My church just got new crown amps and I noticed a buzz. They don't have a power conditioner and I think that would clean up the signal. But I'm concerned about something else, they have the amps on stage and the power ran through a light switch in the control booth. Is using a household light switch safe for turning power for amps on and off? I don't seem to think so. The amps that were just replaced really weren't that old and only 1 channel of the 2 ch amps were working on both amps.
Unclean power on amps.
- Thread starterJadams639
- Start date
A power conditioner may or may not help. The first thing you should check for is a ground loop.
Searching on here should provide a plethora of information on how to avoid/remedy it.
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Searching on here should provide a plethora of information on how to avoid/remedy it.
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I believe the OP means that the load of the power amps on the switch may be too much for the switch to handle. A valid concern worth investigating, but if the switch terminates at a receptacle, the switch should be rated for a minimum of 15A.
The hum wouldn't be caused by the switch. The power may be dirty, but the use of the switch would not be the cause of that. I would recommend though that the switch be eliminated from powering the amps if for no other reason than it's very easy for someone to turn off a wall switch in the middle of a show not realizing that the switch is what's powering the audio system.
There are several reasons you could be experiencing a hum in the system. A ground loop is one, a poor gain structure is another. If the gains are cranked on the amps and the signal being input into the amps is too low, the amps will constantly produce unwanted noise. You want to set the console so that it's putting out a strong signal (not so strong that it clips), and then adjust the gain settings on the power amps so that they are a little bit above the "too loud threshold". This gives you some headroom to play with at the mixer the times that you need just a little bit more boost, but any additional gain at the amp is going to introduce unnecessary noise into your gain structure.
Gain structure is only one of several possibilities for a noisy sound sound system though.
The hum wouldn't be caused by the switch. The power may be dirty, but the use of the switch would not be the cause of that. I would recommend though that the switch be eliminated from powering the amps if for no other reason than it's very easy for someone to turn off a wall switch in the middle of a show not realizing that the switch is what's powering the audio system.
There are several reasons you could be experiencing a hum in the system. A ground loop is one, a poor gain structure is another. If the gains are cranked on the amps and the signal being input into the amps is too low, the amps will constantly produce unwanted noise. You want to set the console so that it's putting out a strong signal (not so strong that it clips), and then adjust the gain settings on the power amps so that they are a little bit above the "too loud threshold". This gives you some headroom to play with at the mixer the times that you need just a little bit more boost, but any additional gain at the amp is going to introduce unnecessary noise into your gain structure.
Gain structure is only one of several possibilities for a noisy sound sound system though.
I'd disagree.
Having a switch to turn the amps on and off from the control position can be a helpful thing - but it does need to be labelled...
Mistaking the switch for a light switch is not the problem, all of our techs know this as it has been like that for 20 or more years. The part I'm concerned about it the switching on and off with a switch not designed for this. Could it be damaging the amps?
About the buzz, we are going to be running new speaker wire soon that will be balanced and using xlr to output from the console to the amps, I'm hoping that will clear it up.
About the buzz, we are going to be running new speaker wire soon that will be balanced and using xlr to output from the console to the amps, I'm hoping that will clear it up.
gcpsoundlight
Active Member
That would explain it. Running unbalanced line over large areas is always going to be a problem.
DuckJordan
Touring IATSE Member
How is the switch not designed for this. The switch is designed (very rudimentary) to just make a break in the power line. Its like taking a plug and plugging it in, or unplugging it. A switch is designed to interrupt power, and restore power that is all. Its being used exactly as intended. Whether its a light bulb or an outlet on the other end makes no difference to the switch.
A conditioner wont really help with noise issue. It may extend the life of your amps, and make sure they are recieving 120 volts, and it should help durring a lighting strike instance where it would burn the conditioner instead of the amps. But I don't think investing in a power conditioner to clean up noise is the right thing to do.
Yeah, unbalanced lines can never really make long runs without noise being a major issue. What may have worked before may be acting up now due to a change in the specs/sensitivity of the amps.
Also, until you start spending large sums of money on power conditioners, your not going to hear a difference, much less even measure one. Oftentimes good quality equipment will have more sophisticated line filtering circuitry built in than cheapo power conditioners employ. Really, your low end furman/art/sampson conditioners can be described as little more than powers trips with lights.
Also, until you start spending large sums of money on power conditioners, your not going to hear a difference, much less even measure one. Oftentimes good quality equipment will have more sophisticated line filtering circuitry built in than cheapo power conditioners employ. Really, your low end furman/art/sampson conditioners can be described as little more than powers trips with lights.
We have the amps on a fused power strip, but I don't know if that's as good as a power conditioner
you need to find the source of the buzz.
plug in just the amp + speakers in (disconnect all input sources)
Does it buzz?
if it does try a clean source of power. any change?
does a different amp produce no noise
try the speakers + amp + input cable (no source yet)
nothing is wrong with banana plugs but you do need to make sure that the wiring is consistent.
etc..etc working thrue the signal chain back to the input source.
you should use balanced line or shielded input wire on the Amp input only, not on the amp output to the speakers.
read up on ground loops and re-read MNicolai's post
plug in just the amp + speakers in (disconnect all input sources)
Does it buzz?
if it does try a clean source of power. any change?
does a different amp produce no noise
try the speakers + amp + input cable (no source yet)
nothing is wrong with banana plugs but you do need to make sure that the wiring is consistent.
etc..etc working thrue the signal chain back to the input source.
you should use balanced line or shielded input wire on the Amp input only, not on the amp output to the speakers.
read up on ground loops and re-read MNicolai's post
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JLNorthGA
Active Member
The typical surge protector strips are not as good as a power conditioner - they protect against surges - and that's about it.
Consider getting a UPS (uninterrupted power supply). They will condition your power against surges, spikes, times of lower voltages, etc. They will also provide for a good way to shut the equipment down during power outages. Their cost isn't that different from a power conditioner.
No. Power amps are turned on and off by relays all the time. What turns them off makes no difference. Though I consider the use of a 120v switch undesirable and we wouldn't install a new system based on that method of control, if it works for you then leave it. It's more a matter of a preference and practicality than of anything else. Functionally, it works.
Again -- could be a ground loop issue, could be a gain structure issue. It could also be a lack of balanced lines, but let's clear something up. The only signal that needs to be balanced is the mixer output into the power amplifier. This should be 3-conductor +/-/Gnd. Used to be these were 1/4" or screw terminal terminations, but more and more they're XLR's or XLR and 1/4" combo connectors. Either way, this is the signal that needs to be balanced for best results.
The output of the amplifier should be 2-conductor. If the connectors are banana, 1/4", NL2, NL4, screw-terminal -- it doesn't matter.
Before anything else, I'd look at the gain structure. If you didn't have a problem with hum in the system previously, I'd consider an improper gain structure to be the likely culprit as the gain structure was probably not rebuilt when the new amps were put in. If there's always been a hum, it could be a group loop, but for that matter maybe there never was a tuned gain structure over the last couple decades.
I'd discourage this. Every time you go to kill the amps via the 120v switch, the UPS will go into backup mode and try to keep the system turned on. It'll probably start beeping loudly too to alert you to the fact that there's been an electrical event. Those inconveniences aside, it's unnecessary. Many power amplifiers these days are designed to be operated off of generators or in the middle of a football field. At worse, they'll turn off and go into a self-protect mode. All in all, I wouldn't worry because a church is a fairly controlled environment. If the voltage dips down enough to turn the amps off, you've probably experienced enough of a brown out to also take down your mixer, any computers, and anything else that may be powered in the room.
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If you don't currently have balanced lines run to your amplifier from your mixer, an easy test to do is to temporarily run a couple cables from the mixer into the amps as XLR cables. You can run them straight down an aisle if you'd like. If the balanced lines don't make a difference, another test you can do is to take the mixer and place it on stage. Plug it into the same power source as the amplifiers and see if that resolves the situation or not. If you've ruled out balanced v. unbalanced and a ground loop issue, then the last likely culprit you have control over is gain structure. If not that, then you likely have equipment that's just plain noisy.
I'd recommend you verify that the lines running to your amplifier from your mixer are, in fact, unbalanced. It sounds like you've confused the lines that need to be balanced with the lines that go to your loudspeakers -- the inputs to the amplifier should be 3-conductor, the outputs from the amplifier should be 2-conductor.
You want shielded, twisted pair cable from the mixer to amps and want that to be balanced signals if possible but XLR is simply a connector type that could be used with a variety of signal and cable types whiled speaker wire should not be balanced or even shielded, it should be simple unshielded, unbalanced twisted pair.
As far as the switch, do you know what the switch is actually doing? You noted "amps" as in plural so the switch may not be directly switching a circuit that powers all of the amps but rather switching a control signal that in turn controls multiple power circuits. I would find out more about the power and power switching before looking at that as being relevant.
If you had multiple amps lose one channel than I would be looking at whether those have anything in common and what may be causing that. For example, are all the failed channels associated with one channel out of the mixer or processor or with one speaker? It also sounds as though the only thing that changed when the hum appeared was the amps so have you verified all of the wiring to them was properly terminated?
I take care of a large broadcast facility that includes 14 UPS units ranging in size from 500 VA to 40 kVA. They are a necessary evil for certain things, but powering current hungry things like power amps is not one of them. The beasts are notoriously unreliable and some of the highest maintenance items I deal with. Save the UPS for a digital console with a long boot time, or the computer for video projection.
I have yet to ever find an audio noise problem that was caused by anything happening on the line cord. I view so called power conditioners as nothing more than snake oil, too. The rare exception to power conditioning is a ferroresonant regulation transformer, such as a Sola Constavolt. They are big, heavy, and noisy and expensive. The only place I would use one is where power quality has observable problems. Fix the audio noises through proper audio wiring methods.
If surges and lightning are a concern, a plug strip won't do it. A power conditioner won't either. The best way to deal with this is a properly sized surge arrestor at the building entrance panel, and another at any subpanels that serve technical systems. In Florida, it would certainly make sense to spend some money with a qualified electrical contractor to install surge suppression.
I agree with this, but with an addition. Even with balanced lines, it is common practice to have to drop the shield connction at one end of the line, when the interconnected equipment is fed from different power sources, or is physically separated by long distances. It seems counter intuitive to break the pin 1 connection to the cable shield at one end of the cable, but it works, and for good reason.
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