Hiwatt Pereira clean - Please use a Compreseeur +   Boost before amp 
 
Hiwatt Tube Driver - Compresseur  +  Silicon Overdrive Before to Amp - low drive is enought to push amp capture to the Real Tube Driver Experience 
 
Hiwatt G2 Mode  - Compresseur +  Boost before the amp is advise - EP boost type - do not use overdrive otherwise you will lose the quality Signal
Hiwatt P1 Mode - compresseur + Boost before the amp + EQ with slight high end and low end cut keeping mids on level you need according to your guitar