[Eeyore]

thanks wrote:

If I have a 24 Volts DC
regulated stabilized output low
ripple but switching power supply

Can I use that for a microphone
preamplifier module which
requires 24VDC for operation?

Yes. It will work.

Or must it be linear or I will
damage the unit?

No and no.

Depending how well the mic pre was designed it may or may not benefit more or
less from a linear supply with even lower output noise. You omitted to mention
the actuall ripple and noise voltage ( and measuring bandwidth ) from the
switcher.

Graham