My true entry into HT started with a 950 and a 755 and some Onix rocket 750 speakers on 2/28/05. Well music being one of the 3 things in life that make me happy I upgraded in a big way in the last 5 years. But, the 755 and 4 rocket speakers are still there for surround duty. The 755 always had what I suspect power supply issues due to the fact that when the microwave or my girlfriends curling iron was on it would make the 755 amp hum. My mega dollar Krell amps are dead silent always. I do not see the need to upgrade the surround amp or speakers even know the rest of the system dwarfs them in comparison.

Now the problem is that the 755 is humming all of the time now. I have disconnected the input RCA's and it is still making a ground loop type hum which leads me to believe the power supply is going.

It figures it is a little over a month out of warranty.

I will give Outlaw a call and I suspect that they will help me because they have always been extremely helpful in the past.

Is there anything else I could try before calling them. I unplugged my PPP(power re-generator) and plugged the 755 strait into the wall to see if that was the issue but no luck.

Any suggestions will be greatly appreciated.

Thanks,

When you shut the 755 down it still hums for 5 to 6 seconds. I am assuming that is the capacitors draining. There are three Krell mono blocks and two ice sub amps also hooked up that are silent which also leads me to believe that the processor and the input power are not the issue.

The hum is getting to the point to where I would rather not have surrounds than have to hear a humming sound all the time. I have narrowed it down to line noise. The amp was always sensitive to extreme line noise but now it is very sensitive to the noise. I can turn on a light and the humming gets louder. The more lights I turn on the louder the humming gets. These are regular 100w bulbs not the curly fluorescent ones because those make the hum even worse. There are no dimmers on the line either. The line is at 122 volts so it is not starving the amp. I have a call into Outlaw and I hope we can get this solved.... I am wondering if it is common for an amp to get more sensitive to line noise as it ages?

Well I talked to service and they believe it is line noise also. The problem is that my other amps are silent and the noise has just recently become an all of the time issue with the 755. Outlaw thinks that my service is too small for my house and while I agree, nothing has changed in the house to warrant the sudden sensitivity the amp has to the noise. The amp is just over 5 years old and I would have to say it served me well but I am starting to believe it is time to put her down. That was the last Outlaw piece left in my system and I do not want to chance a hum issue again so I will bid all farewell and good luck. My parting words will be that I have always been extremely satisfied with Outlaw's products and service and they are an excellent value for the money. It has been a pleasure!!!

Putting the amp out to pasture due to a ground loop hum seems extreme. Have you tried powering it from another recptacle on a different breaker circuit? Is it grounded the same as the rest of the components?

Ok, I ran a 12gauge extension from the dedicated line for my main amps and now the 755 is quiet again. I did not want to spend money on a new amp for my surrounds so this is a solution for the time being. I am glad I do not have to use the 755 for a boat anchor. I is definitely a lot more sensitive to line noise than the rest of my system but when it is quiet it does its job nicely. I need to watch a movie to see if the circuit can handle the extra load.....fingers crossed.

For what it's worth, my 755 has always been a bit sensitive to line noise as well. When I lived in an older home with fairly ancient wiring, the only thing that worked was to put the entire system on a very fat UPS (APC Matrix 5000) that I had "laying around" when I decommissioned it from the office datacenter.

I live in a much newer building now with more current wiring and the 755 is quiet without the UPS.

Best,