There are many variants on two common designs. The tube screamer uses diode clipping around an op amp feedback loop. The distortion + has diode clipping to ground after the main gain stage. Often the distortion stage is followed by a low pass filter to smooth off the sharp clipping caused by the diodes. While these designs sound good, there are some features you canÕt Òdial inÓ with these types of pedals. Some people use different diodes with different forward voltage to get a different sound. So this is the Mozztronics take on this style of pedal. We use the diode clipping to ground arrangement, but we have added adjustable asymmetry, and an expansion control which will control how much the character of the distortion changes as you push the guitar harder. GAIN controls the amount of gain from the first stage, TONE controls the amount of treble in the output, from treble cut to treble boost, VOLUME adjusts the overall volume out of the pedal, EXPAND controls the amount of signal expansion (subtle but audible), and ASYM controls the asymmetry of the clipping. This is great for crunch rhythm tones, and gives nice drive sounds when driven hard. This is great in combination with the TD-1 tube driver for a really smooth lead sound. We suggest using the EX-1 before the TD-1 in the signal chain and set the EX-1 for crunch rhythm, and the TD-1 for lead, but there are no hard and fast rules. Experiment with the order of your effects to find what you like.