[Speedskater]

In a normal AC power system the lone ground rod connection to Planet Earth shouldn't have anything to do with hum. But adding another connection to P.E. from the internet, cable TV, an audiophile ground rod or a mis-wired balanced power system can.
Normal trouble shooting is to simplify. Powering everything from AC outlet, plug in one component at a time, with internet & cable TV last. If everything works, use the same procedure with both circuits.

[Speedskater]

With two 120V circuits wired on the same leg or pole (aka phase), measuring the Hot of one to the Hot of the should only be a very few volts. Measuring the Hot of one to the Neutral or Safety Ground of the other should be about 120V.
The lone ground rod has nothing to do with day-to-day AC power quality (or hum) it's there for safety reasons. But if part of the hi-fi system is connected to one ground rod and part to another ground rod there probably will be hum.

Correctly wired balanced interconnect systems shouldn't hum. But some audiophile components aren't correctly wired.

[DaveC113]

I checked the dedicated lines and I am getting 119 V on one line and 120V on another
Could this be a clue?
Previously, it was 119V on both.

This was checked from hot to neutral and from hot to ground to see if there was a difference. There was not. Shouldn't this mean the grounding is OK?

However, I went outside and found the ground rod. It's a piece of rusty rebar very corroded. Unknown length. The copper wire is still good though.
The old telephone system is grounded about 40 feet away around the back of the house to a piece of galvanized pipe that runs into part of the concrete poured patio area.
The telephone system is Not used but I cleaned up that ground and there was no change.

I purchased two new copper plated 8 ft ground rods and will install those sometime this week.

I still am very concerned about the Loud buzz noise that the speakers make when the amps turn off. It's the same in both channels. It's quite loud- kind of like a large bumble bee / large winged grasshopper but metallic, slower in cadence and has static noise. It rises, falls and diminishes in about 2 seconds. These have NEVER made this noise before. I unplugged all devices from the 2nd dedicated outlet and the noise is still there.

Did you try plugging your entire system into ONE line? Did you measure potential difference in component grounds when you're using both lines? If there's a potential difference then there's your hum... it happens all the time when setting up equipment for live shows, it's very common for there to be potential differences between grounds of different circuits.

IMO, most people hurt themselves by running multiple lines for a system, it's fairly rare that more than one line is actually required or will make any sort of audible improvement, but the SCIN induced by the multi-line setup raises the noise floor, obscures fine detail, etc...

And, SS is right about the ground rod, you want to make sure you have a good connection for safety's sake but planes, trains and automobiles somehow have noise-free audio systems without using ground rods...

[jmdesignz2]

Thanks for all the suggestions -I floated the ground on one of the amps and the higher frequency hum went away in THAT channel. As did the nasty rattly buzz fade out when shutting off the amp.

I should Note that having ONLY the amps running off their own dedicated outlet the Hum and Buzz still is there. I would assume this is the same as having all devices operate off the same circuit.

However, this is dangerous for a powerful amp to be used with it's ground floated.

In addition, nothing was changed in the house or system prior to this New nasty hum during operation / buzz on shut off.

The only thing that changed was that it rained pretty hard for a few days.

Could there be a short somewhere in the house? Why did the voltage change from the dedicated outlets? Previously they were both 119V. Now one is 119 and the other is 120V
strange

I am close to calling an electrician for help...

[Folsom]

I checked the dedicated lines and I am getting 119 V on one line and 120V on another
Could this be a clue?
Previously, it was 119V on both.

This was checked from hot to neutral and from hot to ground to see if there was a difference. There was not. Shouldn't this mean the grounding is OK?

However, I went outside and found the ground rod. It's a piece of rusty rebar very corroded. Unknown length. The copper wire is still good though.
The old telephone system is grounded about 40 feet away around the back of the house to a piece of galvanized pipe that runs into part of the concrete poured patio area.
The telephone system is Not used but I cleaned up that ground and there was no change.

I purchased two new copper plated 8 ft ground rods and will install those sometime this week.

I still am very concerned about the Loud buzz noise that the speakers make when the amps turn off. It's the same in both channels. It's quite loud- kind of like a large bumble bee / large winged grasshopper but metallic, slower in cadence and has static noise. It rises, falls and diminishes in about 2 seconds. These have NEVER made this noise before. I unplugged all devices from the 2nd dedicated outlet and the noise is still there.

Actually, I should have specified that I meant signal lines, not power.

[Bob2]

"I floated the ground on one of the amps and the higher frequency hum went away in THAT channel"
Ah.. a clue..

[jmdesignz2]

"I floated the ground on one of the amps and the higher frequency hum went away in THAT channel"
Ah.. a clue..

Floating the ground in the Left channel also makes the buzz go away in the Left channel. Basically, if the ground is floated in X channel the hum goes away in X channel.


So definitely the noise is coming through the ground leg.

This means that somewhere there is a short to the ground or some other interference going on

[jmdesignz2]

the extra noise when the amp capacitors are discharging is another clue

Could that be some sort of feedback?

Not sure what this indicates though...

[Bob2]

"the extra noise when the amp capacitors are discharging is another clue
Could that be some sort of feedback?"

I wish I could answer that. Many here are far more knowledgeable than I.
I can only speak to the experiences I have had building my amps. Floating the ground took care of the issue for me.
I do hope you can clear this matter up quickly. Best of luck!

[jea48]

Reading page 1 of this thread I am inclined to agree with Scotty's response, Reply #11.
From the sound you describe you are hearing it sounds more like the probable problem, as Scotty described in his post, than a ground loop hum. Usually a ground loop hum is 60Hz, not a high pitch squealing sound.



When you checked the voltage at one dedicated circuit and it measured 120V and the voltage on the other dedicated circuit measured 119V the measurements are meaningless without knowing how the measurements were taken. Were the measurements taken with a load connected to the circuits? If so were the loads identical?
If the voltage measurements were taken without any load connected to each dedicated circuit then I would like to know if both of the circuits are fed from the same Line, leg, from the electrical panel. Simple test is to insert one meter test probe into the hot contact of a receptacle connected to one of the circuits and the other test probe into the hot contact of a receptacle of the other circuit. If both circuits are fed from the same Line, leg, you will measure zero volts nominal. If you measure 240V nominal then one circuit is fed from Line 1 and the other is fed from Line 2.
Check to make sure what you have. IF your problem is indeed related to the recent rain fall I would be curious to know it the electrical service feeding your house is fed overhead. Rain can cause problems on the outside connection,connectors, if the connection/s are poor. 

As for your cheater plug test, lifting the ground from only one mono amp.
 Problem with your test, the signal ground of each mono amp are tied together when the amps are connected to the DAC. I would suggest you try one amp at a time connected to the DAC without using a cheater and repeat your test shutting off the connected amp. Then repeat the test with only the other amp connected

Earth grounding connection.

Are you sure you only have one earth connection for the electrical service? The outside ground rod?
How about the domestic water pipe that enters your house? If it is metallic, steel or copper, it should also be connected to the electrical service. The connection should be made ahead of the water meter and within 5ft where the water pipe enters the house. There should also be a wire jumper around the water meter.

All earth connections must connect to the electrical service entrance neutral conductor. That includes CATV, SAT, and phone, must connect to the electrical service main grounding system. Where other systems entering the house are connected to earth using separate ground rods those ground rods must connect to the main electrical service grounding system by a minimum #6 copper bonding ground wire.

   

[DaveC113]

I would assume this is the same as having all devices operate off the same circuit.

No, I said ALL components running off ONE circuit. IMO, it's likely a potential difference in the grounds between your amps and preamps, which are powered by different circuits and have grounds that are connected via IC cables AND power cables so there can be SCIN and/or ground loops. For most systems running multiple lines only causes problems, but I'm tired of repeating myself...  The fact lifting ground on one amp eliminated the problem point to the possibility that I've been right about your issue all along... you might want to re-read my previous posts.

[jmdesignz2]

No, I said ALL components running off ONE circuit. IMO, it's likely a potential difference in the grounds between your amps and preamps, which are powered by different circuits and have grounds that are connected via IC cables AND power cables so there can be SCIN and/or ground loops. For most systems running multiple lines only causes problems, but I'm tired of repeating myself...  The fact lifting ground on one amp eliminated the problem point to the possibility that I've been right about your issue all along... you might want to re-read my previous posts.

I have been re-reading the posts. Will pursue leads (no pun intended)

However, I am stumped as to why this cropped up when no changes were made to any of my electrical systems / connections equipment etc. This new hum just appeared and frustratingly since I had just resolved a hum and the system had been dead quiet until these recent hard rains.

[G Georgopoulos]

the extra noise when the amp capacitors are discharging is another clue

Could that be some sort of feedback?

Not sure what this indicates though...

extra noise/hum when caps discharge indicates the caps need replacing - or in the case of a mod there need to be more capacitance...cheers

[ketcham]

Another consideration.  Dimmer switches.   See if they all are completely off in the house.  Does the noise stop or change intensity.   Yes, they can cause issues in your alternating current even when said dimmers are not on your dedicated lines.  Plus the second component is radio frequency emission and your particular RCA cables.  Dimmers also emit RF and create these symptoms.  I find led compatible dimmers particularly noisy. 

[jmdesignz2]

extra noise/hum when caps discharge indicates the caps need replacing - or in the case of a mod there need to be more capacitance...cheers

Both channels at the same time? But no noise when grounding is floated  at the outlet

[jmdesignz2]

Another consideration.  Dimmer switches.   See if they all are completely off in the house.  Does the noise stop or change intensity.   Yes, they can cause issues in your alternating current even when said dimmers are not on your dedicated lines.  Plus the second component is radio frequency emission and your particular RCA cables.  Dimmers also emit RF and create these symptoms.  I find led compatible dimmers particularly noisy.

House has zero dimmer switches

[DaveC113]

I have been re-reading the posts. Will pursue leads (no pun intended)

However, I am stumped as to why this cropped up when no changes were made to any of my electrical systems / connections equipment etc. This new hum just appeared and frustratingly since I had just resolved a hum and the system had been dead quiet until these recent hard rains.

Yeah, it can be hard to understand and hard to fix sometimes. I've definitely had some odd things like this happen over the years... good luck! 

[Bob2]

I know you wrote about your ground rod. Have you replaced that yet? Have more than one?
Not sure about other areas but I know where I live, more than one ground rod is not recommended.
Increased amount of rain indicates to me that ground contact would have me taking care of that first..
Perhaps this has been addressed. Too many lengthy comments  to sift through.
All the best correcting this issue..
Bob2

[jea48]

Bob2 said:

Not sure about other areas but I know where I live, more than one ground rod is not recommended.

Your whole yard could be full of ground rods as long as they all connect together or connect to one point. The electrical service entrance neutral conductor.

Here is an old Link where 2011 NEC is used. There has been a few changes since then but it pretty much is the same for 2014 NEC.

http://lightning.org/wp-content/uploads/2014/12/Bonding-2013-ULPA-LPI-rev1.pdf

Look at the picture shown in the Link

All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8 shall be installed and used.

As always the AHJ (Authority Having Jurisdiction) has the final say.
.

[Bob2]

"As always the AHJ (Authority Having Jurisdiction) has the final say."
Actually my electrician had the final say.
Being an audiophile he has investigated this.
He, as I stated and you paid no attention to, did not recommend it. His comment to me that more than one was not needed.
There was no mention of regulations or laws regarding this in my post.
Based on his 38 years in the trade, both residential and industrial and a personal friend, I'll go with his recommendation over yours anytime.