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Author Topic: 6dB drop in balanced audio channel  (Read 4605 times)

absolutkj

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6dB drop in balanced audio channel
« on: November 07, 2005, 12:03:43 PM »

I'm new at this, but I know this is a simple question.  What is the most likely cause of a 6dB drop in a balanced audio channel compared to its equivalent channels?  Does this have something to do with shorting of wires?
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Tidewater

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Re: 6dB drop in balanced audio channel
« Reply #1 on: November 07, 2005, 12:07:26 PM »

In what type of machine? Has trs 1/4" too? Tried all ins?

Just use that channel for banjo.


M
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BoMoFo

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Re: 6dB drop in balanced audio channel
« Reply #2 on: November 07, 2005, 12:51:55 PM »

Simplest explaination would be that you are missing a hot or cold leg somewhere.  Whenever this happens the resultant is normally a "-6 dB" situation.  Inspect the connectors through the path on that channel.  and if you can check for continuity throughout the path.  it could be as simple as something in the wrong with an xlr jack or plug.

B!
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drknob

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Re: 6dB drop in balanced audio channel
« Reply #3 on: November 09, 2005, 11:51:23 PM »

I shall try to restrain myself, because this is a symptom (probably) of 'kinda' balanced lines. Given a true balanced line (the signal is defined as the difference between the two legs), if one side is open (unterminated) the signal is undefined. Without getting into it too far, it will sound like crap. A 'kinda' balanced line (differential output) may sound alright, but will lose 6dB under two conditions. First, if you feed an unbalanced input, half the signal will short to ground. Hence -6dB. You will also observe the same effect if one leg is simply disconnected. A true balanced line (requiring a transformer or some clever electronic bits) does not behave thusly. Here's the real news: Digidesign and most current manufacturers do not use real balanced outputs. (They're more expensive to manufacture.) This means it's impossible to mix balanced and unbalanced gear in a patch bay without associated 6dB losses. Bit of a mess, wot?
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Harold Kilianski
CIRMMT, McGill University

Brian Roth

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Re: 6dB drop in balanced audio channel
« Reply #4 on: November 10, 2005, 03:56:19 AM »

Siiigh..the bane of our existence is the mixture of bal/unbal, particularly within a patchbay.

It began "innocently enough" as some manufacturers began doing stuff like "insert outs" on a desk being unbalanced.  But, when they cheaped-out with "unbalanced insert returns" all hell began to break out.

Bri

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dcollins

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Re: 6dB drop in balanced audio channel
« Reply #5 on: November 11, 2005, 02:13:29 AM »

Brian Roth wrote on Thu, 10 November 2005 00:56


It began "innocently enough" as some manufacturers began doing stuff like "insert outs" on a desk being unbalanced.  But, when they cheaped-out with "unbalanced insert returns" all hell began to break out.



And so became 6dB a Magic Number in The Interfaces.

DC

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Re: 6dB drop in balanced audio channel
« Reply #6 on: November 11, 2005, 06:28:25 PM »

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Brian Roth

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Re: 6dB drop in balanced audio channel
« Reply #7 on: November 12, 2005, 03:34:53 AM »

LOL!, Bill!

Bri

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Brian Roth Technical Services
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Re: 6dB drop in balanced audio channel
« Reply #8 on: November 15, 2005, 01:35:03 PM »

 Very Happy
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Larrchild

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Re: 6dB drop in balanced audio channel
« Reply #9 on: November 29, 2005, 04:11:02 PM »

I see the analogy here. Much like your missing + or - on that xlr, these foil hat guys are exactly 6db shy of a full deck. Nice analyzer, though.
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Larry Janus
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