thats true and it is fact we can recreate many things today internal the box like hardware but to increase the quality of your sound you should buy at least one good preamp. you do not have to spend thousand of dollars for this but good quality signals are important for the internal mix down.
it is a fact of physics you cant recreate frequency's which not have been recorded.
for this fact a good microphone and a good preamp as well as a good-mic-cable is necessary.
What platform is he using? Cubase? Logic? Pro Tools?
There are many preamp plugins, some do their job, some don't.
In my experience I liked what I heard with:
AM-Phibia by Magix
And LM-662 by Nomad Factory
Waves SSL Channel
But to get the optimum quality, your friend has to have a transparent frontend (soundcard & A/D converters) to his PC in order to keep the signal as close to original as possible (If your friend is plugging to his $50 soundcard, tell him not to botherheh )
Even after that, some will say that the sound is not comparable to real gear, but with some creative tweaking, those plugins can save the day.
It is impossible to have a plug-in act as a mic-pre because in order to get the signal into the computer you have to go through a converter which accepts line level inputs and outputs that line level signal to digital. How are you possibly going to amplify a mic-level signal when you have no mic-level signal to amplify? Plus, the amount of signal going into the converter would be so low and noisy you'd never want to use it in a recording.
Other "plug-in amplification" software that is available is really just a modeling of gain on a pre-recorded signal. You can model EQ, Compression, Reverb, etc. but if you are going to be using microphones, you absolutely have to have a mic-pre to get that signal into your converter and thus into your computer.
My forthcoming EQ update contains a pre-amp stage simulation which covers some non-linearities like transformer bass distortion, tube harmonics, freq&phase response etc.
Some more info on my blog here and here.
PC / VST only.
A microphone preamp (microphone pre-amplifier), most commonly called mic preamp, is a device used to amplify the voltage taken from a microphone to a higher, more usable level. Most microphones must be used in conjunction with a microphone preamp to function properly.
Now how the fukk are you going to get a plugin to do that..??