This channel is a conventional Super Hard-On™ (SHO). Its gain control is on the far right, and it's LED is yellow. If you are familiar with the SHO, you'll know that it's a very sparkly sounding high input-impedance preamp with incredible headroom, wide-ranging gain (unity to 60 X), and a maximum volume that will knock out your fillings. Channel one has no Master Volume control, but it's cascaded into Channel 2, which does...

This channel has the very same circuit as Channel 1, but the bleeder resistor on the output has been replaced with a Master Volume control, which allows the user to turn down the output volume even if the gain is set quite high. The knob on the left is the gain, and the middle knob is the Master Volume, and the LED is red. When both channels are on, or if only Channel 2 is on, the Master Volume is active. If you leave the Master wide open, you have two identical SHO pedals in one box, which are cascaded.

You might wonder just how insane this pedal sounds when you crank up both channels and turn them both on. A Les Paul continues feeding back at any audible volume level on my Marshall when both channels are wide open, and that's with the amp set at 1. Of course, this is not the only setting on the pedal. There probably isn't a musician around who wouldn't be happy to have multiple clean boost pedals set to predictable levels available on stage. This pedal gives you a total of four volume levels, ranging, at your choice, anywhere from perfectly clean to ragingly overdriven. Level 1, your guitar is true-bypassed with both channels off. Level 2, you turn on Channel 1. Level 3, you turn off Channel 1 and turn on Channel 2. This is easy because you can put your foot on both switches at once and alternate between the two channels if you want. Level 4, you turn on both channels.

First off, with your amp on standby, plug in the guitar to the input jack (it has a guitar next to it), activating the battery, and the amp to the output jack (it has a speaker). Set the levels on both gain knobs (outside knobs) anywhere up to 3:00, and the Master anywhere you want. Step on the switches several times to equalize the voltages on the input capacitors and eliminate popping noises during switching. Turn your amp volume to a low level to start, and try listening to the two different channels individually and together, adjusting them slowly until you get to the levels you want. Set the Master Volume so that your final output level with both channels active is low enough not to blow up your amp. Remember that Channel 1 works best as the loud clean boost, and has no Master Volume when used alone. Channel 2 can actually distort by itself at any volume level using the Master to limit it's output level. When you turn the gain knobs, it's ok if you hear a rushing/crackling noise. That indicates that the gain and bias of the transistor are being reset. This noise gets more intense toward the right on each of those knobs, but does not in any way indicate anything is wrong with your unit. 

Zvex has taken a lot of flack for the SHO "crackle okay" knob's noise, which people mistakenly interpret in many different ways. There have been reviews where the user believes that the pot is "cheap" or that it's "old," or "bad." This is not the case. The SHO uses a revolutionary approach to controlling the gain that resets the headroom, gain, and bias of the transistor at the same time, effectively re-designing the circuit for the optimum settings at each volume level. When the knob is not being turned, the unit makes no crackling sounds. It's not a simple volume control. If it were, the SHO wouldn't be so special. The SUPER-DUPER 2-IN-1™ has this same kind of control for each channel.