Hi, Just bought a used Gallien-Krueger RB400-III head and tried it out last night for the first time with some very discouraging results. I rented an Ampeg SVT-410HLF 4ohm cabinet for the evening to plug into and fill the room. During soundcheck I noticed that I had to crank the input and master volume on the GK full out to get enough volume (and it still didn't seem like enough). We went on about 30 minutes later and when I turned on the amp it was way, way louder. I was able to turn them down to about 9 o'clock and get a comfortable output. About 3 or 4 songs into the set it seemed to quit on me but I noticed that there was a little sound and then cranked it up again and it was back like at soundcheck. I played like that for about 2 songs and it kicked back in again and I had to turn it way down again. The soundman seemed to think that it was related to impedance but the GK is rated for 240 watts @ 4 ohms and about 180 @ 8 ohms so I thought that I would be good with the 4 ohm cabinet. Anyone experience anything like this before? Any idea if it would alleviate it by getting an 8 ohm cabinet, or is the amp fried? Thanks for the help.