Chasing 60 hz hum


I have an MC 7150 and an MC 7104 in my system, both plugged in to the same circuit on a power strip. The problem is that McIntosh went away from two prong and moved to 3 prong grounded wiring when the 7104 came along. I also moved from a C39 to an MX119 preamp, again the change from ungrounded to grounded. Having these units together on the same circuit produces a nice fat 60 Hz hum. To cure this, I used cheaters (3 to 2 adapters) on the 3 prong devices and this works.......mostly. Then, every few months the hum comes back and I go to the strip, wiggle one of the adapters a little bit and it stops....but this is a pretty goofy way to run an otherwise nice railroad....anyone got any ideas that are not radical (such as rewire the house!)
broimp
Greetings,
I lot of people will say not to use a cheater plug, but it works. A lot of dealers use cheater plugs also due to AC hum.
Having an AC hum happens in a lot of systems.
I would suggest using the cheater plugs and maybe going with a Very Good power strip or possibly a PS Audio Ultimate Outlet, I have seen them listed here. I have used them for years in my system except on power amps. I did use them for awhile on my amps when I went with the cheater plugs with no ill effects.
After talking to my dealer I now just use the cheater plugs right into the outlet.
I had the same type of problem with AC hum, I totally disconnected the ground wires that comes from my breaker box and installed a real Isolated ground to my outlets. I ran a dedicated ground from the outlets to a water pipe in my house. I'm on a well system at my house and my well goes down 250ft. Could not ask for a better ground. Cleaned it up a lot but not totally, so I'm also using cheater plugs.
Getting rid of the hum using the cheater plugs made my amps sound Great. After talking to my audio dealer he suggested to get rid of the Hospital grade outlets that I have and go with the MIT outlets. Should get them soon. His opinion was Hospital grade outlets are not meant for audio, and I should get a nice improvement with a audio grade outlet.
If budget allows maybe a PS Audio re-generator or some other brand of power conditioner. I have read some very positive reviews of the MIT Stabilizer and the Audience ARP2-T.
I'm also purchasing a MIT Stabilizer for my front end equipment.
Hope my opinion might help you.
Joe Nies
Does the 7150 have a two-prong cable? If it has a non- polarized plug, take a voltage reading from the chassis to the screw that holds the wall-outlet cover in place. Reverse the plug and take a reading again. The plug orientation with the lower voltage reading should be the quieter of the two.
2) The filter capacitors in these components power supplies are supposed to filter out 60 cycle hum after the line voltage has been rectified."Leaky" or worn out caps will not filter the ripple, leading to increased hum. In older equipment replacing the caps might be worth looking into.
Joenies....glad you got rid of the hum, but cheaters degrade the sound of your system....instead... remove the plug from the wall and make the necessary wire changes behind the wall.