Battling the overly hot output of cdj2000's

[5meohd]

We had the first gig using four tuba 60's and we had the standard issue. Djs using cdj2000 or serato giving us a terribly hot signal. Even at time when the pioneer mixer wasn't red lining the qsc plx2 and mackie thumps were. This is very strange. Our fix was to just turn the amps down and let the headliner red line. Sounded a little crushed but it did seem louder and the amps never red lined again. Keep in mind this was with the bss 31 band eq gains turned to -9 the whole night.

I think using something like the radial step down boxes between the cdjs and mixer input would work? The are made to take consumer +4 devices to -10.

We also had our furman power conditioner trip when the headliner started. Unfortunately I don't have the manual in front of me but I think the led meter on the front shows the voltage we were pulling? Makes since because it would go up every time the amps or thumps red lined.

[sine143]

what mixer do you use? pioneer 800 and 2000 have neg 12 pads on the back

doesnt matter how hot a cdj is if it goes through a dj mixer first. either scream at your djs till they get the picture (good luck), or use the above mentioned solution.

[Bill Fitzmaurice]

We also had our furman power conditioner trip when the headliner started.

I hope not connected with the power amps. Power amps should not go through anything but a power cord.

[Bas Gooiker]

Get a FOH mixer so you can turn them down if they keep on trying to fry your gear.

Or a baseball bat usually works wonders as well...

[5meohd]

what do you mean about the power amps not going through a conditioner?

[Bruce Weldy]

what do you mean about the power amps not going through a conditioner?

He's saying to not plug you amps into the power conditioner. I run mine all through a power conditioner in my rack, but I'm using all new, light, low-power consumption amps and have never had a problem - but I've had 'em trip with bigger amps.

[Bill Fitzmaurice]

what do you mean about the power amps not going through a conditioner?

Because power conditioners can choke off current delivery. BTW, 99.9% of whatever 'power conditioning' gear requires is done by the gear. Not one amp manufacturer recommends their usage, while many recommend against it. OTOH most so-called power conditioners are actually just surge protected power strips anyway. Oddly enough the more expensive it is the less likely you really need what it does.

[5meohd]

so what is the right tool for combining the plugs. I doubt that I will have the option to plug all 5 amps in at some of the smaller venues..

[Bruce Weldy]

so what is the right tool for combining the plugs. I doubt that I will have the option to plug all 5 amps in at some of the smaller venues..

Use a standard power strip or build a break-out box from the electrical aisle at Home Depot. $10 should do it.

[byacey]

Plugging more than one 1500W amp into a 15A circuit is asking for trouble if you're working them at all. The proper way to do it is with a real AC power distribution panel. I don't know what power amps you have, but you should have an individual 15A circuit for every 1500W of audio power.

If you're running low power demands, you may get away with a single 15A circuit.

[BrentEvans]

Plugging more than one 1500W amp into a 15A circuit is asking for trouble if you're working them at all. The proper way to do it is with a real AC power distribution panel. I don't know what power amps you have, but you should have an individual 15A circuit for every 1500W of audio power.

Not necessarily. My whole system runs easily off of two 15A circuits, and I have a total of 19000W (rated) of amp power. Of that rated capacity, about half of the current is available for use (about 9000W) based on speaker impedance. Even so, two 15A circuits do quite nicely, as program content simply doesn't sustain max levels. I can push the whole rig into clip without tripping a breaker.

Ohm's law is a bit deceptive as it comes to power amps. Audio isn't sine waves, and finding program power isn't as simple as calculating watts from volts and ohms, as the voltages are different across the bandpass. What matters is RMS power, which is the area under the curve of the audio waveform, where the waveform represents the motion of the speaker. Note that this is also separate from the concept of voltage limiting, which we do to control excursion on horns which don't complain audibly.

[byacey]

As I mentioned, if you're not working the power amps, you can get away with it, depending how loud you're running. If you have four 8 ohm subs pounding near the -3db point, it definitely becomes a concern. I don't know what gear you're running, but I've seen FOH processing racks and the mixer power supply draw 5 or 6 amps alone, before even considering power amps and stage backline power.

Music or program power doesn't mean anything to me; there are various methods of arriving (read "fudging") that rating. Watts RMS is the only concrete and meaningful measurement that I know of in assessing a power amp. We measure voltage and current from the wall socket in terms of RMS values. For those that would rather think in terms of RMS volts across a specific load impedance, it's just as ludicrous to try and rate an amp output in terms of "Music Volts".

I've been lead tech on enough shows to know that you don't want to be loading up a single 15A circuit with five 1500W amplifiers, especially for high profile and televised events. Can you imagine telling the producer on a live, nationally televised event to just hold on while I go find the breaker panel to reset the breaker for the subs? Only to find some guy backstage trying to run a coffee maker on the same circuit?

Here's a little chart I just found on QSC's website. Their amps are of average efficiency, so it can be used as a general guide.
http://qsc.com/files/3513/6494/5342/QSC ... N_RevA.pdf

[byacey]

Not necessarily. My whole system runs easily off of two 15A circuits, and I have a total of 19000W (rated) of amp power. Of that rated capacity, about half of the current is available for use (about 9000W) based on speaker impedance. Even so, two 15A circuits do quite nicely, as program content simply doesn't sustain max levels. I can push the whole rig into clip without tripping a breaker.

All you're going to get from two 15A circuits @120V is 3600W RMS. Figure on about 10 to 15% losses in the power amps, subtract whatever current your processing uses, and you'll be close to a real world power output RMS.

[5meohd]

well the conditioner was a 20 amp model and on a proper extension cable into an outlet that had the proper socket. however, I am positive I don't know enough about this and I NEED to find out more.

[BrentEvans]

All you're going to get from two 15A circuits @120V is 3600W RMS. Figure on about 10 to 15% losses in the power amps, subtract whatever current your processing uses, and you'll be close to a real world power output RMS.

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 "watts" value your amp is rated for is a calculated product of the voltage that amp can deliver into a given impedance over a given time interval, governed by the capacity of the capacitors in the amp.

It is not only the amplitude (height, voltage) of the wave, but the shape of the wave that determines current (watts, area under the curve of the wave). To illustrate, notice the square and sine waves in the diagram of the same voltage... but the square wave has far more RMS current.



The same is true of music program versus straight sine waves. Thusly, amps can push out brief periods of power from their capacitors above the "limit" of 1800w or 2400w.. but.....

Even those figures are time limited figures. Check out the spec sheet for the Peavey IPR series (my amps). It specifically states that max output is limited by the circuit breaker. In the same manner, the 15A or 20A circuit breakers will actually exceed that rating for a brief period of time before tripping. This is why your lights can dim when you turn on a big motor... you're actually drawing way more inrush current than the breaker is rated for.. but only for a moment. Amps work the same way.

Lights... totally different story. Why? They're using straight 60hz AC sine wave (or what passes for that on the electrical grid). Thus, all conventional wisdom applies.