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-   -   My amplifier makes a buzzing noise (http://www.diyaudio.com/forums/solid-state/6898-my-amplifier-makes-buzzing-noise.html)

Jimmy154 19th October 2002 12:41 AM

My amplifier makes a buzzing noise
 
My amplifier makes a buzzing noise in the left channel and right channal I think. This only happens when both my cable tv RCA cables and my computer RCA cables are plugged in at the same time. I had this problem with an older amp and the same equipment and it went away misteriously when I kept switching the RCAs from "TV/AUX" to "VCR1" to "VCR2" to "TAPE1" to "TAPE2" in many different combinations.

It might have not been a mistery, but I forgot what I did and nothing seems to be working now.

Does many body know what's causing this noise and/or how to get rid of it?

GRollins 19th October 2002 02:12 AM

It's only necessary to post a thread in one forum. Posting it twice just takes up space and annoys people.

There's a differnce between a 'buzz' and a 'hum.' For the moment, I'm assuming that you mean a hum. It's very likely that you've got a problem with ground loops in your system.
A ground loop is when you hook two separate pieces of equipment together and, due to differences in the power supplies or whatever, small currents flow through the ground from one piece to the other. Ground connections normally don't carry much in the way of current. When they do, it tends to make a racket.
As for what to do...well, your options are limited. The usual approach is to put one of those grounding adaptors on the AC line cord of the offending piece. This 'floats' ground for that chassis and keeps the current from flowing. However, some things don't like running with no ground and others are simply too dangerous to run without a ground. If you choose to go that route, you've got another option in that you can flip the plug upside down, which can also change things around, depending on how your equipment is wired on the inside.
Ground loops are persistent nuisances. You think you've tried every possible permutation of grounding, not grounding, and reversing the AC, and it's still there. Then you wander off in disgust...stop...wait a minute...did I try <i>that</i> combination? Go back and hit it again and get it.
Persistence is the key.
One other possibility that comes to mind is the idea that you're trying to hook in a computer. Computers use switching power supplies. If, perchance, your computer power supply is spewing RF junk into the signal path, you're pretty much doomed.
(What on Earth do you want to hook a PC into your stereo for, anyway? Ugh. Keep 'em separate.)

Grey

AudioFreak 19th October 2002 03:48 AM

I've removed the thread in Everything Else.

Regards,
AudioFreak
diyAudio Moderator.

BeanZ 19th October 2002 04:12 AM

Make sure that the common of your secondaries are firmly attached to the chassis and earth as a starting point.

BeanZ

Jimmy154 19th October 2002 04:48 PM

Sorry I didn't know there was an amplifier forum when I posted my question in "everything else."

Yes, it is a hum. There's also a slight high pitched buzz on the left channel which is bearly audiable and I don't care about.

I hooked my compter up to my stereo so I could play mp3's on my stereo without making cds.

I don't think it's the computer supply "RF junk" (whatever that is) cause I had this problem before with a different amp and different speakers, but with the almost the same kind of computer and definately the same power supply.

If you think hooking a computer up to a stereo is bad, then what do you consider hooking a computer up to a stereo using telephone wire to be? And it wasn't even good telephone wire. I don't think this contributes to the noise because I had this proplem before I extented my RCA's with 15 meters of telephone wire. But now that I think about it some more, it might be the telephone wire. I can't remember whether I had to remove the Cable TV RCA's from the back to stop the humming.

I don't know if it makes a difference, but this humming doesn't happen when the CD player and the Cable TV are plugged in or when the CD player and my computer are plugged in. It only occurs when both my Cable TV box and my computer are plugged in together.

I wish I could remember what I did to fix it before. I think I might have run the RCA's instead of from my Cable TV box to the amp, from my TV to my amp, but this isn't an option since I don't have RCA outputs on the back of my TV.

I thought RCA's used DC (And each RCA, left/right, has a pos and neg)? Are you referring to the power suppys of my cable TV box and my Computer? What are secondaries? My terminology is not up to par with either of yours I think.

I've heard of ground loops however from installing my car amps and I'm almost positive I know how they operate. I think I might go puchase a better RCAs between my computer and stereo, but I don't think this will solve the humming, for the reason I stated above (explaning how I tried it without the telephone cord). Also most MP3's (128 or lower) don't sound that great anyway, so better wire wouldn't help sound quality even if they do get rid of the humming.

CryingDragon 23rd October 2002 08:00 PM

ok
#1 for cripes sake don't use telephone wire for audio,it's very thin and has tons of resistance (in the k-ohm per foot)
#2 go buy some good RCA's bad or dirty RCA's will cause hell in low level long runs.
#3 disconnect your computer from your TV right now (audio or not it dosen't matter) because if you turn your TV on the magnetic feilds it produces will induce some noise in the line (normally you wound't hear it in the TV) and it can throw a spike at your computer and if it does you can say bye bye computer.
#4 i'm almost positive you have a ground loop between your components,try hooking Just the computer up the the stereo and try this (just to see if it works) plug you radio in the same outlet as the computer,hook it up with some new good quality wire and see if it sounds good,Post back about what happens and one last tip be Extremely careful about computer outputs you can't momentairily short a computer sound output like you could a TV cause you'll fry the sound card.
Also plug the computer into the TV/AUX port.

Jimmy154 25th October 2002 01:03 AM

The telephone wire produced the loudest humming noise. I got rid of it (the wire not the noise). I purchased 2 - 20 ft single wire cable pieces that go from my computer near the wall all the way to my amplifier across the room. Then the single cable from my computer splits into a 6 foot y cable (RCA's). I noticed that the long run was a problem like you said. Each time I added another 20 foot extension the noise got worse.

My computer and TV are not connected. My computer goes from sound card output to RCA's on the back of my stereo amplifier. My cable TV box RCA outputs go to RCA's on my amp. My TV and amp are not connected by RCA's and cannot be because my TV has no RCA outputs.

I tried plugging my computer into the same out let as my amp. My computer and monitor go into one extension cord with 3 plugs and into an outlet and then I moved it into a power strip with my amp across the room. And the noise did get a lot fainter. I think that's how I got rid of the problem before. My stereo and computer were plugged into different power strips and then I plugged them into the same one and my problem of the humming noise when my cable tv and computer are plugged in together went away. Except at that time my computer wasn't across the room.

I'm going to play with the plugs some more and see if I can get rid of the problem. And if I can't it's not that big a deal. I have VRC2 RCA's on the front of my amp and everytime I want to switch between my computer and the tv I just unplug one set and plug the other set in.

Why would you plug the computer into the TV/AUX rca's? Where would the cable box rca's go? VCR?

PS -- how do you build an amp? Just kidding:D

CryingDragon 25th October 2002 04:27 AM

Where do u have the Computer input now? i would not reccomend tape 1 or 2 since these may go through filtering stages witch are designed for cassete noise and not MP3 sound.
Now there is a minimal amount of noise that the computer will ouput that may be amped up by your amplifier. I realize that you want your TV in the amp too for movies and such but you may have to put the TV in another input to have both the computer and the tv hooked up at once. Since your cable box in providing the sound you may be able to use a 'y' connector to take the RCA's from your computers sound card and the RCA's from your cable box and turn them into one for the TV/aux input but i would not reccomend this and if i were to do this i would make sure either peice of equipment was turned off when the other was on to avoid added noise. Try putting the computer in the TV/AUX jack and putting the cable box in the VCR1 jack and see how it sounds.


And PS that would make for a MUCH longer reply post ;)


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