Hammer,Is that the Prescription Electronics pedal?
I recently made myself yet another Foxx Tone Machine clone, and decided to change the type of diodes used to produce the octave. The FTM is my favorite octave-up unit, chiefly because of how robust the octave is. But where one would normally need to be well above the 7th fret to hear octaves, this thing can now produce them below the 5th fret. Impressed the heck out of me.
Of course, very few, if any, of the analog octave-up pedals produce a "clean" octave, since the method used to produce the doubled frequency itself produces at least a little crossover distortion. It's also the case that many use a pair of clipping diodes to produce a simple compression that creates the illusion of the octave lasting longer. That also tends to yield a dirtier output, although there are ways to reduce that aspect.
Note as well that ALL analog octave-up units will produce a quasi ring-modulator tone if you do double bends. That's why the Dan Armstrong "Green Ringer" - a barebones octave-up unit - was called the Green Ringer.