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Old 21st December 2006, 07:05 PM   #11
dfdye is offline dfdye  United States
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"Then why don't you run after it!!!!"

Oh wait. . . That's not the right response. . . .


(Sorry, I couldn't help myself when I saw the refrigerator comments. )
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Old 21st December 2006, 09:45 PM   #12
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I would want to test the wall outlet for a possiable mis-wired outlet.
Using a device like this:

http://tinyurl.com/yyduxn

just to be sure everything is A-OK. Also be sure to check the Fridge and other outlets too.

johnm
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Old 22nd December 2006, 03:04 AM   #13
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For what it's worth:

I built my first gainclone with amp and power supply in the same enclosure. I had the same problems you had and more. I tried everything that the very helpful forum members suggested.

Then, just for the heck of it, I rebuilt it in two separate enclosures. All the problems disappeared. I've built 3 more since, in separate enclosures, and have never had a problem with hum or EMI.

Again, for what it's worth.
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Old 22nd December 2006, 01:02 PM   #14
CarlosT is offline CarlosT  United States
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Quote:
Originally posted by burnedfingers
Get rid of the stove and refrigerator.


Sorry, couldn't help myself.
Along the lines of wacky (or not so wacky) solutions...here's AndrewT's favorite

Take off the mains AC ground and do not connect it to chassis...isolate it with a piece of electrical tape. Then go out and buy yourself a little GFCI plug-in device for safety like these little Leviton items.

http://www.twacomm.com/assets/pdf/19157.pdf

VOILA! No more hum...guaranteed. Do the test for yourself. Run the amp with along with the other noisy appliances in your swanky place and disconnect the mains AC ground for a second.
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Old 22nd December 2006, 01:06 PM   #15
CarlosT is offline CarlosT  United States
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Notice that most Adcom amps do not come with a 3-prong power plug. Why? Could it be because the AC ground noise is a bi**h to tame?
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Old 22nd December 2006, 01:18 PM   #16
poobah is offline poobah  United States
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The EMI filters mentioned thus far should help... I use them on EVERYTHING I build.

Also, consider putting a couple of TVS, Transient Voltage Suppressers, across the outputs of your PSU. These are really nothing big zener diodes. They will clamp transients that can ride through PSU when the app's switch.



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Old 22nd December 2006, 04:35 PM   #17
CarlosT is offline CarlosT  United States
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I think that in my design, I will isolate the RCA input grounds from the chassis and not join the amp's starground to the chassis/AC ground...that shoudl do it.
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Old 22nd December 2006, 05:47 PM   #18
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Quote:
I think that in my design, I will isolate the RCA input grounds from the chassis and not join the amp's starground to the chassis/AC ground...that shoudl do it.
Yeah! This is correct.
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Old 23rd December 2006, 02:18 PM   #19
CarlosT is offline CarlosT  United States
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An interesting side benefit to floating the signal and DC power grounds off the chassis is that all the concerns about using an LM3875T (nekkid LM3875) versus the plastic package LM3875TF and accidentally grounding the exposed chip tab on a chassis part (thereby ruining it if the chassis is grounded to the DC power ground) go out the window. N'cest pas?
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