At lower settings the tone gets so muffled that you won’t be able to detect any breakup.
The Voltage knob on the top adjust the voltage applied to the circuit.
It’s actually 10 different combinations of various clipping diodes plus diode-lift/clean boost, arranged so that the most clockwise position is the clean boost and from there on the diodes offer progressively earlier breakup in the Drive knob setting.
To me, it strikes me almost like a guitar’s tone knob — it affects a very broad range of upper-mid frequencies, or perhaps it’s dealing with overtone content.
Set to the highest position, the pedal sounds most open, saturated and articulate. The manual describes it as warm and smooth, and while it’s not untrue, to me in the lower half of this knob the tone sounds rather muffled or muted — like throwing a blanket over your ears.
It is misleading, though, since the manual says: “the V-Drive’s Select switch replicates the diode type and configuration of the most popular overdrive pedals from the ‘80s and ‘90s as well as some of today’s most sought-after boutique designs.” (The manual never specifies which pedals it’s emulating — but technical info re diodes is at the bottom of this post) That kind of language makes one expect sounds like Tube Screamer or Blues Breaker or Distortion or other popular overdrive designs, each sounding distinct and different.
The Tone knob also does what’s expected, dialing in the treble content of the pedal — but as the manual indicates, the frequency range it affects is high and turning it down really doesn’t take away note definitions very much — higher setting sounds more in-your-face and lower setting makes it sound farther away.However, the effect of this knob on most Select positions is almost non-existent.