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  #61  
Old 12-29-2009, 02:07 PM
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Bobby D. Bobby D. is offline
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Quote:
Originally Posted by gfinlayson View Post
Bill,

If your amps and preamps require earth connections, then effectively by using 3 to 2 pin plugs you are removing the earth connection to the equipment chassis. This earth is provided as an electrical safety feature, and is mandatory.

The fact that it's plugged into an earthed line conditioner makes no difference, as the equipment chassis is still not earthed.

If you can give me a run down of all of the equipment that is connected together, I'll see if I can come up with any suggestions.

Graeme

P.S. I've had a persistent earth loop problem myself for some time which I've finally solved. My main hi-fi speakers and associated pre and power amps are used as the front channels on my A/V system.

If I disconnected the analog connection from the TV, the ground loop hum was still present. If I disconnected the SP/DIF from the DVD player as well, the hum stopped. It turns out my cable TV box audio ground shares the same ground as the incoming coax cable (which is earthed by the cable company for safety reasons). Even having no direct audio from the cable box still caused hum, beacause the SCART leads on the DVD and cable decoder have a common ground which is shared by the DVD's SP/DIF and this was ground looping via the Dolby digital processor to the amps. The solution was to switch the DVD to TOSLINK, and I was going to put audio transformers in the analog outputs from the cable box, but our cable provider is now doing new TV Drive boxes which have TOSLINK digital output. Now all of my music stuff is connected by RCA phonos, and all of the video sound stuff is connected via optical digital. No more hum!!!

I had the same problem with a ground loop between my house ground and the cable ground. I put a 3 to 2 prong adapter on my home-make amplifier and the hum was gone. The cable box is now the sole ground in the system (through the coax cable). The rule of thumb here is to allow no more than one external ground. I have never seen any commercial HiFi components using the ground prong in the power plug. Components are usually designed to "float" with respect to the mains.

If the hum persist but goes away when you unhook the cable line, there's a trick to isolate the cable box from the cable ground. Take two balun transformers (the adapter people used to use to hook cable up to old TVs that took twinlead) and connect the twin lead outputs of one to the other. Now you have a 1:1 RF transformer that breaks the ground loop. I would only try this as a last resort. Now that cable is a two-way digital system, the baluns might mess up your cable reception.

Bobby D.

Last edited by Bobby D.; 12-29-2009 at 06:15 PM. Reason: Clarification
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  #62  
Old 01-14-2010, 02:32 PM
stevet66 stevet66 is offline
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I solved my ground loop problem the saqme way, I went and bought the Hum X by Ebtech and now the hum/buzz is completely gone! This is also the safe way of doing it cause everything is still grounded. It cost me $70. Not bad.....
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  #63  
Old 08-02-2010, 02:48 PM
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Copa1934 Copa1934 is offline
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I too have the hum, and it is not good. :-)

I've been following these posts and tried reversing the plug (not polarized) and still have hum at no volume. Nothing is connected to the receiver other than rabbit ears. I had another receiver in it's place, plugged into the same A.C. and no hum.

Seems to be narrowed down to the receiver, but what in the receiver can be corrected to eliminate this?
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  #64  
Old 08-03-2010, 11:05 AM
FOXHUNTER NJ FOXHUNTER NJ is offline
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  #65  
Old 08-03-2010, 02:32 PM
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Copa1934 Copa1934 is offline
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Very cool and very helpful. However, my situation is a little different in that I have a standalone system, ie nothing connected but the speakers. I've turned off flourescent lamps and other "things" on the same circuit and still hear a hum, very low and faint. I suspect it's the system, unless of course due to the wiring (which is 60+ years old) may be shared on another outlet, where some other device is the culprit?
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  #66  
Old 08-05-2010, 09:24 PM
FOXHUNTER NJ FOXHUNTER NJ is offline
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  #67  
Old 08-07-2010, 07:11 AM
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raindance raindance is offline
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Quote:
Originally Posted by Copa1934 View Post
Very cool and very helpful. However, my situation is a little different in that I have a standalone system, ie nothing connected but the speakers. I've turned off flourescent lamps and other "things" on the same circuit and still hear a hum, very low and faint. I suspect it's the system, unless of course due to the wiring (which is 60+ years old) may be shared on another outlet, where some other device is the culprit?
No-one is listening to your question. Explain to me what receiver you are referring to that has the issue. If it is a tube receiver, some slight 60Hz hum in the speakers may be normal. If there is excess hum, usually it indicates that one tube in a push pull pair is biased way different to the other, or your smoothing caps are toast.

If you have a solid state receiver, your smoothing caps are probably toast.

I assume you are testing with the volume all the way down? Not set to the phono input?
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  #68  
Old 08-14-2010, 04:32 PM
FOXHUNTER NJ FOXHUNTER NJ is offline
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  #69  
Old 08-16-2010, 09:27 AM
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Copa1934 Copa1934 is offline
My ears are bleeding
 
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You say bad caps and hum go hand in hand, why not just state that from the start rather than make all the unrelated and unnecessary commentary prior to that?

If bad caps, then where do I start? What are the most likely points to check? Is it as simple as looking for deformed caps and then moving from there? If bad caps are located, and equivalent replacements are not available, is there a tolerance that is acceptable, i.e. can a cap with a slightly different value be used with little impact on performance? If not than the receiver may be a lost cause.

I don't know how it will help but the unit is a Realist STA-860 http://www.radioshackcatalogs.com/catalogs/1984/ page 10

As a side note, some people would say chuck the sucker, it's not worth it. If it can't be fixed, OK, but I try to live by the three R's and would just assume not add more HiFi to the local landfill if it can be avoided. Our love of vintage products does more than just keep the spirit alive, it keeps loads of cool stuff out of our landfills.

Thank you!
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  #70  
Old 08-21-2010, 10:55 PM
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michaelhigh michaelhigh is offline
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I have an Ampeg bass amp that has no polarity switch. If I hook up a bass pre amp (which I do for added tone and EQ) and wireless I can get some hummage from the amp. I have an Ebtech Hum Eliminator which breaks ground loops and quiets everything down well. You may look into a device such as that. You simply start with the offending member, plug the AC into the Hum Eliminator, then out to the wall as usual. Works miraculously to get the noise floor down dramatically...
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  #71  
Old 08-22-2010, 10:21 AM
FOXHUNTER NJ FOXHUNTER NJ is offline
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  #72  
Old 08-23-2010, 03:59 PM
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Copa1934 Copa1934 is offline
My ears are bleeding
 
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The way in which you approach the answer, in the second paragraph (installment if you will) was more what I was looking for. The prior post, to me anyway, came across condescending. This latter part is very professional and far more informative.

Now I have something to work with. My main issue now is whatever pots I can't visually identify as potentially bad, I'll have to rely on other sources (people) to assist or simply perform the work. Can't justify the cost of equipment to do it, unless it's something I can buy cheap (working) on eBay?

I'll check for deformed/bleeding caps and then go from there. I'm going to put in a separate post looking for a knowledgeable/trustworthy repair place in the area (likely will not be local, too small a community). Maybe find a good hobbyist?

Thank you very much for that more enlightening response!!!
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RS-1080, SX-680, 9090DB, STA-2500, STA-860, RX-V795

RS 40-4024a, 5b, 7b, Min-7, LX-5II, JBL L3, L88, HPM-40 (2nd Gen), Infinity 4000, Allison CD7, Advent1, V.A. Haydn (first Gen)

Sony DVP NS755V, Technics SL-1700, Sony WEGA DLP 60"
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  #73  
Old 11-15-2010, 05:29 AM
amapimp amapimp is offline
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Is the cdr player stacked on top or underneath of the amplifier????
Ian
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  #74  
Old 10-12-2011, 11:55 PM
Brent87st Brent87st is offline
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It is hooked to the "aux" jack, not a phono jack??
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  #75  
Old 10-19-2011, 03:35 PM
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1newbe 1newbe is offline
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Interesting thread guys, very informative. Thanks.
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