maximum amount of amps?

[scampo77]

if I run 4 amplifiers for sub channel and another 4 amplifiers for everything else. Is there a upper limit of amps that a head unit can drive effectivly?

I don't understand if the amps act like a draw forcing more current from the head unit or if the signal voltage is just a signal and doesn't degrade with additional amplifiers.

One more thing, I have about 30 feet of wire between the head unit and amps, Its like a pick up truck and I plan to put the amplifiers in the box of the truck. before I attempt this I was hoping for some feedback.

[VA2GXB]

It's more likely that your alternator is the problem . Usually the input impedance of the amp is high enough to be of little problem

[Einric]

This is why each amp has the gain control on the front.
You will be splitting the sub out in 4 so you will definitely want to tweak those gain knobs.
The same with the main 4ch your head unit most likely has 4 outputs for the main 4 channels, run one to each amp channel.
You will be fine.

[Perry Babin]

The output impedance of the head unit and the input impedance of the amplifiers will determine the amount of degradation of the signal. If the output impedance is flat across the spectrum and the input impedance is flat across the spectrum for the amps, the result will only be a reduction in signal. If the impedance of any of the components is less than flat, it will result in a change in the frequency response.

Some amplifiers have a preamp level output. In some of these amplifiers, the output is simply a pass-thru and is essentially the same as y-cables. In other amps, there is a buffer circuit that drives the preamp output. For these amps, the head unit will see only the first amplifier as a load.

30' of cable shouldn't be a problem but there are a lot of variables.