PLX Series User Manual
Rear Panel
12. Cooling fan
18. Parallel/Stereo/Bridge mode switch
13. Parallel signal outputs
19. Speaker outputs 1 and 2
14. Signal inputs
20. 4mm binding post speaker outputs (inc. Bridge)
15. Ground lift switch
21. IEC mains inlet
16. Compress (clip limiter) switch
22. Mains fuse holder
17. Input sensitivity switch
23. Cooling fan
Operation
Connect speaker cabinets to channel outputs using good quality leads via the SPK connector or binding posts and ensure
that the combined load on each channel is no lower than 2Ω.
For speaker loads connected in parallel…
1/speaker imp 1/speaker impedance… = 1/TOTAL impedance
Therefore…
8Ω + 8Ω = 4Ω total
4Ω + 4Ω = 2Ω total
8Ω + 8Ω + 8Ω + 8Ω = 2Ω total
Both channels can be used to drive a single load at the combined volume of each by switching to BRIDGE mode. In this
mode, the input is on channel 1 and output from CH1 SPK connecter (pins 1+ and 2-) or across the red “+” terminals as
indicated on the rear panel - WARNING - Minimum load for bridge mode is 4Ω
Connect each signal input from mixer or other line level source via the XLR connectors on the rear panel using good
quality signal leads. Depending on output level of the mixer, select the appropriate sensitivity on the rear panel.
For protection in high power situations, the onboard COMPRESS function may be switched in to protect from overload.
In situations with excessive mains hum coming through the speakers, it may help to switch the GROUND to the LIFT
position. This is may help in some situations but otherwise, it is preferred to be switched to GND.
XLR inputs and outputs for each channel are wired in parallel, allowing signal to be carried forward to further amplifiers.
Connect the amplifier to a mains outlet, ensuring that the IEC lead is earthed, in good condition and connected securely.
With channel gain controls turned fully down, switch on the power to the amplifier. This unit has a “soft-start” function
which makes some checks before engaging power to the amplifiers, which may take a few seconds.
With mixer (or other signal source) levels turned down, gradually increase the amplifier’s channel level controls to the
required level (normally full) and then gradually increase the signal level from the mixer or sound source until sound can
be heard through the speakers and then continue increasing up to the required level.
During use, green “SIGNAL” LEDs will illuminate to show when a signal is present and yellow “CLIP” LEDs illuminate if the
output is reaching clip level. If the red CLIP LEDs illuminate more than very briefly, reduce the volume until they hardly
light up at all.
If the internal protection circuitry detects a fault in the speakers or amp, the channel(s) will enter Protect Mode and red
“PROTECT” LEDs will illuminate on the front panel to show this. Switch the amplifier off and check the entire system
(including leads) before powering up again. If still in Protect Mode, seek advice from qualified service personnel.
Before powering down, turn the channel gain controls fully down to avoid loud noises when switching off.
