Effect pedal from the 70's/80's. It's a 6-band EQ with battery operation only (you can't use a power supply with my model but the battery life is very long - about 1 year). It's always on because it has no on/off switch.
Very easy to use: Simply slide the frequency band faders until you get the right sound. I have the user's manual but I didn't need it.
I'm using it with my Rockman Sustainor or my MXR Distortion+ and the sound is perfect. You can shape the sound to get a big bottom end or a very sharp high end (wah-wah like). I believe it does provide "something" to the original sound. And I love it.
I've been using it for 5 years. At the time I payed almost the same you'd pay for a modern Boss EQ pedal. The possibilities are plentiful, you just have to experiment with all the settings you can imagine. Extreme settings can ruin your sound (but that's normal). You can only get it secondhand now and although it's very difficult to find one, it is worth it.