Hi there,
 
I'm using Sonar X1 Essential and I've started to record live piano from my Roland FP 50 via my focusrite 6i6 interface into my DAW. Unfortunately there is this Shh white noise sound behind the audio which is not really noticeable until I normalise the audio and then it becomes deafening. When I record into Sonar the signal is very weak and the waves are tiny which is why I have to normalise to make things look semi normal! Any thoughts on how to sort this out wold be greatly appreciated! ( PS I would like to include some screenshots of my audio settings but when I want to attach an image it wants a URL?.....)

You are probably amplifying the random electrical noise in your analog recording chain. You need to adjust the recording gain/volume in your audio interface. There is no way to increase the volume in Sonar if the signal delivered by the interface is too low without increasing the noise. In your case it is bringing the noise floor up to audible range. 

Hi thanks so much for your swift reply! I'm a novice so I don't understand what you mean by analogue recording chain? Is that the signal into my daw? The gain volume is half way up on my interface - so does that need to be all the way up?

How are you connecting the piano to the interface? 
 
Your analog chain begins with the audio 1/4 inch output jack* of the piano or speakers if you are using a microphone to record the sound output from the piano and continues into your audio interface until it hits the analog to digital conversion stage in the interface. Once the signal is converted to digital (which is all that Sonar receives) there is no way to increase the signal relative to the noise. 
 
If the output from the piano is not sufficient then you need to increase the gain on the interface. If the output volume control on the piano is not set high enough then just increasing the gain in the interface will also result in recording electrical noise at a high ratio to the audio signal. 
 
*Actually the analog chain includes the internal electronics inside the piano as well--so everything after the digital to analog convertors inside the piano that produce an electrical audio signal that feeds the piano speakers or the analog output jacks. 

I'm connecting it via jacks. The output volume control from the piano is also set half way. So I'll put it on max as well as the gain on the interface?

you may(likely) experience clipping if you max both the piano and the interface....maybe 3/4 on the piano to start then move the interface up to 3/4 as well and slowly go up from there testing along the way.

whats the piano model and interface ??
 

Probably not. 
 
You need to adjust the levels to the optimum for what you are playing. Too low gives you the problem you are having, too high causes digital distortion as you overload the capacity of your digital signal to record changes in level aka clipping. If you have the X1 reference guide, the proper adjustment is explained in tutorial #3 pp 114 ff.
 
https://www.cakewalk.com/Support/Knowledge-Base/2007013228/SONAR-X1-Documentation
https://www.cakewalk.com/Support/Knowledge-Base/2005260/Audio-Tutorial-setup-Record-Playback
 

okay will do! It's a Roland FP 50 and a focusrite 6i6 interface 

Aaah thank you I see that according to the manual my levels are definitely too low