Get one of these. LOL
Posted on 01/14/2014 8:06:39 PM PST by djf
Sound-o-philes!
I have a question.
I have a big mess of wires behind my stereo/tv/vcr/dvd/etc/etc
My main sound setup is a Magnavox dvd/r/rw for vid, I have 2 Behringer a-500 amps (230 WPC each) bi-amped into the original Polk SDA-SRS's (rated at about 3 ohms overall and 1000WPC)
The whole mess is plugged into various power strips and end up going through one of the main circuit breakers in my house (there are 3 or 4 that control various wall outlets).
I have a Kill-A-Watt meter and it easily shows that stereo, at peak volume with a good bass line is drawing up to about 450 watts.
Should I separate out the power plugs to different circuit breakers? I always got the feeling that the amps were trying to draw more power than they could get, even though the breaker never tripped. (But my lights DO dim!!)
Thanks! Just trying to get peak performance!
Get one of these. LOL
But does it go to 11?
I think my neighbors would say “Yup! And then some!”
;-)
Assuming a 15 amp breaker, maximum power is (15amps * 120 volts) 1800 watts. You should be good to go.
450 watts is less than 5 amps (450W/110V). You’re fine with a single circuit.
Yes...that’s exactly what you need to do. I’d put the two Behringer amplifiers on a different breaker. Right now the whole signal chain is sucking power through a straw. When I had my house wired...I had a special 30amp circuit put in to handle the load.
Seriesly, 450W is about 4 amps.
Make sure everything has a good, common ground.
A fast rule of thumb. Separate the amp from the rest of the system power wise.
All should be on good grounding and surge protection. If you have “noisy” power, consider a UPS that has a good source filter for amp. Make sure it is a sine wave UPS. This will help protect the equipment and clean up the sound in a lot of situations.
Thanks! Different opinions, but the type of info I’m trying to get.
The Kill-A-Watt meter can be set to measure the amps being drawn, that will be my next step.
The “sucking through a straw” concept is what I was wondering about. You know, old wiring, you get a little oxidation on the contact points, etc, etc.
I go through a couple cans of contact cleaner a year just working on computers, batteries, whatever...
It’s those transients and peaks, like cymbal crashes or a bass drum thump that require tremendous amounts of power momentarily. If the current isn’t there in reserve for amps...they will hit the upper rails early and flatten out and distort your amplifier’s output. Here’s a good article for you http://www.peavey.com/support/technotes/hartley/Chapter_4.pdf
You can sometimes prevent dimming by changing the placement of breakers, putting the higher draw breakers at the top of the service. You may also need to pull a heavier gauge wire and use a higher amp circuit for your audio system. You don’t say what it is. Just becuse it doesn’t trip, that doesn’t mean you don’t need an upgrade to let you draw more amps safely. Or else split the draw between multiple circuits if that is at all practical. An electrician can give you more specific advice after looking at your service.
Thanks!
Great article and it gives me an idea. The Kill-A-Watt meter can measure voltage. It usually shows 123V on my wall outlets.
I can plug it into a separate outlet still on the same circuit, turn the stereo up, and see if I see a voltage drop.
This is possible if you have wiring done with thin wires (noncompliant with the today's building code.) Then resistance of those wires, under your 4A load, reduces the AC voltage at the input of your equipment. This is easy to test with the same Kill-a-Watt, or with a multimeter (both can be set to measure AC voltage.)
Still, your amplifier should have been designed to tolerate AC voltage in ±10% from the nominal 120V. The 28V, or whatever feeds the final stage, is regulated. Your output power and distortion should not be affected. There is no reason to complicate things unnecessarily. 450W is not a serious load; my electric tea kettle draws 1500W, I think. Dimming of the lights in the house only means that your main connection is not made for what it should have been (100A minimum, and 200A desired.) Or the lights and the amplifiers are on a weak subpanel.
You have gotten some good and not-so-good info.
My opinion is: Don’t worry about it, your setup is OK.
If the lights flicker, and it sounds OK, then you are having fun. Don’t expect better sound fidelity by messing with the power side, unless you are having obvious problems. (Which you are not.)
Let me know if you want a more detailed conversation, tomorrow.
Thanks!
Like I said, I’m just trying to optimize things.
Not an issue of sound quality, the Polks are pretty much flat down to 20HZ or so.
But the amps show clipping at full vol, and are drawing only 450 watts or so, when the total rating should be over 900 watts.
And I’m not sure if the clipping (only at full volume) is because of the speaker draw or they aren’t getting enough from the outlet.
I should probably get two more of the amps so I can mono-block them, run the spkrs at about 900 WPC, and be done with it!
It seems that your speakers are of unusually low impedance. Speaker impedance is not just a parameter. It moves around. You stated that the nominal impedance is three ohms, and also that you bi-amp.
It is safe to assume that the dominant low impedance is attributable to the woofer(s). So your amps may in fact be clipping, or the clipping indication is incorrect, or other conditions.
If it sounds OK, go with it!
Seriously, the first thing you need to do is replace those amps with a pair of Crown Macro Reference units, bridged to mono. That would effectively get you up to 20.
450w is ~1/4th of the safe load on a 20A receptacle circuit. You’re fine.
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