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About Pignouf

  1. Hello, I have a little question about the XLS series amps. Well it's a little embarassing, but actually it's about the GB series amps from C-Audio, which was a sister company of Crown which stopped production some years ago. You see, a friend of mine bought himself some GB amps (one of each : a 202, a 402 and a 602), but he knows nothing about how to connect everything. I myself owned some XLS 602's (the 3U's) some years ago, and when he showed me the GB amps, the resemblance was obvious. After some searching I found out that C-Audio was a sister company of Crown, and seeing that the amps where practically identical, it's fairly normal I assumed Crown took over some models and rebadged them (and looking at the discontinued models of Crown, I also see the Pulse series, which was also a C-audio product line, I'm pretty sure of that now). C-Audio not longer exists, so I thought if anyone could help me, it would be the guys at Crown. Lemme explain the situation : my friend has a JBL sub (Marquis series if I remember well) and two JBL tops (that I don't remember the model of). So = mono sub, two tops. The guy that sold him the amps told him the idea was to use the 602 in bridged mono mode to power the sub, and link the 602 to the 402 which has a AMPSAP crossover card installed. The problems I have with that are multiple. 1) the guy told him to enter a stereo input in the 602 (so L and R from the mixer), and connect the sub using the red terminal of channel 1 and the black terminal of channel 2! Which I seriously think is a load of bullsh**. The GB602 is similar to the 3U XLS602, it has no bridge switch. I've always assumed that the way to bridge "old style amps" was to send the same signal to input 1 & 2, but with one side phase inverted (by making a custom Y cable). The terminals you should be using are the two red ones. Am I right? Meaning that if he uses the male XLR outputs (the thru's in other words) to link the 402, he would be sending a mono signal (with one side inverted) to the 402... But if we sent a "normal" stereo signal to the 602 (different signals between channel 1 & 2), wouldn't that be detrimental to the bridging? 2) So assuming that we send a "normal" stereo signal through the 602 like that guy said. That brings me to that AMPSAP thingy. The only thing I have found about it is that it means Advanced Multitasking Primary Signal Access Port, and that it's an expansion port available on the GB amps, and apparently on some of the Crown XLS 3U amps (it''s mentioned in the XLS 3U circuit description and service notes). Although I don't remember seeing an expansion slots on my 602's (it's been some years since I sold them, so I might completely forgotten about them). Well, his GB402 has that expansion card filled with a crossover card. It has 4 XLR outputs. I assume 2x LF + 2x HF. But what I don't know is where it taps it signal. Reading the service notes it seems that it's an active design. But wouldn't that mean its outputs should be connected to amps? I asked my friend if he could remove the card and see how it connected to the amp, and apparently it connects through flat cables (like old PATA harddrive cables) to the amp PCB. It would surprise me that a full amplified signal would be sent through such small wires... 3) Even then, in my humble opinion, the crossover would be at the wrong place. I mean he would send an unfiltered signal to the sub, and only a highpass filtered signal to the tops. Wouldn't it be more logical to have a x-over before both amps? Seriously, unless I completely misunderstand the working of the amp with the x-over card, I feel the guy that sold him the gear told him pretty weird things. I told my friend that personally, I would get a stereo 2-way crossover, put it between the mixer and the amps. He could then take the LF output (summed to mono), do the bridge mono trick (Y cable inverting one side) on the 602 and take the HF output to the 402. Is my reasoning right? Or is there something I'm missing here? Thanks in advance, P.