A clone of the Hornby Skewes Treble Booster with original Mullard/Philips OC75 loaded circuit on cloned PCB amp-top treble boost in the same vein as the Rangemaster.
Favoured by Ritchie Blackmore (Deep purple) the circuit later found its way into the Hornby Skewes Shatterbox as the boost section used by Marc Bolan.
