buzz/hum...my first impressions, and some minor issues

Received my 990 on the 24th , but was not able to install/setup until Friday, the 27th...needed to wait for two crown amps to arrive to power the surrounds and rear surrounds. Was using a yamaha 5760 and two crown amps to power the fronts and center before reading about the 990.... dvi switching is what ultimately made me decide to give the outlaw a try, have a projector ceiling mounted and prewired a dvi and component cable from mount point to rack as part of home theater design....since the HD output of the Direct Tv HD receiver was using the dvi cable the 990 would allow me to start using dvi with a dvd player. The first thing noticed was I could hear a lot more details in movie tracks with the 990 compared to the 5760, I also preferred the sound....hard to describe, more details at low volumes, and easier to listen to at high volumes...don't know maybe this is what people describe as "warm". The first 3 times I ran auto setup it would go through the tests, then fail saying the fronts were small and surrounds were large, try swapping them...not sure why it detected this, truth is opposite, but after I powered down and tried one more time, it seemed to work fine. One minor issue I have is that the remote button to change surround formats only goes in 1 direction, if you toggle between DPLiix-movie and DPLiix-music, to get back you need to cycle through all the other formats...like I said minor. Also, as others stated, having the setup menu on the front panel would be nice....especially for those who use projectors, found myself wishing I did not have to turn on the projector each time I wanted to use the setup menu. Last night decided to give dvi switching a go, and ran into my first "real" problem...though it is probably not a 990 problem. I found that when using dvi switching all channels had a distinct hum when at low volumes or when selecting an unused input. Had read about ground loops before (though never heard hums with the yamaha), so after reading and troubleshooting, found two culprits....first the obvious..sat coax cable, was able to get rid of this by running the cable through the coax in/out on my power strip, the second problem, was a little more challanging to find. Turns out since the projector is ceiling mounted, and using an outlet created for it on the ceiling, it must not be on the same circuit as the rest of the a/v equipment. When I unplug the projector, hum goes away...also if I run an extension from the projector to the second outlet of the box the a/v gear is plugged into, no hum. If I decide to keep the 990 looks like I will have to run a power cable down to the a/v outlet..I know it can be covered and painted the same color as ceiling/wall, but since I knew this room would be the theater room, had everything prewired/run to keep as clean as possible. Need to test more today to verify connecting projector to a/v outlet gets rid of hum. Anyone else deal with this before, and have another solution to running a long power cable.

Thanks,

John

I have a front ceiling mount Sony HT, with its own outlet. I sometimes pick up a faint hum. I found that when I have the theater room lighting very dim, this is when I can hear the slight hum. When the lights are turned all the way up, nothing. With the lights off, nothing. You might want to check this out in your own theater room. See if what you are hearing might be coming from your room lighting or might be caused by the dimer controls in the wall that are remote controlled.

Thanks for the suggestion Dobeman, but tested without any lights on, and once the projector is plugged in get the hum....btw the hum is not loud, but can be heard while seated if an unused input is selected, or if using very low volumes on an active input. Tonight I watched the Heat/Pistons game with the projector plugged into the a/v outlet, and no hum/buzz. Tomorrow will test the dvd player, and if no hum, then off to home depot to get something to mount the power cord and extension on the ceiling and wall. I have a Panasonic ae700, and have to unplug the power cord after each use (prevents vb lcd panel distortion)....was thinking of either running an extension to an easier accessed outlet (need to use a ladder now) or some type of remote cutoff for the a/c of the projector..the 990 hum/buzz issue just gives me another reason to run the power line.

You may have a ground loop problem . You said you were watching the Pistons Heat game and there was a hum . So I take it you have cable or sat. hooked up to it some how or another . Try unhooking the coaxial cable coming in from the wall outlet . You know the cheap screw on connector . If you do have this type of connection through a cable box or sat. rec. it is often the culprit . If this is the source of the problem you may need a ground loop isolator .

check the link

http://www.mitcables.com/products/products.asp
( search for ISO-LinQ must be spelled this way )

http://www.elect-spec.com/video.html

I have the same problem with the auto setup - it fails saying my surrounds are large and my fronts are small. My surrounds and fronts are actually identical (small). I tried disconnecting my backs since they are different w/ a different frequency range, but it still failed. I tried activating the x-over on my sub thinking maybe that was throwing it off, but it still failed. One thing I noticed while the auto setup was doing its thing, it was setting the delays correctly, but the trims were way out of whack, compared to me doing it manually w/an SPL meter. I even tried orienting the mic vertically, facing back wall, front wall, etc, to no avail. Not a big deal but still kind of weird.

1) On the auto setup. The SUB needs to have an 80Hz cuttoff or the calibration fails. You can turn it up after you calibrate. I think this message about fronts being small should really say that the sub seems to be a full range speaker. Wrong message assigned to the error check.

2) Ground loops. I have dealt with this extensively as I have tons of wires going all over my house. The secret to thinking this through is that you get to pick one point as ground, not two. In my case that is the power plug at the projector.

I ran some romex down to the audio equipment from the same circuit as the projector. I was getting audio and video hum. The video hum was faint rolling bars that go down the screen slowly.

Next, I ran a wire from that ground point to ground all the antenna leads that come into the house. Both the off the air and the satellite are grounded to this same reference. Use these RF ground blocks and run a wire to the point you are calling fround.

Next, anything that goes off to another room and will by necessity be grounded there gets its ground broken and a little ground isolator composed of a couple of capacitors (one in the center conductor and one in the ground). This includes RF and SPD/IF connections.

Before I did this, the antenna lead to my daughters room would cause hum.

You can disconect leads one at a time but you may not have to isolate as many leads if you pick your ground reference correctly.

Rance,

I am trying to remember...think that after I wrote down the distance and trim values, then manually put them in for the configuration, is when auto setup quit failing with the front/surround issue. Maybe the default values before running a setup are what is causing the problem. Another thing that initially confused me...the trim values listed in auto setup, must be how far from the desired level each speaker is at. After auto setup worked, and I saved the values, the trims were the negative of what auto setup listed during the test, e.g. the +3 db listed for my sub, actually set the trim at -3 db after the auto setup config was saved. All non 0 db trims were saved like this. Could this be why your SPL meter values were so different?

mm_half3,
I actually had configured the channels manually before trying the auto setup, so its not the default values throwing it off. I think you're right about the values displayed prior to the save however, because now that I think about it, they were just about the inverse of what I had set manually.
I thought that the sub may have been throwing it off and that is why I had set the x-over at the sub around 100, 80 and even 40, but got the same message.
Like I said, its not a big deal, but I'll probably continue to fool around with it.
Thanks for the input.

The readings in auto setup are the output of the channel. So, if the channel is -4dB, you would need to set the trim to +4dB to compensate.

Looks like I am stuck either running a power cord down to the socket the a/v gear is connected to, or running wire connecting the two outlets, so they are grounded the same (if I read bigal's post correctly)...either way adds visible cable runs, since access to them in the attic is not very good.

Running a wire may or may not help given that both outlets are persently grounded already. It would help if you float the outlet at one end and substitute the ground that you ran from the other end (your one ground reference). Running an extension cord is more certain.

If any of your equipment has a 2 wire plug, try reversing it. That is required for my sub to avoid hum.

But please remember that playing with AC wiring is a job for someone who knows what they are doing. Fooling with grounds and running AC wiring is not for the faint of heart -- unless you happen to have an electrician's licence! I'd hate to see an Outlaw cause a fire or cause a safety hazard rather than diagnose the problem and then call in someone to deal with the wiring.

I don't think I was clear and should clarify. I was talking about buying one of the adaptors made for doing just what I am suggesting. The ones that take a 3 prong plug on one side and 2 prongs and a green wire with a lug on the other end. The green wire is susposed to be connected to a ground. I was just suggesting getting that ground from across the room. Also, you should not plug anything in until all the grounds are securely connected.

I would strongly advise against opening the outlet box and fooling with the wires inside.

Thanks for the suggestions, I think I am going to extend the power cord from the ceiling to the outlet by the a/v gear. Getting both outlets to use the same ground requires me to run wire also, so I might as well make disconnecting power to the projector easier in the process...now just need to find a cheap source for a 12 ft cloverleaf power crd (like many laptops use), or a C5 to C13 adpater so I can use a regular computer power cord, and adapat it to the cloverleaf at the projector. A regular extension cord won't work beacuase the plug portion of the extension won't fit in the plastic cover used to conceal the cord.

All the grounds in your house wiring end on the same bus bar in your panel! The adaptors or "cheaters" have a green loop on them where you are supposed to screw the plate cover screw to ground them for a correct installation. If you kill the circuit you can pull the outlet out of the box and verify the ground wire is still connected. The other thig is to go into the electrical panel and carefully check and make sure the ground connections are tight. The panel ground is supposed to be wired to the water pipe, in older installations, and in newer installations the water pipe and a ground rod. Jim

So are you saying you think the buzz/hum might be because the ground on the outlet in the ceiling for the projector no longer has the ground wire connected, or that maybe even the panel in the fuse box for the circuit has the ground disconnected? I thought it was typical for people to have these problems when audio/video devices were connected via video/audio cables, and their power connections were not on the same circuit. If all the grounds are connected and all the circuits of the fuse box are connected to the same ground, is the problem still a "ground loop", or more because of using different wires to get to ground.

Ground Loops are tough to ferret out!!! As an electrician I'm letting you know where I'd start. I tseems to me in most cases ground loops are caused by interference placed on signal cables. I.d check the grounds as stated to eliminate the ground ware as the culprit. I've seen waires installed on the ground bar looking like they were placed correctly only to find out they were resting behind the ground bus!

I've also seen where it is a faulty piece of equipment injecting the noise on the signal wires. Jim

The $3 solution to check the outlet's ground: go to Lowes/HD and but one of the plug-sized circuit testers that plugs into the outlet and has three lights on it. If the lights that come on when you plug it in match the "open ground" diagram on the tester, you need to have an electrician check the ground connection.

What sluggo said.

About three years ago I solved the slight hum problem by properly grounding of my Comcast cable lead-in cable.