I put this pedal between a vintage Rhodes electric piano and my current practice amp.  The tremolo effect is nice and can be adjusted to give the Rhodes a bit more "life" in its sound.  However, after what seemed like a short time, I noticed that I had a lot of amplifier hiss with the pedal turned off and the output volume had gotten really low.  The battery was almost used up by this point.  The good news is that after I connected a 9 V power supply to the pedal, the hiss went away and it was back to working really well with good output volume.  A power pack is pretty much mandatory with this pedal.  A 9 V battery has way too short a lifetime to be useful.  Apart from that, I'm really pleased with the sound for such an inexpensive pedal.