Mozztronics EX-1 Expander Drive Pedal


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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 can’t “dial in” 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.

Mozztronics uses the industry standard Boss style 2.1mm center negative 9V DC socket for the power supply connection. (these do not run on 9v battery so a power supply is a must!)


Mozztronics produce a range of handmade Guitar and Bass effects pedals in Melbourne Australia.

Mozztronics makes a limited range of effects pedals. I see no point in making something that everyone else makes, or a clone of a famous pedal, i want to make something a little different. I also want to keep all my products as completely analogue, with absolutely no digital electronics, not even a charge pump switching power supply.

But you make a compressor, a tremolo, a solid state dirt box (expandrive) i hear you say. Well yes i do, and i try to make these different to what is on the market. My compressor uses a different approach to the Ross / Dynacomp clones that fill the market, and i also have a bright switch especially useful for guitar. My tremolo has sine & square LFO waves for modulation and while similar to others on the market, does the basic tremolo job quite well and it uses an old school opto device to get the tremolo effect, the same sort of opto device used on the classic opto compressors. My solid state dirt box (expandrive) offers treble boost and cut (instead of just a treble cut on many others) as well as adjustable asymmetry and expansion, so while similar to other products on the market, i hope to make my products different enough to offer useful advantages to the standard tube screamer & distortion + and their many clones.