Bass amp introduced in 2008. Most likely the original name for the King's Head must have been Big Ben, as the name Big Ben can be found on the stickers on top of the Mercury Magnetic transformers (picture below) and the power transformer datasheet from Mercury Magnetics (which you can download below). For some reason the name has changed to King's Head by the time they came into production. There are only a few King's Head bass amps made by 65 Amps.
The "Deep" switch on the frontpanel changes the midrange resistors that are connected to the bass. Just shifts the mid notch relative to the bass.
The "Boost" switch on the frontpanel is a boost by adding bypass caps to the cathodes of a preamp tube.
The "Smooth/Grit" switch on the backpanel is like the "Bump" switch on other 65Amps and adds some diodes that smooth out the crossover notch on the output tubes.
The "Choke Pre/Post" switch on the backpanel makes it possible to have the plate supply voltage fed post choke (instead of directly after the primary filter cap before the choke). The post choke setting gives the power tubes a softer attack and slightly less total power.
Output power: 150 Watt
Pre-amp tubes: 3 x 12AX7
Power tubes: 4 x 6550
Rectifier: Solid state
Frontpanel controls: ON/OFF, Standby, Presence, Bass, Midrange, Treble, Volume, Deep switch, Boost switch
Backpanel controls: Smooth/Grit switch, Choke Pre/Post switch, 4Ω & 8Ω impedance switch
Head: 24.75" W x 8.75" D x 10.50" H, Weight: 47 lbs
List Price back in the days (2008):
Head - $3,800