Hi guys.

I'm just madly in love with the acoustic tone that John Petrucci's guitar produces.

I've been told that he uses Piezo Pickups on his Musicman.

the question that I have is that can I install these pickups on a guitar that doesn't have this system?

many thanks.
Yes, there are a lot of piezo bridges and saddles that will let you install a piezo on just about any electric you want. The piezo on the JPMM is quite good, so keep in mind that some aftermarket units might be a bit disappointing if that's your standard.
Graphtech Ghosts are pretty great I heard.

You'll probably need an EQ system, maybe an EQ pedal to tweak the sound just right. It's not going to sound exactly like an acoustic for a few reasons.

One is that you're using electric guitar strings which will subtract from the tonality of bronze acoustic strings. You also won't have the body resonance of an acoustic.

Piezos aren't directly meant to sound like an acoustic, but rather have a broad frequency response range which is a lot wider than a magnetic's, which means you're getting practically the naked sound of your strings without any frequency coloring a magnetic pickup would do.
As a result, you get what sounds similar to hearing the strings on your guitar unplugged, because there's no coloring from the magnetic pickups.

This sounds close to an acoustic so many use this as a nice acoustic sound from their electrics, but it still needs to be tweaked by EQ like I said earlier.

I suggest you look at youtube for an approximate demo of what piezo pickups sound like and what they can do for you.
Graph tech ghosts with their preamp is fantastic. The best ones I've heard are the ones on my music man guitars, not just the petrucci models. If you can't install the inboard preamp, a floor type acoustic preamp will do wonders.
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thank you so much guys for your most helpful information.

yes I'm not planing to get 100% acoustic like sound on electric guitar because for that there is something else to buy, an acoustic guitar

I'm just planing to have a different sound from the regular clean sound and all that.

OK so I'm gonna search the youtube for the products you mentioned and also their official website.

and if I faced any questions I will ask again my friends. \m/
Piezos are nice if you want a more pure sound than just a mid-frequency sound that magnetics give you.

Generally people feed it through a PA or acoustic amp, but you don't have to. You can use it anyway you like, it's just that a lot of people use it as an acoustic simulator. It's pretty good as one, but you don't HAVE to treat it like an acoustic. You can feed it through effects and a bunch of other stuff, but the result is debatable.

My newest guitar I got is actually an all piezo guitar, but that's a whole new story in application.