Hello
I am getting a slight hum in my 7700. It is not always there and I have discussed this issue with Scott. It started last winter. In the summertime there was no hum at all. The hum is definitely from the 7700 and not from my speakers. I am using six of the 7 channels and all of them are working. The noise is only noticeable when I turn on the 990/7700 and so small that I have to put my ears close to the 7700 to hear it. (2'). I was wondering if anyone had any thoughts as to what this noise could be.
Scott thought that it had something more to do with the power lines or surge of more power coming thru the electrical lines at different times of the year rather than something being wrong with the init. I have rewired everything. The 7700 is plugged into its own line with a receptacle from tributaries. I do have a ground line connected to the 990 that I was thinking of disconnecting. I am using a Furman surge protector but the 7700 is NOT plugged into it.

I am also in the next month or two going to purchase the Marantz 7701 processor and of course will be doing an entire rewire.

Ant ideas? Thanks

I would agree with Scott...
I have the same situation, at times, with my 7500. Its been like that since day one (2005-6); When I first noticed it, I had tried everything to track it down. I also had talked to Support about it. Never came up with a definitive answer except that, yes, it could be power transmission to my house.
The hum appears to happen at very busy times of the day (suppertime, early morning)...it may last 10 minutes, or 10 seconds...it is a very weird, BUT almost predictable pattern.
Like you indicated, it is not loud, i.e., I have to be near the amp to hear it. I hate to admit it, but I kind of just live/or base my HT/music episodes with the hum.....but as indicated, it is a very sporadic occurrence.
Not because of this incident, but soon a friend of mine is going to do a more thorough re-wire of my HT room (dedicated circuits, more receptacles, etc); like you, I plan on doing an upgrade of my preamp.

Power companies try to control load voltage in a very tight band. However as load is increased on the system the voltage tends to sag somewhat although it never goes too low. It is possible to locally (neighborhood area) to sag the voltage low enough to cause some issues. Your power conditioner should eliminate this slight fluctuation within reason. If the voltage fluctuates more than the conditioner can handle you should get some sort of light or beep. My APC does both and it locks in the light so I can tell it had a transient if I am not right there. Get a volt meter and check the voltage to the house when the problem occurs. Leave it connected and watch the value when the problem occurs. This might not be conclusive since the system operators are constantly striving to return the voltage to band. Bear in mind the same local fluctuation can occur inside your house if the power panel is insufficiently sized or you are running a large load demand (dryer plus oven/stove plus air conditioning/heating).

Thanks to both of you.
I will borrow a volt meter XM but could you tell me what am looking for in numbers? Sorry but I never had a use for a volt meter. My electrical circuit breaker box was rewired and updated about five years ago and since that time I did add two 20 amp circuit breakers to the HT room b/c I was thinking about a future update for my amplifier...the 7900. I never purchased the 7900. My electrician assured me that i could install the additional 20 amp breakers and more if I wanted.

The hum is constant. Low but constant. Yet, during the spring and summer non-existent.

Thanks again

Just to be clear, if the issue is becuase of "sag" in the delivery of power (which it likely is if it is related to load for the whole service area at different times of the day...) re-wiring will not do anything to help. What MIGHT help address this is a very substantial "power conditioner" -- typically you would probably want something that is capable of not just "bringing up the voltage" for the amp but with enough capacity to also help keep the rest of your electronics from suffering.

I have experinced commercial PA amps doing an "audible resonance" type buzz when the line voltage is signficantly below specification and have used a "variac" which is a specialized kind of transformer that can "dial up" the voltage in such conditions. Unfortunately I don't know if these are really the best solution for a home theatre as they can be rather ugly ...

Your incoming house voltage should always be more than 220 volt. It is typically around 235 or so. You should always have more than 110 volts at your receptacles. It is typically around 117 vac. I would doubt if the voltage is dipping enough to challenge your equipment as the 7700 has a pretty good power supply of its own. I would start looking for a mechanical reason for the hum such as loose feet or a loose cabinet screw. It is possible that the cabinet temperature changes just enough during the year to cause something to be less than tight. Make sure your cabinet is also not the source from loose stuff. A mechanics stethoscope is very helpful in locating mechanical vibrations.

Thanks again.
I do not have my equipment in cabinets. The equipment is on glass shelves that can support over 100 lbs. My conditioner is a Furman Elite and the amp is not plugged into the Furman per Outlaw specs with the amp.

I guess for now I have done everything except to check the voltage and since I will be purchasing a new processor I will wait for any rewiring.

Thanks for the suggestions and I will get back to guys as soon as I connect the Marantz.

I understand the glass shelves can hold the weight but are all the amps feet making solid contact. If one isn't solid it could cause a vibration. Also check your shelves. I had a small piece of wire strip insulation get between the shelf and the ledge it sits on and give me a vibration at low frequency. I finally found it with a test disc and a mechanics stethoscope.

Yes XM all four feet are firmly planted on the shelf. The hum is definitely coming from inside the 7700. To the far right of the cabinet.
I do appreciate your advice about the volt meter and I intend to look into that as it might be the problem. A good friend of mine decided to go to Hawaii over the holidays and is retuning on the 8th. He has a volt meter.
Also the new processor I intend on purchasing is the main reason that I am not doing anything more aggressive at this time.

INPUT NEEDED ON....Processor. I am considering the Marantz 7701. I like everything about it. It does have a few more bells and whistle on it compared to the 7005 but not at a gouging price point. I can grab one for $1600 and trade in my Outlaw for $300...leaving me with a $1300.00 price tag.
Outlaw is selling the 7705 for $1200 plus shipping and they are out of stock.
No, I do not need this processor tomorrow but there is no mention about when or if Outlaw will be still offering the 7005.
Hmm maybe they will be upgrading to the 7701?
What would you consider to be the best move that I should make.

Thanks

At $1300 it would be hard to beat the 7701. It is also more future proof since it can not only pass 3D but also the possible 4K video in the future. I would definitely take the 7701 since the price is about the same.

As far as your 7700 hum have you considered taking the top off and trying to find a loose part inside the cabinet. The 7700 has seven channels in the same size box as the 7500 so there is less room inside. Maybe a cooling fin or loose chassis screw is causing your hum. Have you tried disconnecting the channels one at a time from both input and output to see if it is related to a single channel.