Can i go straight out of the pre out on my fender frontman into a powered mixer pa system

The Pre Out and PWR In for a method to insert an effects loop. The output signal from the Pre Out should be line level so you would not connect this to our microphone input on the PA, but preferably to a Line Level input otherwise you would overdrive the PA's input. When you connect the Pre Out, the 1/4" jack may interrupt the signal so you may lose output to the Champion's amplifier/speaker. If this happens, you need to have a return line with the same line level signal plugged into the AMP In to get your sound back on the amplifier itself.

If this is an XLR style plug it is most likely a control port for something like an external mixer or effects box.

PRE OUT/PWR IN - (1) Effects Loop - Connect PRE OUT to an effects device input, then connect the effects device output to PWR IN. (2) Multiple Amps - Connect the primary unit's PRE OUT to the auxiliary unit's PWR IN. The primary unit is used to control all auxiliary units. (3) Recording or Reinforcement - Connect PRE OUT to sound equipment's input. Both jacks use a TS (Tip-Sleeve) standard type plug for connections. PRE OUT includes onboard tone shaping.

Simple: connect the headphones out (3.5mm jack) to the input jack of your fender (6.3 jack). By doing this you will loose one channel so you better generate a mono signal inside your computer before. Electrically this is no problem, nothing will be damaged. Turn the gain and volume knobs down and apply a signal from your Mac. Gently increase gain and volume. Et voila wonderful mono sound through a guitar amp

You should be able to SAFELY IF both the mixer and the Fender are powered from the same receptacle or power conditioning module. Keep the cable short <10 feet OR convert to balanced lines for long runs and then of course run power alongside the run so the units are powered from the same receptacle.

The power amp input jack takes "line level" input BUT is monaural (single channel). The output of an ipod is Stereo. Hence you would have to "mix" the two channels before connecting to the Fender. Mixing does NOT mean just tying the two channels together. A minimu thing would be a passive resistive mixer consisting of a resistor from each of the IPOD channels to the common point going to the input of the Fender. Remember if you plug into the Fender power amp input you DISCONNECT the preamp and other circuits and would ONLY hear the IPOD input.

Hum is always connected with the presence of AC interference into the signal path of the amplifier, which means the audio amplification is mixed with the ac ripples.
So this can be a break down with the power supply as a possible tank capacitor or a stabilizing capacitor in the main power or the sub sections of the amplifier or pre- amplifier.

No, when you plug into the power amp in that disconnects the feed-through of the preamp.

If one choses to use an external amplifier one takes the pre out and connects that to the in of the external amp.

If one uses an external mixer and wants to use the amp and speakers in the cabinet, the output of the mixer is connected to the Power Amp input.

HINT: DO NOT use these jacks... the jacks have switch contacts that pass the preamp to the power amp and if you use the jacks, sometimes these contacts fail and then you have to open the amp and restore the contacts to get it to work.

The jacks are really weak and EASILY damaged as are the guitar inout jacks if the cables are yanked sideways.

ALWAYS loop your cables through the handle so if they are yanked they don't damage the jacks.

If you ran from the speaker out to the direct box you may have damaged your output stage on the amp and the direct box. The best way is from a line out, recording out if your amp has one. Ann alternate way is from your headphone out if your amp has one.