I have an original era PH15 from the early 90s. it's 6x50. You can also combine the channels to get 5,4 or 3 channels. A good price these days is probably around $100...just make sure you have the adapter cord too. The design problem with this (and other ADS amps) is the plug that that converts RCA signal from source to an 8-pin plug that goes into the AMP. I am getting ready to mine back in for 4th system. Coupled with ADS speakers, they have a warm great sound. ADS is no longer, I think they got bought out by Rockford a long time ago.