Does the length of the Cable matter?

"Length  always matters"

....what she said. 

@erik_squires

Technics 1500 with built-in pre so it’s fine.

@jjbeason14 

Since the preamp is built in to your TT, you should be fine.

All the best.

Unless I’m mistaken, the input impedance of your phono preamp is 47,000 Ohms. This means an increase in impedance from a long length makes no difference.

Shielding is the next thing. I have a 1.5m length phono cable. If that shielded phono cable crosses a power cord, I get a slight hum. Therefore make sure your long phono cable doesn’t get too close to a power cable.

The 15’ of cable would definitely be a mistake if your turnable is 16’ feet away from the phono stage.  Otherwise, you should be fine.