This is a very rare Harmonizer for sale. This is the second one I'm listing. As for the operational check, I've confirmed that it powers on without any issues. I was able to connect a PC sound source through this device to an amplifier and get sound from the speakers, but I couldn't tell at all if the sound was actually being altered by the Harmonizer. However, when I sold the first one, the customer said something like, "It's perfect!" and gave me a good rating, but I'm not sure of the truth. Since I'm also ignorant about this, please consider this a junk item when purchasing. Please understand that this is a junk item and no returns or refunds are accepted. Please read the comments and purchase accordingly. Also suitable for collections, etc.