Question for Sylvia: Splitting AV output

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Dear Sylvia,

Let's say I have a video device that has an AV output (3-socket RCA, for video,  
L & R). Can I connect it to the AV inputs of two other video devices (say a TV  
and something else) without loss of quality or blowing anything up? The  
connection would be done by having effectively two AV cables (with 3 plugs each)
 
in parallel connected to said AV output.



Re: Question for Sylvia: Splitting AV output
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Can I chip in here?
Yes it will work, but perhaps not perfectly. It will depend on the
performance of the equipment. The Video portion of the AV signal is
1Vp-p across 75 ohms. Put two devices on that and you will see 0.5Vp-p
across 37 ohms. The weaker signal may cause sync problems (less likely
with modern equipment) and poorer brightness. The audio may similarly
be lower, but you can turn the volume up to compensate. AV switch
boxes are available cheaply, to prevent these signal losses.

Re: Question for Sylvia: Splitting AV output
Brad wrote:
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Certainly.


Thanks. I thought it was probably a bit dodgy. I assume that a switch box (would
 
splitter be a better description?) would require its own power supply, with  
transformer. I was hoping to avoid that.



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A switch box and a splitter are not the same thing. A switch box
selects a different input or output, one at a time. A passive splitter
will reduce the output. An active splitter contains an amplifier, so
full output, but requires a power source.

Re: Question for Sylvia: Splitting AV output
Brad wrote:
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I misunderstood then. I thought you were suggesting a "switch" that would solve  
the signal-loss problem while maintaining the two simultaneous connections. A  
passive switch was my first thought and what I'll probably go with, but parallel
 
connections would be better for my purpose so I thought I'd ask.



Re: Question for Sylvia: Splitting AV output
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As Brad and Sylvia have said, you'll have issues with the video signal - not  
enough to prevent you from seeing it on both outputs, but more than enough  
to drag the video quality into the mud (remember making copies of copies of  
VHS tapes, and how good the resulting recording was?).

If you have $47 to spare, grab this; it'll do the job properly for both  
audio and video, and has four outputs rather than just two;  
http://www.ebay.com.au/itm/121073559070

If you want to save a bit of money and have a 12V power supply of reasonable  
grunt laying around (1A output should suffice), this one does just the video  
for $14; http://www.ebay.com.au/itm/261190349984

Audio isn't a problem unless you're wanting genuinely high fidelity (which I  
suspect you're not); as Sylvia points out, most amplifiers have a  
comparatively high input impedance (generally several tens of kiloohms or  
higher), so there won't be any noticable signal degradation.

--  
Bob Milutinovic
Cognicom


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Very interesting topic. I have done exactly as the original poster has
done and not noticed any loss of quality. But then again, I could
never see what people were going on about HD tv because I could never
really see the difference unless it was on a very large TV set. I
would have thought that high def tv would mean we'd buy smaller TV's
and sit closer to them, not buy bigger sets,  Nobody seems to get
that.

Re: Question for Sylvia: Splitting AV output
On 10/05/2013 8:47 PM, Coach wrote:

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Some equipment has an automatic gain control on the video input, which  
would obviate most of the adverse effects. But it's not part of the  
spec, so trying it in a particular instance is the only way to know  
whether it'll work.

Sylvia.

Re: Question for Sylvia: Splitting AV output
Bob Milutinovic wrote:
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As an audiophile I do want hi-fi sound on one of the inputs (I have the option
of directing its audio to a stereo amplifier and high-quality speakers for
those movies/shows that are worthwhile having hi-fi sound). One of the reasons
for my connection complications is that I prefer the convenience of the plain
TV sound to watch the news or Biggest Loser, but it's not good enough for
Raiders of the Lost Ark. (There are other issues too, such as whether I need a
source to go to recording equpment.)

Thanks for your suggestions. I hoped to avoid another powered device, but I'll
consider it along with a plain switch.




Re: Question for Sylvia: Splitting AV output
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I always suspected you were one. My 6th sense is rarely wrong. Stay
away from primary schools you sicko.


Re: Question for Sylvia: Splitting AV output
On 11-May-2013 9:02 AM, DavidW wrote:
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In that case you will need good quality audio leads. However no 'true'  
audiophile would want anything less than digital audio I would suggest.

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--  
rgds,

Pete
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Re: Question for Sylvia: Splitting AV output
On 13/05/2013 10:29 AM, felix_unger wrote:

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True audiophiles recognise that digital is a quantised approximation to  
the true waveform, and that only analogue media are up to the task of  
faithful reproduction.

Sylvia.

Re: Question for Sylvia: Splitting AV output
On 13-May-2013 10:45 AM, Sylvia Else wrote:

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That's true of course for dedicated audio systems for music  
reproduction. However, when it comes to Audio/Video systems (surround  
sound 5.1, 6.1, 7.1) for watching movies there's no comparison in sound  
quality, if only for the fact that analogue audio is only stereo.

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--  
rgds,

Pete
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Re: Question for Sylvia: Splitting AV output

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Nope, not for any modern digital audio system that isn't broken.


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I'd still prefer two HiFi channels to 7.1 low fi channels. Fortunately both
can easily be HiFi, even if they often aren't.

Trevor.






Re: Question for Sylvia: Splitting AV output
On 13-May-2013 2:16 PM, Trevor wrote:

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So why then do the most fastidious audiophiles prefer valve amplifiers?

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--  
rgds,

Pete
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Re: Question for Sylvia: Splitting AV output

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They're commonly known as audiophools. What people *prefer* does not have to  
bear any relationship to absolute performance, just their personal notion of  
it.
Valve amps are preferred by many electric guitarists for their distortion  
qualities of course, something you may choose to *produce* a certain musical  
"sound", but not a good choice for musical *reproduction* of that sound, and  
certainly not when you don't want that distortion at all.

Trevor.





Re: Question for Sylvia: Splitting AV output
On 13-May-2013 7:07 PM, Trevor wrote:

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So let's see some distortion figures for Hi Fi valve amps vs  
transistor/mosfet amps then

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--  
rgds,

Pete
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Re: Question for Sylvia: Splitting AV output

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amps then

from SC June 2008  Altitude 3500-SS Stereo Valve Amplifier  (RRP $1899)
@32W THD < 0.63% at 1kHz

compare this to two of SCs power amp modules;
from SC January 2004 Studio 350 Audio Amplifier (transistor)
@180W THD < 0.002% at 1kHz

from SC August 2008 Ultra-LD Mk.2 200W Power Amplifier (transistor)
@100W  THD < 0.001% at 1kHz

Also, valve amps have very poor damping factors which means the loudspeaker
cone excursions are not tightly controlled, especially in the 'piston' range
below about 500 Hz. (i.e. muddy bass).











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transistor/mosfet amps then

  Why would we? THD figures are rather meaningless. That they're easy to
measure and quote don't mean they're meaningfull.

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Re: Question for Sylvia: Splitting AV output
On 15/05/2013 12:29 AM, Frank Slootweg wrote:
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**Utterly and completely untrue. THD figures (comprehensives ones, which  
include the spectrum of distortion components) can tell us a great deal  
about an audio product. That said, it is also true that beyond certain  
limits, further reductions in THD may not be useful for humans. Such  
reductions may cause other problems, which can introduce other artefacts  
which humans can respond negatively to.

Make no mistake: An amplifier which exhibits (say) 10% THD _IS_  
introducing it's own signature into a system and is not acceptable for a  
high fidelity reproduction system. An amplifier which exhibits less than  
(say) 0.1% THD is not likely to be so compromised. An amplifier which  
exhibits less than (say) 0.001% THD is unlikely to be differentiated  
from the 0.1% example.



--  
Trevor Wilson www.rageaudio.com.au

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