can I run an FA-1 clone at 18V?

[dhinca]

Hi Folks, I'm planning a simple practice amp using Aion prism (FA-1 clone) as the preamp, and Vellman K4001 (TDA2003-based) power amp.  I intend to use an old PC 18.5V adaptor, which looks to have enough juice for the power amp.  Will this cause a bias problem for the 2SK246 FET at the front end of the FA-1?  If so, should I change gate and/or source resistor values?  or just set up a 9V regulator for this?  I don't foresee an issue with the opamp (using NE5532, or possible 4558).
Schematic from Aion site: https://www.dropbox.com/s/2plnxj50nxqchxk/aion-prism-fa1-documentation.pdf?dl=1

Separate issue, I read that TDA2003 amps don't like large input values (so maybe overkill to use the FA-1).  I intend to use a 50kA volume pot at the input of the amp (sort of like master volume).  I read somewhere about using diodes to limit the input there, but doesn't make sense to me if I want to keep signal clean... any clarification appreciated!
Thanks!

[vigilante397]

You'll definitely notice some increased clean headroom, but I don't see any reason it shouldn't work. The datasheet says it's good up to 50V between Drain and Gate, so it should be fine.

[Kipper4]

Just make sure the caps are rated for the higher voltage.

[dhinca]

Roger that.  Yep, caps all well above 18V rating.  Thx.