SWR Amplifier POWER 750, Owner'S Manual

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POWER 750 • 5
USING TWO SPEAKER CABINETS
Connect the speaker cables of your choice (1/4" or Speakon) from the speaker out jacks on your Power 750 to the inputs on speaker cabinets.
Can you use one 1/4" output jack and a Speakon output jack at the same time? Yes. Remember, all of the Speaker Outputs are coming off of the
same mono power amp inside the unit.
If the cabinets are the same impedance, the same amount of power will be sent to each enclosure. If the cabinets are different impedances, more
power will flow to the cabinet with the lower impedance. In a mono situation, equal impedances are ideal since there is no individual control over
each cabinet's volume, but there's no law against using cabinets of different impedances, just so long as the total impedance is equal to, or higher
than the amplifier's minimum total impedance (2.6 ohms on the Power 750, or an 8 ohm and a 4 ohm enclosure connected together in parallel).
In plainer terms, this means you can safely use:
a) two 8 ohm cabinets
b) one 8 ohm and one 4 ohm cabinet
c) three 8 ohm cabinets
And you cannot use:
a) one 2 ohm cabinet
b) two 4 ohm cabinets
Again, make sure to check the power handling capabilities and impedances of the speaker cabinets you wish to use against the "Power 750
Specifications" section of the manual.
TURNING THE UNIT ON
Remove the AC cable from the accessory pack and connect it from the amplifier's AC receptacle to a standard wall outlet. Make sure that the
Volume control is set to the minimum position. Locate the power switch on the right side of the front panel and turn the amplifier on. The LED
above the power switch should then illuminate. Upon powering up, don't be surprised if you hear a small pop. This is absolutely normal. (Fully
eliminating this "power on transient" would require a component called a relay. SWR chose not to incorporate this type of component due to the
fact that relays degrade signal quality and often fail, causing the unit to have no output and requiring a trip to a local service center.) This "pop"
can be avoided by having the Speaker On/Off switch in the "OFF" position during powering up.
GETTING SOUND OUT OF THE POWER 750
Plug your instrument cable directly into the unbalanced input jack on the rear of the unit. Make sure the Speaker On/Off switch is in the "ON" posi-
tion. Turn your instrument's volume up to maximum and begin playing. Now turn the Volume control clockwise from minimum slowly toward maxi-
mum. You should now hear the sound of your instrument amplified through the Power 750 into your speaker cabinets. The LED's may not light up
at all, or perhaps only the first (-20 dB) will illuminate. This is normal, as we are bypassing the preamp in this instance simply to determine that
your Power 750 is in fine working order, just as it left the factory.
CONNECTING YOUR PREAMP TO THE POWER 750
Plug your instrument cable into the input of your preamp. Make sure you properly adjust the gain and volume controls of your preamp before
sending the signal to your Power 750. (Check the manual of your preamp for instructions.) Often a preamp will have both a pre-level (usually listed
as "gain") and a post-level (usually listed as "post" or "master"). If the signal is clipping or distorted before it leaves your preamp, it will only get
worse when the Power 750 amplifies that distorted signal.
Once you have achieved proper level settings on your preamp, run a high-quality shielded 1/4" patch cable from the unbalanced output of your
preamp to the unbalanced input on the rear of the Power 750. (The option for a balanced XLR connection exists as well, but we'll discuss that
later.) Make sure the Volume Control on the front of the Power 750 is set to minimum. Set the Speaker On/Off switch to the "ON" position. Begin
playing your bass and slowly turn up the Power 750 Volume Control. Note the Four Segment LED Dot Bar Display as you adjust your level, making
sure to keep the signal out of "constant red." By the time your preamp is sending a healthy signal to the Power 750, and the Power 750 Volume
Control is set so that your hardest notes are just barely illuminating the +3 dB (red) LED on the front panel, chances are you'll be feeling your
insides rumble.
We urge to you to read the remainder of the manual completely and thoroughly for descriptions of all the functions and features on your new
Power 750, as well as detailed operating instructions relating to the power amp and speaker outputs.