Bridging QSC PLX question

[newchibass]

I have a new PLX 1602 being delivered to me today. This is my first journey into a power/pre setup and I had a few questions: 1) I will be initially bridging this into a Acme B2 (4 ohms) with 1/4 inputs. Do I need speakon connectors (from the amp) in order to do this? If I don't need to should I anyway in terms of ease of use or sound quality? Thanks.

 

[Bob Lee (QSC)]

The amp has both Speakon and binding post output connectors. Pages 16 and 17 of the manual show pictorially everything there is to know about how to use either type for bridged mono.

 

[Big String]

There are a lot of post on this subject. Do a search.
If you are unsure how to hook it up...carefully read the manual it's well written. Your best bet, since you're new at it, is to use a Banana Plug going to the back of the amp and a normally wired speakon connector going to the Acme cab.

You MUST have the dip switches on the back of the amp set correctly and then use both RED OUTPUTS on the back of the PLX to correctly BRIDGE. If you make up a cable make sure the + and - are correctly connected on the speakon.

You would then take the NEG (-) Black banana plug to the RED Channel TWO and the POSITIVE (+) RED banana plug to the RED Channel ONE. That way your are "BRIDGING" the two power sections of the PLX.

LOOK over your manual and understand what you're doing first. You can really mess up your gear if you don't and get a horrilbe shock too....

Once you have it properly bridged, be careful how you start running it. Take it easy first and remember there is BOOKOO current runnning through the cables. You benefit is gaining "headroom" by bridging your amp meaning you have more clean power. Watch your clip light on the front they tell you if you're sending too much to the cab and over taxing your amp.

Also, with a PLX when Bridged you only turn up the gain control on Channel ONE leave Channel Two completer off as Ch 1 is the MAIN on this amp. Good Luck and have fun.

 

[Bob Lee (QSC)]

Also, with a PLX when Bridged you only turn up the gain control on Channel ONE leave Channel Two completer off as Ch 1 is the MAIN on this amp. Good Luck and have fun.

On a PLX amp, channel 2's gain control is completely out of the circuit, and its setting doesn't matter. Everything else you wrote was right on target!

 

[newchibass]

Thanks for the info!

Mike

 

[Big String]

Ahhh, thanks Bob. Is that an improvement or was it always like that? I seemed to remember some advise as to making sure Ch2 was off all the way when Bridging.

 

[Bob Lee (QSC)]

That's with the RMX amps. The internal signal routing for bridged operation is a bit primitive compared to the PLX and PowerLight amps, but that's also one of the reasons they cost less.

 

[alexclaber]

One more point - don't feel you have to turn the gain controls on the PLX all the way up. You still get all the headroom and power with the volume knobs down low, it just takes a higher voltage from the preamp to max out the power amp. When I started off using my PLX 3002, running the channels in parallel @ 4 ohms (=900W RMS) into a pair of Low-B2s, I had the knobs all the way up because I wanted to make sure I got every ounce of power. Totally unnecessary and just asking for something to go back when you step on the wrong effect pedal or unplug your bass without thinking.

I now generally keep the gain controls at 12 o'clock, which is sufficient gain to really push the Acmes with an SWR Grand Prix driving the PLX.

Alex