Crystal Oscillator Noise Suppression

the problem is i am using the same ground for all my components and the Audio circuit is supplied by 24V which also supplies the 5V regulator (linear) for the micro

You should separate the ground tracks for digital and analogue, so that they only meet back at the resevoir capacitor, so that digital return currents are not flowing along the same return path as analogue currents especially near any pre-amp. Digital current spikes flowing in the ground track will cause small vltoges to appear along the track which will be picked up by the pre amp.
I suggest you do some some reading about pcb/circuit layout/interference etc, there is tons of stuff on the web.

If you suspect digital noise is getting back through the 5v regulator onto the 24v than add a couple of ferrite beads and some decent decoupling caps (big electrolytic for lf and small ceramics for hf.) between 24v and the regulator.
(You didn't answer my first Q).
Del

I am still on the placement stage.... i do not want to route the board unless i'm certain about any problems that may occur. Thanks for your answers, they are very helpful.....but the ferrite beads might be too large. I am saving space here...

what if i add inductors between the 24V line and the pre amp?

Ferrite beads are smaller than many inductors so I'm a tad comfused, they can also be slipped over component legs.. although I s'pose you are going all surface mount?
I googled pcb layout tips, there was loads of stuff... try 'ground track laypout' and stuff like that.
Good luck
Del

Ferrite beads can make miracle... I think the source of the noise is not the clock oscillator but the microcontroller itself because the running program "divides" the clock frequency according the number of clock cycles necessary for the execution of the machine instructions or program loops. Decoupling will be necessary, with tantalum capacitors soldered directly to the power legs of the controller and ferrite beads. You also can interrupt the 5 V line leading to the controller and insert a small inductance.

Consider adding a 1 Ohm resistor in series with the +dc supply to the analogue part of the circuit with a large value capacitor between this resistor and the dc return path on the circuit side of the resistor. The voltage drop across the resistor will probably not worry the analogue circuitry, but the presence of the resistor will make the capacitor much more effective at removing noise. If the current drawn is low enough to allow you to make the resistor larger the noise reduction will be even better. If you allow for the resistor in your layout you can always replace it with a zero ohm link if it turns out you don't need it later.