The pedal featured the same controls as the Mu-tron III and incorporated a "Boost" feature, which activates an internal pre-amp and changes the function of the gain knob giving the Q-Tron a sound almost identical to the Mu-tron III. Another feature added to Q-Tron was an effects loop switch and attack response switch. Units with these features are called the Q-Tron+. A smaller more compact version, the Mini Q-Tron, is also available, as well as an even smaller version, the Micro Q-Tron. Electro-Harmonix also currently produces a modulated envelope filter, the Blurst  Electro-Harmonix currently manufactures over one hundred other pedals. These include the Graphic Fuzz (a fuzzbox which includes an EQ section), the Frequency Analyzer (which creates ring modulation) and the Voice Box, a vocoder. The Voice Box has been included in a series of demonstration videos produced by Jack Conte. Electro-Harmonix has also made a few small power amp pedals for use as a simple guitar amplifier. The EHX 22 Caliber was a 22 watt solid state pedal capable of driving either an 8 ohm or 16 ohm speaker cabinet. It has been discontinued. The 22 Caliber was replaced in the lineup by the EHX 44 Magnum, a similar pedal capable of driving the same speaker load, but at a 44 watt output. Several pedals produced in the decades prior have also been discontinued, many of which are still in high demand for their unique sound. These guitars were only available from EH for a very short time in 1974. They were available through a special offer for $87.50 with the purchase of $50 or more in certain scratch-n-dent EH products. The list price was $187.50. They didn't buy out a warehouse and put their name on them. These are the model names and descriptions: EH-7010 EH acoustic guitar (mahogany back and sides), EH-7020 EH acoustic guitar (D-28 copy, rosewood back and sides), and EH-7030 EH acoustic guitar (D-41 copy, rosewood back and sides, pearloid binding and inlay, 3 piece back). They bought them from Moridaira/ Morris Guitar who at the time were the best guitar maker in Japan, making guitars for Fender and many big companies. They put the EH on the guitars.