2. tech-talk
  3. 1268377902

60 Hz Noise Reduction

How do I eliminate 60Hz hum from my audio system?

HISTORY:
I recently purchased an Acurus A200 to increase the volume level of the front channel of my second system. When I connected the unit I noticed a 60Hz hum coming from both front speakers. I'm thinking the new set up has created a ground loop, or the units with no AC ground plug (2 prong AC plug) have a floating ground. The 2 prong AC units are Denon AVR3805, and Velodyne ULD15. So I would like to get some ideas of things I can do to eliminate the 60Hz hum This set up is a hodge podge of equipment left overs from the past.

OLD SET-UP (No 60Hz Noise)
Denon AVR3805 driving front, center, and surround speakers.
Denon preamp out to ULD15 controller/amp driving ULD15 sub.

NEW SET-UP (60Hz Noise)
Denon AVR3805 reciever which powers center, and surround speakers which are Monitor Audio bookshelf speakers. Denon pre-amp out to ULD15 Series II controller/amp driving Velodyne ULD15 sub. ULD RCA output to Acurus A200 amp input driving Monitor Audio GS10 for front.

Ideas Appreciated
Aaron
aweaver555

Showing 4 responses by jea48

jea48
4,309 posts
 
Just guessing you have a CATV box connected to the system. Disconnect the coax cable from the CATV and check for ground loop hum. If hum is gone buy an isolation transformer for the CATV coax cable.
http://www.jensen-transformers.com/an/generic%20seminar.pdf

http://www.jensen-transformers.com/an/an004.pdf
jea48
4,309 posts
 
no cable box just TiVo.
Aweaver555
Where does the TiVo receive its signal from?

I think I nailed it by attaching earth ground to Denon Receivers chassis ground.
Aweaver555

Not a good idea. If the Denon has a two wire polarized plug that means the equipment was designed and manufactured with double insulated ac power wiring, therefore an equipment ground (third wire) is not used. An earth ground connected to the chassis could degrade the sonics of the unit. More than likely the signal ground of the unit is connected to the chassis. By earth grounding the chassis EMI/RFI AC noise could enter the electronics of the unit through the ground wire.

Jensen VRD-1FF

http://www.jensen-transformers.com/datashts/vrd1ff_manual.pdf
jea48
4,309 posts
 
I'm assuming that if I connect the chassis to AC ground instead of earth ground it would cause the same EMI/RFI noise problem. or worse correct?
03-15-10: Aweaver555
Equipment safety ground, ("U" shaped hole ground contact on the AC wall receptacle), is often referred to as earth ground. I assume that is where you connected the ground wire from the Denon chassis to earth ground.

TiVo/Cable Loop
The Cable TV, and TiVo coaxial are not connected to the Denon unit. 03-15-10: Aweaver555

How about the audio-out from the TiVo? I assume you have interconnects,ICs, that connect CATV audio to the H/T audio system. The ICs complete the ground loop circuit from the CATV coax grounded shield through the audio equipment and out the equipment grounding conductor of the Acurus A200 to the equipment grounding conductor of the AC wall receptacle.
Jim
jea48
4,309 posts
 
I reconnected the house cable with none of the devices connected, and then reconnected seperately to determine which device was the source. Unfortunately when any single device is connected the noise returns.
When you get the Jensen iso transformer install it between the main CATV coax and the "line in" of the splitter . That should solve your problem.

For a temporary fix you could use a ground cheater on the power plug of the Acurus A200.
Jim
.
More to discover