Well I'll be....A 53 cent plug eliminates buzz on RMB 1095

[Britchie]

Well,

After many painstaking, time consuming, trial and error processes, I have eliminated the buzz from my tweeters (all 5 spkrs). Thanks to Geoff, I elimated the Ground on the RMB-1095 with an adapter plug that cost me 53 cents. My question is this....Is it safe to run this Amp without a ground? Should I have Rotel fix something and if so, what can they fix?

Brad

[ekkoville]

I used the same fix from the local shack.....amp runs fine for me with no additional heat appearant. Played several movies at loud levels and seems fine.

Erik :T

[brucek]

Brad,

The cheater plug you used effectively eliminates the third prong on the AC plug.
The "third prong" is the electrical safety ground and is there to protect you and anyone who uses your equipment from electrocution. This safety ground is a cold conductor designed to provide a path to ground for safety protection against internal shorts inside your equipment when equipped with the three prong plug.

The third prong connects back to your service panel (where it is bonded to the neutral wire), and from there is connected either or both to your house plumbing or external ground rod.

On equipment with a third prong, the metal case and external metal parts are all connected to this safety ground when you plug the electrical cord into the wall. If a component fails inside a piece of equipment and the 120 volts shorts to the equipments case, then that case is now live and can electrocute you. If the safety ground was attached, then a breaker would trip to indicate you had a fault. :E

On equipment with two prong plugs, they are internally insulated from the external case to provide this protection without the third wire.

Usually bringing another ground from a cable system etc, can cause some hum or buzz in A/V equipment, but this can be corrected with a little work. Ground loops caused by cable or dss TV are the easiest to get rid of.

There are those that rely on the ground connection provided by their interconnects and will use cheaters on all their equipment except for one. This one grounded device provides the safety return and then as long as the equipment that is connected to it has an interconnect cable, it is esscentially protected. This theory falls apart as soon as some unsuspecting person unplugs all the interconnects. I wouldn't advice using this method.

If you have a hum or buzz from an amplifier caused by a ground loop, then removing the safety ground connection to the amplifier (and perhaps other devices as well), can clear the resultant effect of the ground loop, but creates the safety issue. It's more advisable to try and clear the condition causing the ground loop than to mask its effect by applying unsafe practices.

In that regard, ground loops are sometimes a difficult task to track down and remove because there are a million reasons for them to exist. The loop is caused by a difference in the ground potentials in your system. Breaking the safety ground almost as often clears the problem, and that is why it goes away with the use of two prong power cords or with the use of cheater plugs. This easy fix is obviously tempting, since it's so easy. I hesitate to say that sometimes it's the only thing in the end that works on some troublesome equipment, ensuring that cheated piece of equipment is hidden away from anyone touching it. :roll:

Generally a ground loop can be tracked down to its source. Removing the problem can sometimes be a little more difficult.
You have to first ensure you have a ground loop situation by completely removing the offending amp and while using its proper three prong power cord, disconnect everything but its speakers and see if it still hums. If it does - you don't have a ground loop - fix the amp.

One of the other major culprits in creating ground loops is the use of more than one circuit in an HT system. The larger systems demand more power, so several dedicated circuits are sometimes needed. But even using a single circuit with different receptacles can cause a ground loop.
Residential houses use 240 volt "single phase" three wire power. The two "hot" legs are 120 volts and are 180 degrees out of phase. The loads in your house are balanced between these two legs at the service panel. It is advisable, if you do have two circuits powering your HT system, to ensure you are using a common leg. It is fairly easy to establish this.

Let me explain a bit about ground loops.......Even though the safety ground is a cold conductor, it can, and usually does, develop a small potential, through mutual inductance, wire resistance and various other reasons that can be different at each receptacle in your house.

When I plug a power amp into one receptacle and a preamp into another receptacle, the metal cases of these two units can have a small potential difference in their safety grounds which means that this equipment's metal cases are at a slightly different potential. When I connect a single ended (RCA) cable between these two devices, a small AC current can flow in the shield because of the potential difference. This signal is in the signal loop circuit and can cause a hum. An interconnect circuit has a loop path (completed circuit) that flows through the centre conductor of the interconnect cable and back on the shield. If there is an AC signal on the shield flowing because of the ground difference potential, you'll hear a hum. Breaking the safety ground of one of the two devices removes the potential and the path for the unwanted signal flow...

Exactly the same situation can occur, except usually worse, when you introduce a new ground into the system from cable TV or a satellite. Their ground on the shield may possess a different potential than the ground in your system and current will flow in all the interconnects. Usually by centralizing and bonding all external grounds to the common house ground you're at least giving yourself the best chance of reducing this problem....

Anyway, getting back to your problem. If you decide to not use the cheater and want to track down the problem you have to start with a minimal system and build it up to find the cause.
If you have no hum with the single amp and its speakers, then you can hook your preamp up with a single set of interconnects, ensuring the preamp has no source components connected to it and that its plugged into the same receptacle as the power amp. If it doesn't hum, then add a single source component to the preamp with the same conditions. If this minimum system has no hum, and you usually plug the devices into different receptacles, then you can try and plug the preamp or source component into a different and check for hum.

Well, you can see where this is going. You must rebuild your entire system, starting with the noisy amp, until the buzz reappears and then figure out why that happened. This requires you to rip apart your entire system and rebuild it. You will find the source of the problem this way.

Do you see why people use cheaters...... 8O

brucek

[aud19]

The hum you were hearing is a ground loop hum in your electrical system likely caused by your cablevision feed in to your house. Removing the ground pin from the 1095's cable by using the cheater plug simple de-coupled the ground loop from your 1095, hence no more hum. There's nothing wrong with your 1095 it's just happens to be a design sensitive to ground loop hums. The ground loop is what needs fixing in other words, not the amp.

Jason

[greggz]

I could have saved you the 53 cents. You take a pair of pliers and just yank the ground pin out of the cord. :B

But, I agree with brucek, the better solution is to track down source of the hum and correct it.

[Kevin P]

Try removing the cheater plug and disconnect the cable TV or satellite cable and see if you still get a hum. If the hum stops, then the problem is improper grounding of the cable or satellite at its point of entry into the house. If cable, have the cable company come and fix the grounding. You can also get an isolator that connects into the cable line, which breaks the ground loop.

[dedepas8]

I noticed my brand new 1098 come with two prong power plug and i have no buzz in my setup. I wonder if they do it deliberately to eliminated this buzz.

[Mark_C.]

By no means is a cheater plug a solution to a ground loop problem. Take your system apart piece by piece, starting with your cable or satellite, and track it down.

[David Meek]

Brad,

I'm not sure if you have lightning storms up there, but one single strike too close to your home and it could be "adios" to your 1095. Don't take that kind of chance - get rid of the cheater ASAP.

[ekkoville]

As mentioned, I used the cheater plug and all is well. But before that, I disassembled the entire system and found that the buzz was coming from any componet that was connected to the TV. The TV was, I think, connected to the cable from the wall. The TV or the cable was the cause, but at that point I went with the cheater plug. Also, my wife in and engineer for the FAA in electronic communications, and many coworkers use choker plugs, ie magnets, on power cords to eliminate noise and such. Some of them have said that may work, but it doesn't solve any inherent loop problems.

Erik

[hoofhearted]

ground loop hum + (plus) ground wire = silence

I had a ground problem with my rb 1090 humming with interconnects from the rx 1050 (rotel receiver used for tuner) to my RC 1090 preamp. Not wanting to use a cheater plug on the beast I decided to try the opposite and added a wire from the wall outlet plate screw to the ground screw for the phono section of the receiver. I did a search for info on hums and do not remember seeing much about adding grounds. I'm sure people are doing it and just not explaining it. Question for those who know is it a matter of taking the potenial that would run though the interconnect and directing to the electric circuit ground direct?
Try it you may like it !!!

[KEF]

Similar problem here

I moved into a new home and it took a while for the cable company to get my cable pulled to the house.

Prior to actually having TV, my RCD-1072, RB-1080 and N804s were silent; the minute I hooked the cable up to the TV, the hum started. I was less than happy to say the least -

I added a Tributaries Ground Guard (about $99) on the cable line to the TV and the hum was completely eliminated...

It is worth a try IMO.

Cheers,
Keith

[will1066]

I solved my cable-TV-based ground hum dilemma similarly with a Jensen VRD-1FF ground isolator.

[brucek]

One of the things that's important to remember is that these cable isolation devices (like the Mondial MAGIC cable TV isolator) are not compatible with satellite systems. They work wonders (albeit ridiculously overpriced) for cable TV ground loops, but will not work on satellite.

This is simply because satellite system use the RG6 cable to feed DC voltage to the LNB amplifier in the antenna horn. If you break the ground (as a cable isolator will do), then you can't power your antenna horn amp.

This make satellite ground loops a little more difficult to solve. The usual problem with sat systems is that they've been installed by a company that didn't bother to bond the antenna ground rod to the house ground system. This creates the loop when the satellite RG6 comes in contact with the house power ground at your HT system......... :E

brucek

[jimmyp58]

Also with some of the ground isolators, they'll block out some digital channels. You might need to check with your cable company regarding the broadcast frequencies.