The only reason to purchase a Sonos Amp would be to drive other speakers. 

Do you have the Beam and the Fives set up as two rooms, or are they bonded together so that the Fives function as surround speakers for the Beam?
 

The difference here is that when set up as surround speakers, the line in on the Fives is turned off. If you’re using them as a separate room, the line in would be active, and you’d just need to put a pre-amp between the turntable and the Fives, and you would be able to listen to the turntable. 

They can, if you are on S2.  What makes you think they can’t?

I have both sonos 5 on stereo and the beam together but the sound is no good when I’m using the turn-blade.

Dont know how to explain, it’s like you getting a satured sound, like the sound coming from a box and I need to have the sound on 55 minimum on the app to get something .

Would be better with the Sonos amp? I was thinking maybe is because you can’t connect the  beam with both 5 together 

It sounds like you have the pre-amp turned off.  There may be a switch on your turntable that you currently have set to PHONO.  You need to set this to LINE.

The switch is on the rear of the unit.

Hi,

I just checked and I’m on LINE on my turntable . My turntable is connected to one of my Sonos 5.

My set up is good and I’m getting a very bad sound.
Im not getting this problem when I’m using the TV. 

What is the line-in level set to in the settings for the Five?  if it is low, increase it to 9 or 10.

Thank you, the setting was put it to 1

would be a great idea to buy a Sonos Sub to my system? 
Watching a lot the TV and enjoying my vinyls

I have added big Subs to all the rooms I listen to a lot.

Might look into a mini-sub for a smaller room that only has Play 3s depending on how it sounds from posts here.

Thank you for all yours answers
I will buy one

Good news! I'm glad you have got it working properly now.