2. amps-preamps
  3. 1320771172

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

Showing 3 responses by jea48

jea48
4,313 posts
 
Al,

Here is an interesting post that ran over on AA.
Note the responses of the equipment manufactures.

Plain and simple good sounding equipment can be built without the need of an equipment ground if the manufacture would only spend a few extra bucks and use double insulated wire for his AC power.

Floating ground... Does it cause damage?
.
Jim
jea48
4,313 posts
 
I've never been able to figure out how to navigate through long threads at AA in an efficient non-confusing manner :-),
11-09-11: Almarg

LOL..... That's why it's called the Asylum....

Try this, it might be a little easier....

http://www.audioasylum.com/cgi/t.mpl?f=amp&m=156311
.
jea48
4,313 posts
 
11-10-11: Kirkus
Actually I've experienced at least as many grounding-related problems with "double-insulated" equipment as those with safety grounds. This is because they still have leakage reactances in their power transformers, and thus AC-related currents will still flow between their chassis -- this will now be flowing wholly through the interconnect shields. And for unbalanced interconnects, the shield resistance then becomes the primary dictator of the attainable hum level.
Al,

And in how many cases can the problem be blamed on the manufacture of equipment for not checking for the proper AC orientation of the primary winding of the transformer..... .
Jim
More to discover