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.

I have not tried either suggestion XM.
I will attempt to disconnect as you said input and output.
I am a little nervous about taking the cover off the 7700. Is it a simple task? Any tricks to putting it back on? I am sure you have heard that it is "easy to take something apart but to put it togather is another".
I won't have the time to do all of this until Monday.
What should I look after I take the over off?
When disconnecting the inputs and outputs if I find the noise stops what then?

Thanks a lot XM for your help and patience. This issue is really frustrates me. Otis so small but so annoying.

Frank

First go to Autozone and borrow or buy a mechanics stethoscope. It is basically a set of earphones connected to tubing which connects to a probe. Cost is like $10. This will help you localize the hum to a specific area of the amp. The cover is held on by several screws and when they are out you can just slide it off the top and remove it. Make sure the amp is unplugged for an hour or so before you take the cover off. Once the cover is off do a visual inspection to see if it is something obvious. If nothing is found then use a nonconductive probe to genttly push around things like heat sinks circuit boards and other hard mounted items. Don't poke at anything soldered to the circuit boards and do everything gently. If you want to see what it looks like before you remove the cover there are some pictures of the amp without the cover on the forum somewhere. I will try to find them.

With your system off, disconnect one channels input and output and then turn the system on to see if the hum is still there. If it is turn the system off and then move to the next channel.

Here is a link that Gonk made a while back to pictures of the inside of the 7500 amp. The 7700 is likely going to look like the 7500 but without the space between channels. Sorry could not find any of the 7700 but Outlaw used to post pictures of the inside on the site. Ask them if they have any of the 7700. Bear in mind that your amp is still under warranty and a call to Outlaw may be helpful. I have read about the mechanical hum on the forum before so they may have some ideas.

http://www.prillaman.net/outlaw_pics/

XM
Thanks for all of the tips.
I WILL DO EXACTLY as you say and follow your instructions. I most likely will be doing this on Monday of next week. I will get back to you via this forum by Tuesday and hopefully I can tell you I found and solved the problem.
If I do find the problem by doing what you have suggested I will owe you a beer!
Ugh that amp is so heavy!
Thanks again
And please check the forum on Monday or Tuesday for the results.

PS I don't believe the amp is still under warranty. It's better than five years that I have had it.

Well if the amp is not under warranty more reason to BFC!!

Absolutely!!
Yesterday and today...no hum!
Last night...hum?!!
WTF.

Normally I would not think of electronic equipment, which does have any moving parts, as being subject to vibration but.. transformers are known to hum sometimes. It could be a loose mounting screw or an isolator that is not performing well. The transformers in these amps are very large and need to serious mounting hardware so it is possible that is the issue. Once you get the cover off and do your inspection, if you don't find the issue, I would plug it in and let it sit until the noise starts and see if you can physically locate it. Obviously this will require some care on your part but if it finds the issue then you have a chance to fix it. If the transformer is humming you should be able to easily find it just by touching the external insulated portion and feeling the vibration. Pushing on them a little might cause the hum to change if it is a mounting issue. If it not the transformers then touch the heat sinks on each channel and lightly push them a little to see if the hum changes. Good luck and be careful.

Transformer hum is usually caused by core delamination. Unfortunately it will only get worse, if this is the problem. I'm getting a little hum on my 7075 and it sounds like transformer buzz to me. I haven't opened it up yet though to confirm. The only real solution is to replace the transform. Check for loose mechnicals first. The transformer looks expensive.

Note: This assumes the core is laminated iron rather than compressed ferrite. If it's a solid ferrite core then the problem is something else.

Thanks
No hum all day yesterday. Today I am rather busy but I at least intend to disconnect the inputs and outputs. Tomorrow is another day and I will take the cover off....cautiously.

Just finished disconnecting the inputs and outputs from the 990 and 7700. Just in case I also disconnected the speaker cables to the amp.
I disconnected each cable one at a time turning on and off the 990 and 7700.
End result was that the hum is still alive. I also checked ALL of my other connections to make sure they were correct and tight.

I have a couple of options.
Input is appreciated.

First, I can disconnect the amp take the cover off like XM suggested and take a look to see if there is anything visibly lose and perhaps use something like a pencil to prod around the guts of the amp.

Second, There is a electronic repair shop not to far from me that over the years has done repair work on a Yamaha receiver and recently did some work on my ten year old Sony 777. He is very reputable. Since the unit is out of warranty it would save me the shipping and handling fees as well as not worrying that the unit could sustain more damage thru shipping. As you know the unit is 93lbs.

Third, I could do nothing and when the unit on channel stops working take action to repair it at that time. The hum as I have mention does not interfere with the enjoyment of listening to music or watching a movie.
What if the idea that the voltage in out out of the house is the issue? Then I waste my time and money bringing into the shop.

Thanks guys and looking forward to a response.

Is there a chance you could bring the amp to a friend's/ relative's house for testing purposes??

As I have mentioned in other posts, I have had amp hum at certain times of the day...all told, maybe about 1% of my listening or TV viewing (and its at a very predictable time of the day-I sometimes go week's at a time without hum). When I first bought the 7500, I tried everything to track it down..no luck. Who knows, the frequency of it happening since then has greatly diminished. I know another time when the hum reappeared, it turned out to be a faulty old desk lamp that must of been on the same circuit.
As I said in other post, I really believe it originates with the power grid (its a very old neighborhood/no upgrades in line transmission).
I do have DIRECTV; there is a ground wire outside the house, i.e., that I would assume there is a ground rod associated with that wire.

I would really try and move the amp to another location for testing purposes.....

I would do the inspection at least to get an idea of the scope of the repair. I saw a review of a Yamaha Aventage reciever and they wrote about Yamaha installing a fifth foot under their torroidal transformer because the weight was a concern. Maybe you could temporarily install a piece of wood or rubber of the correct thickness to prop up the middle under the transformers.

Up early today
Just uncovered the 7700.
Pretty cool!
Wish I knew what I was looking at haha. Have to lighten up a bit.
I did what i would call routine inspection and did not fine any LOSE parts.

I called the electronic repair shop that I have dealt with previously and spoke to the owner about my problem. Off course he did reccomend NOT doing my inspection saying I could make matters worse. I am bringing it in today. He told me he will be able to evaluate the 7700 this week maybe Thursday. On the phone he told me it sounds like a power source problem but he would have to look at it.
I am bummed especially if I do not get this back in time for the Super Bowl. Unfortunately it is out of my hands.
I will get back to everyone as soon as I get any updates.

I do appreciate everyone's input on this subject and I really was hoping to fine the problem myself.

Does anyone know if it is a part issue can the service shop get parts from Outlaw and if not would they be able to get the same quality parts from somewhere else?

Thanks

If it's a part issue and the the shop is a good as you say then they should be able to pull the part number off the offending part and get the exact replacement from a distributor or, in some instances, directly from the manufacturer.

Unless it's a custom part with a sole source agreement, of course...

The likely direct source of parts would be ATI since they built the amp for Outlaw. Keep us posted as to progress and what the shop finds. I had my 7125 repaired by Outlaw several years ago and it was back within 10 days. Your local shop should be able to match that I would think.

Just dropped the monster (7700) off at 12:30 EST. They said they should be able to look at it tomorrow. I asked for the chances of it being fixed by Super Bowl Sunday and they said I should have it "way before that".
We will see.
I will kept you guys up to date.
I am really curious as to what the problem is with the 7700. Just as anxious to hear that information as I am to getting the amp back and on-line.

Hopefully it is something simple. If it is a delaminated transformer core it should be a simple repair. Did you ever notice any noise in your speakers?

No XM. The humming was strictly from the speaker.
I am hoping that I hear from the repair shop by tomorrow since he said he would probably be evaluating it today.

RS did you mean strictly from the amp?

Sorry XM.
I just saw this.
The hum was strictly from the AMP.
They have had the 7700 since Tuesday at 10 am. They told me that they would for sure be evaluating it the next day (Wednesday). This is Friday and I have not heard anything. I intend to speak to them today at High Noon.

Will keep you in the loop.
Thank you for your interest.

XM
I could not wait and so I called about the 7700.
The mechanic's name is Frank. He told me that the 7700 has been running two days on and off. No noise. He ask me if I had the unit plugged into any other device such as a line or surge protector.
I said no that it was plugged directly into a wall outlet.
He intends to take a look at it internally later today.

Now I am really scratching my head.
Could it be the outlet?
The only other thing I can think of is that I do have a ground wire (that is not in use) right beside the amp. I have been to lazy to take it out of the PVC I have it running thru but it is laying very close to the amp.
I am going to work on it right now.

XM
There were two ground wires. One I just removed but the other one was from the 990 and I noticed it was disconnected. Could that have been the issue?

Sorry for all of these posts.
I just remember that I had the ground for the 990 disconnected b/c if I remember correctly I had a ground loop with it connected to the 990.

Going crazy.
Thanks...from the lunitic.

Don't get crazy...I think we all become anal about our systems; I know that I've have been super-sensitive about ground loop issues because it is a major bugaboo with high-end systems....and I originally had problems with it when I first set up my 990/7500 combo years ago.
As I've said several times in different posts on the Saloon, I'm pretty sure my amp "hum" issues are related to incoming power from the electric company "Grid". Lately, I have had no issues at all, for like 2 weeks. When I do get them, it is at a certain time of day (supper-time), and lasts intermittently for about an hour. That's it...everything is dead silent after that, for days on end. Although I did have an issue recently, and it turned out to be an old lamp, with a weird kind of bulb that was in another room (not even on the same circuit!).
In my eyes, these Outlaw amps are bullet-proof...I really believe your amp hum issue is a grounding/electricity thing; are you sure the Comcast line coming in is properly grounded?

If he doesn't find the problem, when you get it home plug it in and let it sit completely by itself for several days and listen for the hum. If no hum it is something else in your system. Sometimes it is hard to localize the hum and I find it useful to touch my stuff to feel if I can find the source. The same goes for speakers. Lightly touching the cones is more reliable than your ears as a gage.

Thanks guys for all of your support.
I must have made at least four phone calls to the poor guy who is monitoring the 7700. I had contacted Scott on more than one occasion about this issue and as you mentioned (jmacari) Scott referred to the issue as being the power grid at different times of the day and I imagine different times of the year. I believe that I had mentioned that up until recently there was no hum. I did have this issue last year but again at different times of the day and season. Sounds crazy but true. I had disconnected my entire system TWICE to find the culprit but only found myself to be more frustrated.

Comcast is connected both to a grounding rod six feet in the ground and also is plugged into my Furman. As far as I know this setup is correct. If not please tell me.

I will take your advice XM and plug the 7700 into an outlet and turn it on for a couple of hours and see what happens. I can also after I am satisfied that the 7700 standing alone is not humming reconnect the speaker wires and the balanced cables and then one at a time disconnect the rest of the equipment from the Furman.

I did ask Frank (repair man) if the issue could be from a bad receptacle but he said as long as the receptacle is wired correctly it would be a none issue. Receptacles work or they do not.

Will keep you up to date.

If the recptacle or its circuit is not going to the same ground plane as your 7700 it could be the problem. Try plugging into a separate circuit using an extension cord. I would also try removing the comcast feed to your system.

I started looking into my hum issues and have noticed a couple things that I'll post here in case they help others.

1. I started cleaning off my workbench so I could open up the amp and noticed something was making the same sounding buzz as my amp. turned out to be one of the compact flourescent lights in my shop. Turning off all CFLs in the house didn't make a difference so I started thinking there's noise on my power lines.

2. I built an RF sniffer probe and started poking around my system to see if there was any radiated noise.
Power lines : Nothing
975: Nothing
Amp: BUZZZZZZZ
I looked at the amp and the noise peaks out when the probe is by the transformer.

Conclusions: None. But either there's noise coming in through my power lines. (This is called conducted noise.) Or something is going on in the amp that is generation the noise. I need to do more exploring. I'm going to try a filter on the power input and see if that helps.

Here's how I made my test probe:

I took an old RCA cable and cut the connector off one end. I then stripped off about 5 inches of the outer insulation to expose the shield. I twisted the shield up and cut it to about 3/4". I then stipped about 3/4" of insulation off the center conductor. Loop the end you just stripped around and twist it with the shield. A little solder and a little tape and you have test probe with an RCA connector on the end. Make the opening created by the center conductor loop into roughly a circle.

To use it I disconnected the RCA connector comming from the 975 and plugged the probe into the RCA input of the amp. Use the probe like a butterfly net (only slower). The opening of the loop needs to face the direction you are measuring. I had the kid listen to the speakers as I move the probe around. She would let me know when the noise got louder or quieter.

Will do XM.
Tuesday will be a week. I will be calling about the 7700 early morning.
I do not think anything is wrong with the 7700.

Thanks EE

Ok...Today I called Frank about the 7700 at High Noon. He has had the 7700 since last Tuesday and has the amp on and off now since last Wednesday. He also did a routine inspection of the guts of the unit and found absolutely nothing wrong. His response about me asking about the inspection was that iI have a very well built amp. On my end I have made routine checks on all of my circuits with a meter that indicates if the receptacle is wired properly. I have a clean bill of health on the receptacles. Besides Frank told me that would be a non-issue with the problem I am experiencing. He wanted to keep the 7700 for one more day and since I was unable to pick it up today he is running it again for most of the workday.
Tomorrow I will be picking the up the 7700. I will be checking every piece of wire, connections and cable. I do intend to first disconnect the Comcast cable and take it from there.

So people wish me luck.
One more thing. If the cause IS from the Comcast cable what do I do to prevent the problem?

PS I will be unable to work on this until Friday. I do intend to work at it all day if I have too.
I will report on the update Friday at 5.

Thanks people!

If there is no hum with the cable box DISCONNECTED from everything in your audio/HT loop, then all is well with your equipment, i.e., it is the cable TV stuff. Make sure the cable coming in from the pole is grounded; if not, call your cable company and tell them your situation...I've read that it is their responsibility from the local PUC/building code, etc., to ground their equipment when entering a home. Also, check out the other thread-
http://ubb.outlawaudio.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=92252&page=3

Hello People,
The frustration gets better.
I picked up the 7700 yesterday. It had been running on and off for eight days and there was no hum.
Today I just connected the 7700 to the outlet. HUM.
I did disconnect my cable service. HUM
I checked my circuit breaker box looking for any lose wire. No luck.
The last thing I did having some success and I am hoping that someone here on the Forum can give me good advice. I have a 50' extension cable...three prong and first I plugged the extension cord in a bathroom outlet twenty feet away.
NO HUM.
Next I used the same extension cable and plugged it into the same outlet as I would plug the 7700 into. NO HUM.

Great, right? How do I solve this problem? Better yet. What is the problem? I certainly do not want to have a 50' extension cord in the loop. I do not have a shorter extension cord (10') to see if that would work but I intend tomorrow to borrow one and see what happens. I do not know if they made a 10' heavy duty extension cord.

I spoke to Scott and he was his usually self...helpful. He admitted he did not want to offer any advice b/c he really was not sure what the problem could be. He said he would get back to me as soon as he speaks to one of the engineers who work on the 7700. It is almost 5pm out here in Pennsylvania so I do not think that Scott will be calling tonight.

In the meantime if anyone out there can explain to me what the issue is and how to solve it PLEASE let me know.

Thanks guys

It sure sounds like that circuit is not too well...it may be time to call an electrician. If it's good off an extension cord, then find out what breaker (in your main panel) that plug is connected to; I would assume it is a different circuit then the one the amp was originally connected from. It may be there are too many appliances/equipment, lights, etc. on one circuit and causing problems....like I said, I would call an electrician to further investigate....

I mentioned it somewhere here in the Saloon recently about a hum problem I had.....I had an old lamp with a very unique bulb in it; it was in a room in another part of the house....I noticed a hum in my amp for a few days; for the life of me, I could not figure where in my HT system it was happening, until one day, my girlfriend walks into the other room ( I was sitting in my HT room with nothing playing) shuts this light off.. AND THE HUM DISAPEARS...suffice it to say, I was overjoyed!!! (because amp hums can drive us nuts, LOL)...long story short, is this lamp holds sentimental value for us, but WHEN in HT mode, the lamp is turned off....

Thanks for your opinion. However I have a dedicated HT room and all circuits in that room are prioritized specifically FOR that room. There are no appliances. All of the equipment is connected to a Furman line conditioner except for the 7700. I have four different circuits that I use for my equipment. I have two 20amp circuits and two 15amp circuits.
All circuits were tested for correct wiring. No problems.

I tried all circuits without the extension cord getting the dang HUM. I also tried all circuits using the extension cord and everything is quiet as a mouse.

What are the chances that all four circuits breakers are bad, highly doubtful with this scenario.

Thanks for the advice. I might be forced to bring in an electrician but for now I want to try and solve this problem myself with a little help from my friends.

Thanks again

The only effect a long extension should have is to lower the voltage slightly to the 7700. I guess it is possible that the plug on the 7700 fits better to the extension cord than to the receptacle. I would check out the plug on the 7700 to make sure it is fitting tightly to the receptacle and that all the connectors are clean and shiny.

Thanks XM
I have tried everything you suggested...to no avail.
Tomorrow I might physically check the receptacles but what are the chances that both 15 amp circuits and 20 amp are malfunctioning?
Maybe Scott was right all along with this about at different times of the day and different times of the year the voltage is different coming into the house.

Personally I don't buy the voltage fluctuation thing. Voltage would have to vary quite a bit to affect the amps power supply. Voltage and frequency are very tightly controlled by the power company. When the hum starts in the evening do you notice a change in the intensity of your lighting or anything like that. Could the power cord to the 7700 have been damaged at all. Can you try another cord. You may be able to borrow one from the guy that worked on your amp.

I don't really believe in the high voltage thing either. I guess I am getting desperate and more frustrated.
I have two power cords XM. One is the original power cord I got with the 7700. The other cord is a power cord from Tributaries that I pick up cheap fro a friend of mine. I did interchange cables trying to solve this problem.
I might touch base with an electrician.
The thing that really puzzles me is four different circuits and the same results.

Have you connected the 7700 to the power conditioner to see if that helps? Here is a long shot. Try leaving the 7700 on and one by opening each of the breakers in your main power panel (except of course the ones feeding the 7700) including the 220 volt breakers. At this point since we have kind of ruled out the 7700 it has to be something upstream. Maybe some load on your power panel is causing a feedback to the panel. If the noise stops, then reclose that breaker and continue the process to make sure there are not two issues. If you find that the noise stops then figure out what is on that breaker and unplug it/them one at a time.

I have connected the 7700 to the line conditioner..no luck.
Your idea about checking the breakers I am doing today.
I have to say this is very trying.
Yesterday I noticed that when I used the 50' extension cord the hum was still there. Very low in volume but still there. It was so unnoticeable I had to put my ear to the basis of the 7700. This has me thinking that I wonder if the place I bought it to did not hear it. However I was there when it was running and I did not hear anything myself.
Thanks...I will be posting today's result later today or late morning. I have to get myself together before I start to look for anything.
A thought I have is I have an old Yamaha receiver. Only 100 watts. I wonder if I plug it into the outlet in my HT room if the HUM would be there? I don't know if that's the way to go.
I still have not heard from Scott but was talking to him yesterday and he wants to talk to one of their engineers who worked on the 7700. If nothing positive happens today I should hear from him by Monday , Tuesday.

Rubbersoul,

I left you a lengthy voice mail yesterday. Please check it for an update on my discussion with the engineer. He believes the power cord is serving as a filter for DC; the longer the extension cord, the lower your hum level. He's going to give me a method for properly measuring for DC on your AC line. There's a little more detail in the VM, and I'll be in touch again on Monday with more.

Scott

Based on what Scott said, a possible fix would be a one to one transformer between your receptacle and the amp. The DC would not pass the transformer. How DC is getting on your AC circuit is still a mystery.

Thanks Scott
I have not checked the my voicemail, sorry.
Thanks for listening and going the extra mile.
I hope you see this message Scott. I have a Drs. Appointment on Monday at 12;30. Please call me early or if that is not convenient...4pm.

Thanks again.

XM...I did what you said and there is nothing new to say. Hopefully Monday after talking to Scott the problem will be resolved.
Mystery is correct.

Fill me in XM. I know that AC means alternate current and DC means Direct current. Can you explain to me how this is affecting my system?

Thanks

The amps power supply is expecting AC which oscillates its signal at 60 hz. DC does not oscillate and may affect the amp because it adds noise to the circuit and some of the components respond differently to DC current vice AC current. I have seen AC get into a DC circuit because it can induce a current in wire but how DC gets into an AC circuit is beyond my electrical experience. EEMan may be better able to explain since I think he is an electrical engineer.

Thanks XM.
This issue is really disappointing to me that it has not been a quick fix. I have tried everything. The amp was serviced, the receptacles were doubled checked, I even took the cover off my circuit breaker panel and checked for lose wires, Checked the grounding rod outside the house, disconnected the balance cables and speaker wires as you suggested and the list goes on.
I spoke to two electricians and they both agreed that it is not a grounding issue. Unless my gauge was not working properly and even then he did not think a ground issue would not cause the hum in the amp but rather my speakers. Ground loop.

I hope when I speak to Scott on Monday there is a solution.

Thanks to everybody for their support and suggestions.

Ok 3:25pm EST
Turned the 990/7700 on to watch the NFC championship game between SF and Atlanta.

The amp is quiet as a mouse. No HUM.
Voltage, mild weather??!

I going to enjoy it today.

Here is an extensive article that might help explain how to test / correct for DC on the AC line -- http://sound.westhost.com/articles/xfmr-dc.htm#warn

Thanks renov8r,
On the road right now but will definitely check it out.
I am anxiously awaiting to hear what Outlaw's answer to the problem.

I have to say Scott is great with customer service.
Good man.

Most of the times what people are talking about is corruption of the 60Hz AC signal resulting in the average voltage being something other than 0 volts. Motors are prime corruption suspects. Why is this bad? Transformer core magnetization follows a curve called a hysteresis loop. If the AC signal stay symetrical around 0V then the loop stays centered around 0. If there is a DC offset on the AC signal then the loop will start moving away from zero towards saturation where buzzing is possible.
I never thought about this until this thread, but it makes a lot of sense and matches what I'm hearing in my system. I wonder if I need to invest in one of those power conditioners that output a pure 60Hz sine wave.

The hair dryer example in the link above is an interesting thought. I wonder if there are some devices in your home that do a similar thing with changing voltage in a similar way. A multi-speed blender, an eco friendly refrigerator or even a heat pump that varies speed based on load could be a culprit. Since the problem seems to be related to the time of year maybe your AC or heating system is causing an issue.

I once had to deal with a venue that had some decorative fountain / waterfall that was powered by a large pump. When that thing was running there so much voltage coming back to the sound system you'd swear the amp was physically dancing not just buzzing...

Maintenance guy finally got new pump and the problem went away.

Well guys I cant think of anything in the house that is constantly running that would create this problem.
Saying that is NOT to say that I do not understand where you are coming from. A hairdryer left on , florescent lights, I even thought it could be my heater since I was having trouble with that during the week.
No dice.
Like I had written on a previous post a week on soon ago I turn on a football game. I did not change anything. As a matter of fact I was expecting to hear the HUM. I turn on my cable and there was nothing coming out of the amp. It was dead quiet.

Will keep everyone up to date.
Monday is a big day.
Wish me luck that the readings on Monday show something that the engineers at Outlaw can help.

Scott e-mailed me the information I would need to take a reading with an analog Volt meter. I sent him the results today.

I had a reading of 0.5-1.

Sorry guys but I have no idea what this means or better yet how the issue is going to be resolved.
Hopefully Scott will touch base with me tomorrow.

What were you being asked to measure?

I was testing for DC current on AC line.

XM and to all involved with this post.
Thank you all.
Scott contacted me via e-mail and said that my readings of 0.5-1 were significant levels of DC on my AC line.
Scott said that Outlaw sells DC filters that will eliminate or reduce the level of DC hum.
Cost $249.00...I was not looking to spend that money right now b/c of saving for another processor, however this seems necessary.

I looked at Outlaw product menu and I only see two products from Surge X. One lists at $449.00 and the other at $289.00. I am not sure if Scott is referring to one of these units but I intend to contact him today.
I am a little confused since I have a Furman Elite.

I have decided that before I spend that money I will in the following week take a serious look at my wiring and I will probably strip my entire system and do a re-wiring of all components.

Again Thanks for your suggestions on a not so easy problem.

Here is another shot in the dark. Try swapping the breaker which feeds your circuit with either a new on or a similar rated one already in use. The device inside the breaker that senses an overload could be causing some noise on the AC line. New breaker is $6 vice big bucks.

Good thought XM.
I'll give it a try.

Another shot in the dark.... Borrow or buy a receptacle checker and check every outlet in your home for correct polarity. If even one is reversed it could be sending voltage to the neutral side of your house wiring and may be an easy issue to fix once found. The equipment plugged in is expecting 120 vac on the hot side of the receptacle (the smaller slot)and ground on the larger slot. If one of the wires in the house is reversed then you could be generating a voltage on the neutral lead. Essentially you could find it by reading the voltage witha multimeter, between the larger slot and the ground. There should be no voltage. If there is voltage one of the hot wires is connected to the neutral somewhere in your house. If any recent wiring was done I would start there.

I don't see anything in the Furman docs that indicate that they have a DC block. Surge protecction and AC filtering are called out, but those are usually implemented in such a way that DC will pass. If it's in there I didn't see it advertised.

Depending on which model you have, Furman has LIFT (linear filtering technology) which sounds like it would remove the noise from the AC line. An inline transformer would also remove any DC signal.

The Furman product for "DC hum elimination" -- http://www.furmansound.com/pdf/manuals/IT-1210_manual.pdf#search=%22isolation%20transformer%22

I have had good experience with the products from TrippLite as well, though the styling is definately "hide it behind something else".... http://www.amazon.com/Tripp-Lite-IS1000-Isolation-Transformer/dp/B00006HPFI/ref=pd_cp_e_3


Mixed reviews on this puppy -- low bid is definetely worth a try. It has worked for others...
http://www.ebay.com/itm/ps-audio-upc-200...=item20cef42e66

http://ubb.outlawaudio.com/ubbthreads/ub...ite_id=1#import

Thanks
I will have to check out the Furman Elite. I am looking into products that will eliminate the hum at a not so costly measure.

Thanks renov8r