bent wrote:

I don't notice any different when i record it in 4 tracks at the same time except its louder

If it just sounds louder then you want to move the mics around a bit, space them out, flip the phase on one or two,

What do you mean by Phase ?

Phase, Entry 3 from Webster's Dictionary:

The point or stage in a period of uniform circular motion, harmonic motion, or the periodic changes of any magnitude varying according to a simple harmonic law to which the rotation, oscillation, or variation has advanced from its standard position or assumed instant of starting.

Simply put:
Audio signals that are in phase are additive - their amplitude increases.

Signals that are 180 degreees out of phase cancel each other - their amplitude is nullified.

Pictures-
In phase: http://en.wikipedia.org/wiki/Image:Sine_waves_same_phase.svg

Out of phase: http://en.wikipedia.org/wiki/Image:Sine_waves_different_phase.svg

So with mic placement whats makes it out of phase? the position placement over the cone of the amp ??

There are many factors involved.

One of the most prevalent is distance (two mics, single source).

Example: Mic'ing the top and bottom of a snare drum will almost certainly adversely affect the phase relationship of both signals.

The single source (the snare drum) enters the microphones at a slightly different time which in effect puts them out of phase. This in turn causes a lessening of certain frequencies resulting in a thinner sound. Flipping the phase, or changing the distance between the mics fixes the problem.

This isn't a perfect definition, being that the two signals do not entirely cancel each other out, but I think you can visualize what I'm saying.

could you not just copy and paste an already recorded track to amplify it ? cos they would be definitely in phase ?

No, that would be redundant.

The purpose of using two mics is to add 'flavor' to the sound (Snare top mic picks up the attack of the stick hitting the skin, bottom mic picks up the snares underneath, mix to taste).

Analogy:

Copying and pasting the same track is akin to trying to make a new chocolate ice cream flavor by combining two scoops of the exact same chocolate ice cream, you'd just end up with twice as much...

Edit> This is probably a good time to explain what ADT (Auto. Double Tracking) is?

So why do people record the same riff twice sometimes with same guitar/mic/amp cos that would mean that is also the same ice cream flavor as the first take cos they have not changed the tone sound ?

No, they do it because nobody can play exactly the same thing twice - which I feel is soon going to lead us into a discussion of ADT, as mentioned above...

I don't normally cut and paste, but this is as good of a definition as I could give, and it saves my fingers for other things...

Artificial (or Automated) Double Tracking or ADT)

A technique that creates two tracks of a recorded signal using only one actual recording. Double tracking has been a common studio practice for many years, most often utilized to create a fuller, "fatter" sound on lead vocals. The technique was simple: the vocalist would record his or her part twice. When the two versions were played back together, the minor variations in pitch, inflection, and timing would result in a uniquely thicker sound. In a technological advance attributed to recording engineer Ken Townshend during a Beatles session, a recorded vocal track was re-recorded onto a separate machine that had been modified with a variable oscillator, causing the tape speed (and therefore the pitch) to fluctuate slightly up and down. This modulated signal was then fed back into the first machine to be combined with the original signal, emulating a double-tracked vocal. This technique was also widely used on guitar and other instrumental tracks. Artificial double tracking can now be achieved electronically through the use of delay and pitch-shift circuitry or plug-ins.