Can i use the pre out straight into a line in on a powered mixer

you always keep your sound in line. what i mean by this is if your powerpod is a PA then you would want to run your instrument-pedals-amp-PA. Not saying this is the only way but it is the standard way to configure your components.

I'm guessing a bit because I don't know exact model numbers, but heres my best guess.
Connect the "pre out" L and R from the Karoake system via 1/4" cables to the 410 unit to line 1 and 2. From there, operate the Sampson unit as if you had two instruments plugged in to it.

It can be a number of things.

Bad ground, excess gain, excess number of mixer channels with no inputs, Make sure the mixer inputs you are going to use are the only ones that are up. Power supply noise- flourescent lighting noise, Clamp on ferrites on the power cords of everything can help reduce this. You can sometimes track the offending source with a battery powered AM/MW radio.

It can also be caused by going from a balanced output to an unbalanced input with some impedance differences.

Effects plug into mixer, mixer plugs into power amp. Others may want the mixer and the effects plugged into the power amp for the most available inputs. (when multiple inputs are available.)

Effects and mixer are a line level output and the mixer can be considered a line level input as well. A mic mixer has gain amplifiers for the inputs that are below line level such as unamplied microphones. It is possible to parse to absurdity, but the gist of it is above assuming you do not want to apply the same effects to everything all at once.

yes,, Pre means before powered or amplified ,, so yes you can do this to a powered mixer, just be sure that the power is off before making any connections,, without the ground of the rca cable touching , the blast to the speakers can invert the cone !!

Either way will work, however your friend's method probably would be slightly better since it goes through less stages within the PMP2000. The "left and right power amp inputs" are the INPUTS to the power amp in the PMP2000 and hence are the best places to connect the mixer if using the PMP2000 as only a power amp. Note doing this will LIKELY disconnect any other input to the PMP2000 from the power amps in it... that is all the preamps in the PMP2000. DO USE TRS cables!!! and power both units from the same receptacle to avoid ground bounce.

The amp takes LINE LEVEL which is in the order of 1 volt or 0 Db... a mic generates only -40DB. You need a preamp or a mixer between the mic and this amp.

If more than one input is bad, then problem has NOTHING to do with the preamps. Check list:
1. Make sure you are using BALANCED lines everywhere... either XLR or TRS cables.

2. Make sure ALL interconnected equipment, mixers, amps, powered speakers, CD players, etc. are ALL powered from the SAME receptacle or power distribution unit.

3. Do proper setup. Select each channel PFL and set the trims so the indicator never goes into clipping, but is in the 70% range during max volume input to mics, etc..

4. During operation the sliders should be at least 50% up on used channels and the mains. Setting of levels throughout the system is important for noise free operation. Using EXCESS gain at some point results in distortion and noise. Using sliders near the bottom position results in poor signal to noise ratio.

Now re-read #2 above... and believe it. I have seen a lot of equipment blown due to ground bounce of building power. That is why the pro's run power back to their mixer from the area where the amps are powered.

Make sure you are using BALANCED line to this... XLR connections boyh ends. Make sure ALL interconnected devices are powered from the same receptacle or power conditioner. Test your cables... they do go bad. This unit REQUIRES line level input. Do NOT expect a mic to drive it directely. Make sure your mixer uses the XLR outputs and is powered from the same receptacle, even if you have to run an extension cord to it. This is a bi-amped speaker so there are independent amps for high and lows. With nothing out and known good in there is very little electronics before the signal is split to the separate amps. At line level, your volume control should probably be about 2 o'clock with the EQ's straight up flat.

In order for this to work properly it must be inserted between the last pre-amp stage and the power amp. Can you please update this with the mixer that you are using? With the make and model of the mixer, I can provide you with a connection description. Since each mixer will have different labeling and options, it is not possible for me to accurately describe the connections without hte make and model.

Thanks,
Dan