Sunday, March 8, 2015

Balancing Audio ... on the Tip of Yer Nose or Otherwise

Balanced audio is a way to reduce line noise and is typically recognized by three-pin XLR connectors.  The big advantage is that it permits long cable runs without a penalty in noise induced by the length of the run.

Unbalanced audio is typical of guitars, etc which use 1/4" TRS connectors.  Such instruments are also usually high-impedance (i.e. Hi-Z) and this is why their electronic behavior will be different from low-impedance devices such as microphones.  A pre-amp is used to bring a microphone up to line level but plugging a Hi-Z guitar into a pre-amp means you will probably blow it all over the room plus the signal will likely be dirtier because it's an unbalanced input.

This stuff is important but you can't be too much of a purist about it or you will never go on-stage because you won't just use a long cable, you'll use a lot of them.  Staying with ten-foot cables for audio purity is impossible in that environment.  If you have the money for two sets of cables, one for stage and one for recording, good for you but it will put a big hole in your wallet.

This may seem like mindless geekery but it's important to debugging audio problems here in the Rockhouse.  The signal coming into the mixer from the laptop carries the audio for the back tracks.  It is seemingly Hi-Z in that it is very 'hot' and I have to turn the gain on each channel down to zero because there is no Hi-Z switch to tell the mixer to leave it alone.

It seems obvious to solve the problem by attenuating the signal sent from the laptop but that's a Band-Aid as the signal being sent is at the correct level and should not need to be modified.  It's not being handled correctly when the mixer gets it and that's the actual problem to solve.  It has to be solved that way as doing it incorrectly will introduce more noise rather than reduce it.  (The same situation is true regardless of whether I use USB or the cheesy way I'm doing it now in trapping the laptop audio output)

It also seems obvious to replace the cheap-ass mixer with a better one but that doesn't go as the speakers are seriously busted already.  If the question is to replace all of that stuff then that only means I'm officially a non-musico as that would be ridiculous money on top of already ridiculous money for the new used computer.

The reason for the geekage is please do comment if you have anything to add to solving this.


Problem to Solve

The speakers are adequate until they're not.  What I take this to mean is the amps overheat and they shut themselves down.  However, there is no reason for them to overheat as the signal isn't over-driven anywhere.  There are zero indications of clipping on any device in the room.  It's a complex signal path but I check every fookin' bit of it and there are zero red LEDs flashing their anger at me.

So that's the situation for the moment.  This system is running but isn't entirely stable and I'm not sure why it has problems.  It will get stabilized and then I'll schedule a set at the Circus.  It will be bangin' as I'll knock out back tracks one after the other but I have to be sure it will stay stable for an hour before trying that.

Unknown if I mentioned this previously but I counted up about one hundred and sixty knobs on these gadgets and that doesn't count the switches and sliders.  It's not a surprise there are troubles sometimes as the real surprise is the whole thing doesn't explode.

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