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Buzzzzz - plasma and amp.

Do you have the cable tv coax cableplugged directly to the Samsung or is the Coax going to a cable box and from the box to the TV via HDMI. I have learned a lot of ground loop problems are because of the coax cable or sat not being properly grounded using the coax cable.

I have a Samsung plasma and never had an issue with buzzing.
 
Victory over the bees!!! Thanks guys - I unfortunately solved the problem. I state "unfortunately" because it turns out that, one way or another, it's the amp. After moving I found my old Sherbourn 5/1500A amp and decided to hook it up one speaker at a time to see if there was any noise coming through. One-by-one and at each stage no buzz (except from what is coming from the TV itself - Matt, I'm in Ohio so no problem with elevation but a good suggestion. I just think I have a noisy unit). I can live with the buzz from the TV but the noise coming through the speakers was driving me nuts.

So is it that simple? It's just the amp? Is it something worth sending back to Rotel or is it even a problem they could "fix"? It's the RMB-1095 model. Purchased from a store that no longer exists.
 
My feeling is that it's still a ground loop issue, but different components may be grounded differently and hence the buzz materializes differently. You said you're using XLR for the main amp; have you tried plain 'ole RCA instead, just to see if that has any effect?

How is your TV sound connected to the preamp, or is it? I'm guessing you've got HDMI going *to* the TV, but when you're watching live TV, how is the sound getting to the preamp, from the TV itself or a cable box, or...? Since this seems to happen only if the TV is on, it seems the TV is the ultimate source of the buzz, so I would not necessarily conclude that the amp is faulty.
 
Have you tried plugging all the power cords into the same surge suppressor? If not, maybe some are on one circuit breaker & the rest are on another...... just a thought.
 
Good questions. I am not yet ready to throw the Rotel over the side of the boat yet. The sound was present when the speaker wires were connected and there were no cables connecting the amp to the preamp.

In terms if other connections, HDMI running out preamp (monitor out) to TV, cable box connected via hdmi (sound and pic) hdmi from PS3 to pre, Xbox component to pre.

Yes, all power cables are plugged into the Belkin unit. And I actually borrowed the power cord from the Rotel when I switched in the Sherbourn.
 
Ok I'm confused. I thought the buzz only came when you turned on the TV? Or is it just that the hum gets louder?

Right, if there's a noticeable hum when nothing at all is connected to the amp (except speaker cables), then yes I might think the amp is at fault. Is it coming from all speakers connected to the amp?
 
Sorry to be confusing. Here's my best explanation: The buzz originates from the TV. The way that I can tell is that when everything is on but the TV, there is no buzz. Turn on the TV and the buzz is there both coming directly from the TV and through each speaker and will change in intensity depending on the screen brightness (a result of the fan in the TV is my guess). Leave the TV on, turn the Rotel amp off, and all you can hear is the fan noise from the TV itself - nothing coming through the speakers. Everything on, remove all interconnects (XLR) the sound is still coming through the speakers with speaker wires still hooked up to the Rotel amp. Start to take away speaker connections from the amp with everything on, the buzz through the speakers gets a little quieter but is still there in the speakers that are still connected. The speaker that is disconnected obviously is silent.

Switch in the other amp, connect everything and turn everything on, and the buzz coming through the speakers goes away- just the normal hiss is present. The buzz coming directly from the TV is still there but it is now just from the TV and not being transmitted through the speakers with the other amp connected (also using XLR cables).
 
Ok, so if I get you right, there's buzz that starts when you turn on the TV, even if NOTHING is connected to the amp but the speakers? That's pretty wild, but it seems then that there's some electromagnetic noise/interference generated by the TV that's somehow being picked up by the amp. Like one or both components is not properly shielded.

The only thing I could suggest then is to move the amp somewhere further away from the TV, see if it changes things. Or perhaps try going the I'm-crazy-and-aliens-are-probing-me route :laughing: and somehow put layers of aluminum foil between the TV and amp, but without blocking any heat vents. Otherwise, not sure what else you can do aside from changing the TV or amp.

And you've tried plugging the TV and amp into different plugs - either on the same or different home circuits?
 
They ARE out to get me. The buzz is how they communicate... :sci-fi-grayalien:

I have tried plugging the amp into a different location in the room but I think it's on the same circuit. New house so have to find another plug farther away. Unfortunately, if that helps it doesn't do me much good as this is a dedicated room so it would be hard to either move the amp further away or run a line out to another outlet. I can see if that does work if an electrician can get a dedicated line into the room.

So, yes if the amp is on, speakers wires are connected but no XLR/RCA cables plugged into the amp, and the TV is on, the buzz sound does come through the speakers.

Thanks for all the help! Very much appreciate taking me through this and helping me root out the problem. Going to try some other things - like plugging in the amp in the room by itself with a speaker wire connected to a small bookshelf speaker I have to see if it's still doing that. Then move it to another circuit to see if there is buzz.
 
If changing only the wall plug location (by temporary extension cord or whatever - and try that for both the TV and the amp, actually) makes any difference, there are surge suppressors that also include line noise isolation. This is what I have (tripp lite isobar):

:text-link:

It's possible that by separating the TV from other components, that interference would go away. But that assumes the noise is being transmitted through the power system, as opposed to EM interference from simple proximity. In theory it could be either, I suppose.
 
I am working at home so had some free time and I tried a little experiment (I don't work for Yahoo), just plugging in the Rotel amp with a small speaker attached by itself and plugged into another outlet (but at the same time having the TV on, other amp plugged in, basically everything running). I didn't hear anything through the one speaker and the Rotel. So I moved on to something else.
- I then connected my center speaker to the Rotel and added an RCA cable plugged into the preamp, all with the TV on. Quiet but something very faintly there - a hiss? So I thought, why not hook up the Rotel with all RCA cables to the preamp and all the speakers? So I did. Well, the bees were back though at a slightly different pitch (about the same volume). As I took speaker wire out, the sound got a little less, then remove another speaker, it got a little less, repeat.
- Does it make sense that this effect is cumulative? The more speakers that are added, the louder the buzz throughout? So, to explain further - when all 5 speakers are connected, normal loud buzz. Listen at the front left, remove one of the surrounds, and the sound gets a little less. Remove the center, the same.

Then I plugged back in the Sherbourn and the buzz was gone. Hard not to come to the conclusion that the Rotel is at fault from picking up the TV fan noise in some way. At least that's my conclusion after my very "scientific" process.
 
It's possible the speaker wires are acting as antennas and picking up the EM interference from the TV, and somehow feeding that back into the amp (via ground or something). But right, doesn't seem like there'd be any way to prevent that short of swapping out the amp... unfortunately.

Did you try plugging in the amp via extension cord from another room/circuit, but otherwise in its usual place (with everything connected)? Just curious if that'd make any difference, but I'd guess not from what you describe.
 
If the buzz is coming from all the speakers, then unplugging one will make the buzz sound quieter because one fewer speakers are making any sound.

it is possible this is EM noise as modern electronics use digital power supplies which often have a ton of high frequency noise from the rampant use of square waves in the power signal to get to the right output level in a small package.
 
You know my Samsung is plugged into an Isobar 10 and I never have heard any buzzing. Maybe gangsta Pauly is on to something.

Flint you lost me at "square waves". :text-imsorry:
 
To me, that is a bit over the top. Just get one of the basic beige models for $20 to $30 less. If beige is not acceptable, the lower end black model is fine.

What are all those features for, anyway? The unit filters AC noise on every two AC outlets and has good surge suppression. That's all you need.
 
Thanks, picked up the beige ISOBAR8.

On another note, going to send the Rotel amp to the shop to see if they can identify any issues with it.
 
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