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Author Topic: Help With Set-up - dBx DriveRack 260 and JBL  (Read 12574 times)

Tim McCulloch

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Re: Help With Set-up - dBx DriveRack 260 and JBL
« Reply #10 on: August 01, 2011, 09:06:26 am »

No. In bridge mode, both inputs of an audio amplifier are in use. Input 1 is paralleled into input 2 and the polarity is inverted into input 2 as well.

EDIT

Perhaps I was a bit hasty. I suppose that the amp to amp signal jumpers could also be polarity inverted, returning the polarity to normal as the signal enters input 1 of the second amplifier....but this starts to complicate the signal wiring scheme of the amp rack.


No.  Don't even try this.  It will put reversed-polarity cables into inventory that will inevitably get mixed in with others, creating a bunch of hard to find problems later.  It's also possible that in bridge mode that the ch. 2 XLR doesn't "see" the inverted polarity signal anyway.  No output means no worky down the line.

Better would the to make up some spade lug to XLR cables.  The barrier strip inputs on the CE4000 are wired with the XLR connectors.  Use the ch. 1 XLR input of the first amp, then use the spade lug to XLR cable, wired to ch. 1 on the barrier stip, to jump to the next amp.  No confusion, and if one wants the amps separated for a different configuration, it's as simple as unplugging the jumper.

Have fun, good luck.

Tim Mc


Hmmm...ok.  Are there instances where two processors (DriveRacks) are used (one in each rack for right and left stacks fed left and right from FOH) with the same exact settings?  One of my racks is configured (with DriveRack 260) for a small set-up of SRX 715's and SRX 718's which I use for most of my gigs.


I don't understand your reply to me or how it fits the quoted texts.

My point is this:  the "inverted" ch. 2 signal may or may not be present at the ch. 2 XLR *input* jack; if it is, then building a bunch of XLR male-to-male, swapped polarity cables isn't a good idea (although one could argue the M/M nature would limit how they'd be used).    The spade lug to XLR is simple, neat, and leads to no confusion.  This has zero to do with using a processor for each side of the stage.

I'm also a bit surprised the CE4000s have held up driving a 4 ohm load in bridge mode.... I'm glad you haven't experienced any issues.

Have fun, good luck.

Tim Mc


Tim, don't get me wrong, I am "listening" to everything that you have stated.  I just have all sorts of thoughts about alternative solutions.

If possible, could you show some sort of diagram of these jumper cables? 

The CE4000's have worked very well for me and I hope they continue to do so until I can afford some better gear.  I believe that they faired well in an amp shoot-out some time ago.

The CE4000 is far more robust (and a different design) than the other amps in the CE series and it's a pretty good amp for it's day.  I'm not bashing the product; I think we still have 14 of them... but they weren't designed to do 4 ohm bridged operation.  That yours have given you no trouble is a good thing, but don't be surprised if you eventually have failures that will require sending them back to Crown for service.

The XLR jumper is just that... take a 12" length of WestPenn 291 (or equal)... it's 2 conductor twisted pair with a shield drain wire.  Solder the drain wire to pin 1, white to pin 2, black to pin 3.   On the other end of that 12" length, crimp a spade lug to each wire.  Hook them up to the ch. 1 screws on the barrier strip, drain to the "ground", white to "+" and black to "-".  It's really that simple.  This gives you the channel 1 signal at the XLR, and you can just plug it into the next amp.  No next amp?  Don't plug it in, it won't hurt anything in 99.9% of circumstances (extreme RF environment might be an exception).

Sometimes you need to think "clever" rather than "overthink."

Work smart, not hard.

Tim Mc
« Last Edit: August 01, 2011, 09:08:15 am by Tim McCulloch »
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Rufus G. Crowder

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Re: Help With Set-up - dBx DriveRack 260 and JBL
« Reply #11 on: August 01, 2011, 12:59:27 pm »

No. In bridge mode, both inputs of an audio amplifier are in use. Input 1 is paralleled into input 2 and the polarity is inverted into input 2 as well.

EDIT

Perhaps I was a bit hasty. I suppose that the amp to amp signal jumpers could also be polarity inverted, returning the polarity to normal as the signal enters input 1 of the second amplifier....but this starts to complicate the signal wiring scheme of the amp rack.


No.  Don't even try this.  It will put reversed-polarity cables into inventory that will inevitably get mixed in with others, creating a bunch of hard to find problems later.  It's also possible that in bridge mode that the ch. 2 XLR doesn't "see" the inverted polarity signal anyway.  No output means no worky down the line.

Better would the to make up some spade lug to XLR cables.  The barrier strip inputs on the CE4000 are wired with the XLR connectors.  Use the ch. 1 XLR input of the first amp, then use the spade lug to XLR cable, wired to ch. 1 on the barrier stip, to jump to the next amp.  No confusion, and if one wants the amps separated for a different configuration, it's as simple as unplugging the jumper.

Have fun, good luck.

Tim Mc


Hmmm...ok.  Are there instances where two processors (DriveRacks) are used (one in each rack for right and left stacks fed left and right from FOH) with the same exact settings?  One of my racks is configured (with DriveRack 260) for a small set-up of SRX 715's and SRX 718's which I use for most of my gigs.


I don't understand your reply to me or how it fits the quoted texts.

My point is this:  the "inverted" ch. 2 signal may or may not be present at the ch. 2 XLR *input* jack; if it is, then building a bunch of XLR male-to-male, swapped polarity cables isn't a good idea (although one could argue the M/M nature would limit how they'd be used).    The spade lug to XLR is simple, neat, and leads to no confusion.  This has zero to do with using a processor for each side of the stage.

I'm also a bit surprised the CE4000s have held up driving a 4 ohm load in bridge mode.... I'm glad you haven't experienced any issues.

Have fun, good luck.

Tim Mc


Tim, don't get me wrong, I am "listening" to everything that you have stated.  I just have all sorts of thoughts about alternative solutions.

If possible, could you show some sort of diagram of these jumper cables? 

The CE4000's have worked very well for me and I hope they continue to do so until I can afford some better gear.  I believe that they faired well in an amp shoot-out some time ago.

The CE4000 is far more robust (and a different design) than the other amps in the CE series and it's a pretty good amp for it's day.  I'm not bashing the product; I think we still have 14 of them... but they weren't designed to do 4 ohm bridged operation.  That yours have given you no trouble is a good thing, but don't be surprised if you eventually have failures that will require sending them back to Crown for service.

The XLR jumper is just that... take a 12" length of WestPenn 291 (or equal)... it's 2 conductor twisted pair with a shield drain wire.  Solder the drain wire to pin 1, white to pin 2, black to pin 3.   On the other end of that 12" length, crimp a spade lug to each wire.  Hook them up to the ch. 1 screws on the barrier strip, drain to the "ground", white to "+" and black to "-".  It's really that simple.  This gives you the channel 1 signal at the XLR, and you can just plug it into the next amp.  No next amp?  Don't plug it in, it won't hurt anything in 99.9% of circumstances (extreme RF environment might be an exception).

Sometimes you need to think "clever" rather than "overthink."

Work smart, not hard.

Tim Mc

Sure thing and thanks... I will work on this tonight!
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Re: Help With Set-up - dBx DriveRack 260 and JBL
« Reply #11 on: August 01, 2011, 12:59:27 pm »


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