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Bridging a stereo input?


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#1 ProDJ

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Posted 13 September 2005 - 04:56 PM

The system is as follows:

A DBX 234XL takes 2 signals (stereo) and makes 6 signals (Left and right highs, left and right mids, and left and right lows).  I am trying to sum my lows together and bridge that signal in a CL1 or K1 amp to drive my subwoofer (JBL 4642A).  How should I do this?  Do I need a separate op-amp summer or is this stereo-bridging circuitry built into these Crown amps?

The explanation of the Y-input for the K1 is unclear to me.  The CL1 does not appear to have this circuitry.

Please ask for explanation if my question is unclear.  Thanks for the help.

#2 DGlass

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Posted 14 September 2005 - 11:21 AM

I'm not clear what you are trying to fully accomplish. I get the part about combining the low signals together, and will address that below, but are you also looking to put the amplifier in Bridge-Mono mode or send the combined signal to both input of the amp using it in Two Channel Mode?

The "Y" input selector, on the K-2 switch does exactly as its name describes it "Y's" the inputs together so the two input connectors are jumpered together and both inputs get the same signal. This could be used just like having a "Y" cable on the input connectors. One input to the "Y" connector could feed signal to both amplifier inputs. Since the switch combines both input connectors it could also be used to combine the two input signals and feed this combined signal to both channels simultaneously.

The CL series does not have the "Y" switch feature. To do the same thing on a CL series amplifier you would need to put jumper wires between the ch1 + and ch2+ input screw terminals and the ch1 - and ch2 - screw terminals.

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Amplifier Bride-Mono is a completely different thing. Amplifier Bridge-Mono combines the two output stages of an amplifier and makes it a larger Mono amplifier were one side of the amplifier is being driven high (positive) while the other side is being driven low (negative) the same amount.

In amplifiers that have a Bridge-Mono switch the switch routes the input signal from channel 1 to channel 2 bypassing the channel 2 input level control and only uses the channel 1 level control. The signal polarity is then reversed before being fed to the channel 2 side of the amplifier.

When an amplifier is in Bridge-Mono mode the speakers are connected across the positive output leads for channel 1 and channel 2. If you measured the output voltage between the two positive outputs you would have twice the voltage output because you are referencing the negative to an output side that is changing, with the signal, exactly opposite of the side that is pushing the signal.

Using the Y switch on the K series when it is switched to Bridge-Mono would allow two input signals to be combined together and fed to the channel 1 input.

I would recommend that you also check with dbx to see if they recommend putting a Y on two of their outputs for combining signals together.

#3 ProDJ

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Posted 14 September 2005 - 01:33 PM

I checked out the 234XL and it has a switch that sums the low frequencies.  Problem solved.

Thanks for the help!