What's new

Why do amps hum and receivers dont? (1 Viewer)

Ken Custodio

Second Unit
Joined
Dec 5, 2001
Messages
316
I recently added a Parasound amp to my HT and as soon as I hooked it up I got a ground loop hum from my digital cable tv. My cable company is coming out sunday, hopefully they will be able to fix it. Anyway, I just wanted to know why are amps so sensitive to ground loop problems and receivers aren't? I've had three different types of receivers and have never had a problem with ground loop hum. Just curious.
 

Saurav

Senior HTF Member
Joined
Feb 15, 2001
Messages
2,174
Did all your receivers have 2-prong plugs, and your amp have a 3-prong plug?
 

Arthur S

Senior HTF Member
Joined
Jul 2, 1999
Messages
2,571
Good question. So many people buy a separate amp to bolster their reciever. Often they are quite disappointed that the first thing they notice is hum and other noise with the separate amp.
I've never had a receiver that had either mechanical transformer buzz or electrical noise that could be heard from the listening position with no signal present.
Not true of amps. The transformers in many amps are large. The larger the transformer the more likely it will buzz. This has to do with the laminations and how tightly and carefully the whole transformer package is designed, manufactured and installed.
But the 3 prong plug issue is a major source of this discrepancy between amps and receivers.
Never the less, you hear far more about hum, buzz, and hiss from separate amps than you do about high power receivers.
What ever you do, don't use a cheater plug ;) .
 

Aslam Imran

Second Unit
Joined
Mar 1, 2002
Messages
286
Because most amps consume higher power than receivers (even when the ratings are similar), have bigger power supplies with torroids that are notoriously buzzy. Just take a wrench and tighten it down and you should hear no buzzing. Thats the nature of the beast.
 

Chu Gai

Senior HTF Member
Joined
Jun 29, 2001
Messages
7,270
Personally, I wouldn't go about opening up your Parasound and start tightening things as that would probably void your warranty (and besides, I think you're talking about something else). Rather than go through a litany of possible things for you to check, while waiting for your cable person to roll in, do a Google search on the terms Ground Loop Problem. Pick a few likely sites and run through the possible solutions. If possible, please post back as to what you found.
 

Mark Austin

Supporting Actor
Joined
Dec 28, 1999
Messages
639
Separate amps tend to be more sensitive to noise. After having the cable company change the ground to no avail, I went to a local B&M A/V store that did installations, and they had a cable ground breaker for like $5. Works like a charm. Another place to check would be sat installers who would also have them.
 

Ken Custodio

Second Unit
Joined
Dec 5, 2001
Messages
316
Separate amps tend to be more sensitive to noise. After having the cable company change the ground to no avail, I went to a local B&M A/V store that did installations, and they had a cable ground breaker for like $5. Works like a charm. Another place to check would be sat installers who would also have them
Mark,

Does that cable ground breaker work with digital cable? I have one built into my surge suppressor but it cuts out about half of the digital cable channels.

Ken
 

Nathan Cook

Agent
Joined
Apr 10, 2002
Messages
41
i hooked up an amp with some cheap unshielded cables that were run along the mass of all my other cables and such and i about blew my ears out with electrical noise when i turned the amp on.
 

Aslam Imran

Second Unit
Joined
Mar 1, 2002
Messages
286
I was assuming only the humming of the amp from reading the orignal post. This is differentiated from speaker hiss due to the amp which is a result of ground loop problems. If the speakers are hissing then go about it in ways described above but of there is humming coming from the amp interior, none of the above is going to help and the only solution is to tighten the torroid.
 

Todd Hochard

Senior HTF Member
Joined
Jan 24, 1999
Messages
2,312
Is there adequate voltage supply at the outlet the amp is plugged into? If the voltage is sagging when the amp is powered up, that will tend to increase the hum. It should stay above 110VAC at all times.
 

Robert Elliott

Stunt Coordinator
Joined
Feb 18, 2002
Messages
103
I have a completely different answer based on a reading of Bob Carver's patents on the Sunfire Subwoofer.

Your receiver doesn't hum because there is no ground loop issue with its internal amps. When you connect the receiver or pre/pro to an external amp via interconnects you have created a ground loop. The voltage/ground of the separate items is/can be different (based on your household ground loop I suspect) and when connected to each other via the interconnects, you introduce the 60hz hum.

Another major problem encountered by subwoofer designers is directly related to the fact that subwoofers are exceptionally prone to hum problems induced by power line "ground loops". Ground loops are caused by a redundant ground that runs from the wall plug or other suitable A.C. source where the subwoofer is plugged in, through the power line to where the audio signal source--e.g., a CD player, an FM tuner, a turntable, etc.--is plugged into the power line, and then back to the subwoofer audio input through the audio cable shields. This constitutes a loop called a "ground loop", and it generates a very undesirable 60 Hz hum. - From Bob Carver's subwoofer patent

You get the same condition frequently when connecting a receiver to an external powered subwoofer. Carver implemented a patented design in his subwoofer which eliminates this issue. How? In short by detecting the ground loop problem, routing the hum along two different paths using opposite phases so the hum cancels itself out.

That is my laymans understanding as I am not an electronics wizard but Bob spells it out in detail in his patent for those interested.
 

Arthur S

Senior HTF Member
Joined
Jul 2, 1999
Messages
2,571
Jeff

"What ever you do, don't use a cheater plug."

Take a closer look at the smilie.

Artie
 

Tim Hoover

Screenwriter
Joined
May 27, 2001
Messages
1,422
Pardon my ignorance (or perhaps I'm just missing the joke!) but why would you not want to use a cheater plug w/ a power amp?

Paranoia runs in my family...
 

Users who are viewing this thread

Forum Sponsors

Forum statistics

Threads
348,457
Messages
4,846,171
Members
142,321
Latest member
TurtlePen
Recent bookmarks
0
Top