The Systech Harmonic Energizer was introduced in 1975 and was probably most famously used by Frank Zappa and are quite rare to come by. Original units are selling for as much as $1999! (which IMO, is WAY overpriced). It's basically a single band equalizer with a variable bandwidth, and they do sound quite good, albeit are a bit noisy. My version is an exact clone of one but with an added master volume control (the originals only had 3 knobs- Bandwith, Center Frequency and Gain. They came in a very large aluminum enclosure (see pic of the original below), but my verison comes in a 125B with all top jacks, and with a relayed true bypass.
