The VARIDRIVE is a genuine 12AX7 vacuum tube-based overdrive pedal. The circuit is Class A and the tube component is fully utilized to create the overdrive / distortion effect without other circuitry addendums in either hybrid or solid state form; i.e. pure tube only. “AUDIOPHILE quality”. As reviewed in “Guitar Player”, SIB! tube pedals remain a full cut above other pedals in this category due to their advanced, very clean circuitry. You can rely on SIB! products to tube-up any musical instrument application performance or studio session. Reference clean with instant, remarkable effects. The VARIDRIVES DRIVE knob (gain boost) delivers a wide range of gain from toothy / edgy overdrive to buttery smooth break-up distortion with just the right amount of compression and run-on sustain at all times. The handy GAIN toggle switch allows half-loading and full-loading ranges to assist you in dialing-in familiar dosages of the best 12AX7 overdrive out there. VOLUME + EQ SECTION = VOLUME, BASS, MIDDLE, TREBLE The passive 3 band tone controls are tuned to make any guitar / amp set-up sound its best. There is no pre-EQ’ing going on here. Pre-EQ effects circuits tend to make guitar / amp set-ups sound bland and too similar to each other. In addition, there is no masking. The VARIDRIVE faithfully preserves the original sonic flavor and tonal characteristics, harmonics, etc. of your guitar and amplifier.