How do make a Tubescreamer style drive more... djentlemanly? Leave it to Misha Barton, apparently. The 'attack' knob is a 6-way rotary switch that moves the midrange hump, and it's got more gain range and a powerful brightness control, plus a noisegate in there. Thanks Misha, you done good. 

Model: Horizon Devices Precision Drive
Made in: USA, recent model (serial AC63D014)
Type: overdrive/preamp, Dumble voicing
Power: standard 9v DC negative supply (not included)
Equivalent new street price (approx): $349aud
Mods: none
Accessories: original box and manual
Condition notes: used, no major marks, fully functional. Overall: excellent condition