postie1717
Member
I guess Ill be attempting to get someone to fork over the cash to get it professionally looked at, or Ill be bribing people at the theater I sometimes work with to see if they can fix it. Gotta love low budget theaters.
Amplifiers by themselves rarely are a noise problem even when run wide open, the cause of noise and dynamic range problems is usually not with the amplifier itself but rather with the system gain structure prior to the amplifier. So it's not that running the amp wide open is a poor practice or inherently problematic but rather that it is often unnecessary may be indicative of being used to compensate for poor gain structure.It is common and very bad practice to run the amps at full, and the major cause of hum and dynamic range problems, but don't believe me, go to Rane or Yamaha or Mackie or any other source you trust and read how to set your gain structure, this is the best explanation, http://www.live-audio.com/studyhall/gain.pdf others are simpler, but understanding it will transform your sound.
I don't think we really disagree at all and there are indeed many systems run with the amps wide open and resulting poor gain structure. All I'm saying is that the problem is not really that the amps are at "full" but rather the resulting gain structure. An amp being run wide open is not inherently a problem and if approached correctly can be advantageous in some applications, however you are correct that it is probably much more often not approached correctly.In the US it may be common practice to fit pads to adjust the input gain to amps, unfortunately it is not a practice I have ever seen in thousands of installs here in Australia, where it is universal to wind the amps up to "full" and just run the mixer and/or graphics at low level.You are very lucky if that is the situation, I am fighting a losing battle at this end.
You could still have a ground loop created between the devices on a circuit at FOH and devices on a circuit at the amp rack. What often makes more sense than bypassing is breaking the signal paths. Disconnect the output of the console, if the noise goes away then it is probably before that or in the run between the console and the next device. If it is still there then disconnect the other end of that cable, if the noise goes away then it is related to that cable run, if not then it is further downstream in the signal path.Try bypassing the whole rack scene and run a cable from the output of the console to the amp. If it's still there, then the hum isn't coming from anything you bypassed, obviously.
You could still have a ground loop created between the devices on a circuit at FOH and devices on a circuit at the amp rack. What often makes more sense than bypassing is breaking the signal paths. Disconnect the output of the console, if the noise goes away then it is probably before that or in the run between the console and the next device. If it is still there then disconnect the other end of that cable, if the noise goes away then it is related to that cable run, if not then it is further downstream in the signal path.
In this particular case, the swapping of cables at the amps with the result that the problems follows the one speaker and speaker cable seems to indicate that the problem is related to that cable or speaker.
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