for
> the rest.  Myth will be on Coax for that reason.
Yeah, that's as much a deciding factor as any (probably unmeasurable)
difference in quality.

    ( ' }     |       Robin Hill        <myth at robinhill.me.uk>  |
   / / )      | Little Jim says ....                            |
  // !!       |      "He fallen in de water !!"                 |
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