I just picked up one of these used retail is over $300.00 I got mine for $150.00. It seems like a decent quality boom op headphone amp it is a bit heavy and runs on two 9v but since I use rechargeable Ipower 9v I could care less about that. I am doing a short film next week and production insisted that I have waist mounted headphone amp for there boom person. I tried to explain to production that I can just sent him a headphone feed but this is what they want so I just do what I am told. Overall It looks like a decent design and should serve its purpose well. It can also be a single channel preamp but since it has no meters it is fairly useless for that purpose.