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XLS402 distorting


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#1 RPMazzi

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Posted 03 October 2006 - 04:12 PM

I bought an older one speakon XLS402 and am using it for my bass rig with an Ampeg SVP-CL to power two 8 Ohm avatar cabs. I am bridging the amp with a banana cable and am using a xlr 'Y' for the input. The cabs should be able to hold the power, but they are distorting even at moderate volumes. To boot, the whole unit is much reduced in volume than my previous bass amp which was only 400 watts. If you simply looked at the speakers you would think it was knocking people off their feet with the cone travel, still no volume. Its loud, but the 1100 watts sound more like 200.

#2 MChapman

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Posted 04 October 2006 - 12:36 PM

QUOTE(RPMazzi @ Oct 3 2006, 04:12 PM)
I am bridging the amp with a banana cable and am using a xlr 'Y' for the input. The cabs should be able to hold the power, but they are distorting even at moderate volumes. To boot, the whole unit is much reduced in volume than my previous bass amp which was only 400 watts.
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You state that you are using the XLS-402A in the bridge mono mode. Did you modify the wiring on the channel 2 side of the "Y" cable per the instructions in the owners manual? If not, that would explain everything you are seeing. Because the amp does not have the bridge-mono switch on the back of the unit, you must use the "Y" cable to input the signal on both sides, and invert the polarity of the signal on ch 2. This is done by simply swapping the wires that are on pins 2 & 3 of the ch 2 XLR cable. You must also use both pots and set them at the same level. I would suggest labeling the XLR's as ch 1 and ch 2 so you know what goes where.

This should get you up and running properly.
<span style='color:blue'>J. Mark Chapman
Crown Application Support Technician</span>

#3 RPMazzi

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Posted 04 October 2006 - 04:58 PM

Nope. I do have the Y with the second input inverted as directed. Any other possibilities?

#4 DGlass

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Posted 09 October 2006 - 09:49 AM

QUOTE(RPMazzi @ Oct 4 2006, 05:58 PM)
Nope. I do have the Y with the second input inverted as directed. Any other possibilities?
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I know it sound kind of stupid to be asking this but..........

Are both of the amplifier's input level controls set to the same level?

Are the speaker leads connected to the Ch1+ and the CH2+ of the amplifier's  banana jacks?

What is the power rating of your speakers?

One other thing to remember is that the 8-ohms rating is the nominal speaker impedance. Impedance is related to frequency. I know of several speakers that at lower frequencies are 6.5 ohms or lower. Put two of these togather and you have a 3-ohm load or lower attached to the output of the amp. In this case the amp would be clipping because it is trying to drive to low an impedance.

In Bridge-Mono mode the output of the amp is what is called floating were both sides of the amp will be sharing 1/2 of the load. So with a load of 4-ohms that could be say 3.5-ohms, at certain frequencies, each side of the amp could be looking at a 1.25-ohm load or lower. sad.gif This would not be a good thing.

#5 RPMazzi

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Posted 10 October 2006 - 04:34 PM

Are both of the amplifier's input level controls set to the same level?
Yes, they are. Both at full.

Are the speaker leads connected to the Ch1+ and the CH2+ of the amplifier's  banana jacks?
Both are going into the positive. The central two jacks.

What is the power rating of your speakers?
The speakers are Avatars. One, a 410NEO, is rated at 1000W. The other, a 115Delta is 500. I know the Delta's power rating is approaching the limit. But I wasnt pushing it very hard at all when the problem was occuring. The pre was only running at half volume and half gain (12 o'clock). The strange thing was the lack of volume. Both speakers were going much louder with the previous amp (Only 400W) with no distortion or break up.