Battling the overly hot output of cdj2000's

[byacey]

I'm well up on my theory; I'm an accredited CET.

The filter caps will not sustain much power for any period of time; perhaps a second or so in a typical amp. However, the filter caps are not some magical reservoir that provides momentary peak voltages that far exceed the maximum RMS power output. To be exact, under ideal conditions, you will get audio peaks that are 1.414 times the maximum RMS voltage out. The real job of the filter caps is to provide a stable DC power supply rail voltage with minimum 120 Hz ripple in a conventional transformer derived power supply. In a switching supply, the purpose is the same, but the filter caps are much smaller due to the ultrasonic switching frequencies. The power supply rail voltage of the power amp defines what the possible peak output voltage is.

The highest peak output is determined by the DC value of the power supply rails; in a good amp, the maximum peak audio output will be slightly less than the rail voltage, by a volt or 2, due to losses across the output transistors and emitter resistors. This peak voltage is simply 1.414 times the RMS voltage out.

Most respected manufacturers specs are based upon this voltage, and load testing with a sine wave signal generally measures pretty close to the RMS specified power. As an example, if you have an amp rated 625 WRMS across an 8 Ohm load full bore, both channels driven, you're just not going to realize any more power than this, unless the power supply is some sort of perpetual motion device.

Back to the original posters question - If you are using your power amps anywhere near full power capacity, ensure you have a 15A circuit per every 1500W RMS of amplifier power. Anything less, and you will run into line voltage sag, and potentially tripping circuit breakers during the performance. If you're just playing loud music in the backyard or some other non demanding situation, yes- you can likely get away with a single 15A circuit provided nothing else is on the same circuit as that particular wall receptacle you chose, but it's not a good or reliable practice.

In the pro industry, a 50A 240V, 100A 240V or three phase circuit is dedicated for audio in larger venues. This would go to a large stage side distro that has it's own breaker panel splitting out into a number of lower current branch circuits, and typically 20A for every power amp. Each amp rack would be fed with a high current 240V split circuit, and then have it's own separate small distro that houses the 20A breakers and receptacles for each amp. The other advantage to this is if a catastrophic failure befalls one of your power amps, the dedicated breaker will flip, but the other amps will continue working normally instead of the complete dead silence that would occur if you were running everything off one circuit.
Here's some examples of what I mentioned: http://www.unionconnector.com/portable- ... nt-distros

[byacey]

If you're playing a straight 60hz sine wave, or lighting a light bulb yes, you're correct. However, music program ebbs and flows, and capacitors in amps can buffer the unused current to produce higher peaks powered by the excess current from lower valleys.

The is no such thing as unused current. It either flows or it doesn't. In a power amps DC power supply, the caps charge up to their maximum voltage at idle. Under full power conditions, this voltage will drop minimally unless it's a really crap, flimsy, poorly designed power supply, or the filter caps are dried out with age and heat. As I mentioned in my previous long winded post, that DC voltage sitting on the caps dictates the potential peak audio voltage possible and by extension, the maximum RMS voltage available. Nothing more.

Here's some further reading for those inclined:
http://www.rocketroberts.com/techart/powerart_a.htm
http://www.rocketroberts.com/techart/amp.htm
http://www.rocketroberts.com/audio.htm

[5meohd]

Thanks. I'm a little concerned with the cost of doing this properly (as the site you recommended does not have prices listed). Also the fact that most venues I've been to don't have the 3 phase option. Luckily the venue this Saturday DOES have 4 separate 20A sockets and I'm only running 3 amplifiers. Is this an example of where I may run into ground looping?

thanks for all the info guys.. I'm all ears!

[Grant Bunter]

Luckily the venue this Saturday DOES have 4 separate 20A sockets and I'm only running 3 amplifiers. Is this an example of where I may run into ground looping?

Ground looping shouldn't be a problem if all the sockets have a common earth.
Try to run your other gear on of the same circuits as the amps.

[5meohd]

btw this is the conditioner http://www.furmansound.com/product.php? ... id=PL-PROC


I guess this was massive waste of money!!

[5meohd]

also

http://www.pioneer-latin.com/downloads/ ... ar_low.jpg

where is the pad switch?

[racertomtom]

[88h88]

also

http://www.pioneer-latin.com/downloads/ ... ar_low.jpg

where is the pad switch?

Pad switches are on the mixer, certain models of Pioneer anyway, the ones usually used 'professionally' like the;

DJM800 (to the right of the master outs)
http://www.djworx.com/skratchworx/image ... 0_back.jpg

DJM700 (again to the right of the outs)
http://www.djresource.eu/images/topics/ ... 0_rear.jpg

DJM2000 (same place as before)
http://djservice.se/db/bilder/produktbi ... 9472_3.jpg

The annoying thing about Pioneer is there's no real 'standard' they build things to... ALL models should have that switch really.

[5meohd]

maybe the nexus has it in the software?? I tried skimming the manual and found nothing. shit.

[sine143]

why do you keep posting pics of cdjs? and not the MIXER? cdjs go into the mixer, then sound comes to you (or thats how it suppossed to work. Pioneers line of mixer is the DJM. YOu can find the pad on the 700, 800, 900 and 2000.

[5meohd]

merp.. that makes sense. I'm an idiot. Thanks.

[sine143]

haha, no worries mate! just trying to point you in the right direction. what is your dj using for a mixer?

[5meohd]

well we use the allen & heath xone 92... never have any issues.. but most guys request the djm900.

[sine143]

you can pad the 900 but its a little trickier.... RTM