Help With 60Hz Hum PLEASE
OK.....so I never made it all of the way to the testing sequence as stated above. I started to set up for the test, but when I get the 100lb. amp out of the equipment rack and set it on the floor. I decided to try a couple of things before I removed the rest of my equipment. In order to shorten this a bit I will cut to what I did the gave me a reason to pause and reflect. For this the amp is plugged into a dedicated outlet with NOTHING else attached. I ended up plugging in my iPhone directly into the amp using 1/8" to RCA adapter. Voila, no noise at ALL!. So with the iPhone plugged in with RCA connectors there is no 60hz hmm. So I decided to go ahead and plug in the xlr cable into the same channel that the RCA cable is plugged into. NOTE: the XLR cables were not connected to anything for this test, they were plugged into the amp only. The noise was back, although much softer. So then I flipped the "Balanced/Unbalanced" switch to "Balanced" and the noise was back. Unplugged the xor cable and the noise is gone. Bottom line. Every time I plug in the xlr cables the noise comes back. Even if they are not connected to anything on the other end. I am now, more than ever, thinking the problem is within the amp. Any thoughts? Any suggestions? |
jo3533, You cannot connect the XRL cables to the amp without the other ends of the cables connected to a load/source. If they are not connected to a load, like a preamp, and are just laying there open ended you basically have 5 antennas picking up RFI and sending the noise to the inputs of 5 power amps. If you have the amp on the floor that’s is definitely the hard part of the job. The Marantz 8801 is considerably lighter. But, before you pull the Marantz out of the rack do you by chance have an old DVD player? Or you could use your Sony multidisc player. For a test connect a pair of RCA interconnects from the audio out of the player to the front right and left channels RCA jacks on the Adcom amp. With the Adcom amp turned OFF, Plug in the power cord of the player and turn it on. You will not be playing any music through the player. DO NOT press start to play.(If you are using an old DVD player don’t put a disc in it.) By chance if a disc is in the player and you were to press play the music would be loud but not ear deafening. I still would not try it! Next flip the toggle switches on the back of the Adcom for the front right and left channel amps to single ended. Turn on the amp. Just a guess you will not hear the dreaded hum. Unlike when you were using the iPhone for a test which is battery powered, the player is 120V AC powered. The player is the termination for the single ended RCA interconnect cables. Both pieces of equipment are powered from your house’s 120V mains power.
Post back your findings. |
Ok, so I hooked up an old Koss CD player to my amp. fired up the CD player and then the amp. One note about this unit is that it only has a two prong plug much like my Marantz. The noise was GREATLY reduced. I could still hear it, but is was very faint. Just out of curiosity. Would better xlr cables help clean up some of this noise? I am using an inexpensive cable set currently. |
jo3533, Sounds good. You could still hear the faint noise, jmho, because the Adcom is rated at 300 watts per channel. Jmho, that’s probably the best an RCA singled ended ICs, interconnects, will do. You need to go with balanced ICs. Hopefully Al, (almarg) is still following this thread when someone posts on it and will hopefully chime in. Al can tell you the whys you will need balanced cables over single ended for the lowest noise floor possible. I take it you have not bought any new 1 meter or longer XRL balanced cables yet? For a test just pick up 1 pair for now. Try them between the Marantz and the Adcom amp. Connect them to the front left and right channel outs on the Marantz to the front left and right channel inputs on the Adcom amp. Don’t forget you have to / need to separate the two from one another. I would try to get the Marantz at least 18" to 24" away from the Adcom amp. Quote: |
