Mystery Lots of Rain = New Hum in System

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jea48

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Re: Mystery Lots of Rain = New Hum in System
« Reply #40 on: 16 Jan 2017, 07:48 pm »
"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.

I don't know your friend and I have no way of knowing what he actually said to you or what you may have understood he said, as it pertains to the minimum required standards for the grounding electrode system for an electrical service in your State, and or city, where you live. Though I would imagine he was referring to isolated ground rods that were not bonded to the grounding electrode system of the electrical service. 

IF indeed your friend is a licensed electrician then he is required to follow the National Electrical Code and or as well as the AHJ, minimum electrical code safety standards. He does not get the option to pick and choose the minimum standards, as I am sure he will tell you.

Not sure why you took my post so personal. It was meant as an educational post. My intent was not meant to demean or attack you personally. I apologize if you were offended in any way.

Maybe you could ask your friend to read what I have posted in this thread and find out for sure if he disagrees with what I have said.

I an sure he is quite familiar with NEC 2014  Article 250. Especially with over 38 years of practical experience working in the trade on commercial and industrial buildings/facilities.

Best regards.

EDIT:

 250.4 (A)(1)

    Electrical System Grounding.
    Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by, lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.


IEEE

    The IEEE Green Book also states that ‘field experience and theoretical studies have shown that arcing, restriking, or vibrating ground faults on ungrounded systems can, under certain conditions, produce surge voltages as high as six times normal. Neutral grounding is effective in reducing transient voltage buildup from such intermittent ground faults by reducing neutral displacement from ground potential and reducing destructive effectiveness of any high-frequency voltage oscillations following each arc initiation or restrike,’



 

G Georgopoulos

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Re: Mystery Lots of Rain = New Hum in System
« Reply #41 on: 16 Jan 2017, 11:30 pm »
Both channels at the same time? But no noise when grounding is floated  at the outlet

now you have a ground loop problem,which has nothing to do with ps caps

cheers  :green:

DaveC113

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Re: Mystery Lots of Rain = New Hum in System
« Reply #42 on: 17 Jan 2017, 03:47 pm »
now you have a ground loop problem,which has nothing to do with ps caps

cheers  :green:

Historically, after over 1000 GG posts, this may be the first time I agree with him. So I'm probably wrong...  :icon_twisted:

jea48

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Re: Mystery Lots of Rain = New Hum in System
« Reply #43 on: 17 Jan 2017, 04:00 pm »
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.

jmdesignz2,

What is the digital source you are using that feeds the digital input of the DAC?

A phone line modem?

A CATV modem?

Please explain.

I am trying to understand the makeup of your audio system.
Is this basically what you have?

 Some type of outside digital source entering your house by a phone line or coax cable >> to >> a Modem >> to >> a Computer >> to >> a DAC >> to >> two mono amplifiers.

Is that correct?
If that is correct disconnect the digital input cable from the DAC and then check for the high frequency squealing buzz/hum you are hearing.

Post back your findings.

EDIT:

One other question. Does the modem and or DAC have a three wire grounding type plug?


jea48

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Re: Mystery Lots of Rain = New Hum in System
« Reply #44 on: 17 Jan 2017, 04:10 pm »
Historically, after over 1000 GG posts, this may be the first time I agree with him. So I'm probably wrong...  :icon_twisted:

DaveC113,

This is not your typical garden variety ground loop hum though, would you agree?

jmdesignz2 said:
Quote
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.

I would think the ground loop hum would be present and consent while the amps were powered on as well. Would you agree? 

DaveC113

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Re: Mystery Lots of Rain = New Hum in System
« Reply #45 on: 17 Jan 2017, 04:23 pm »
DaveC113,

This is not your typical garden variety ground loop hum though, would you agree?

jmdesignz2 said:
I would think the ground loop hum would be present and consent while the amps were powered on as well. Would you agree?

I haven't been given enough info to say with any certainty. The fact that the buzz went away on the channel when the amp's ground was lifted, and that there's the same exact noise on both amps means it's probably not PS caps going out. Yes, if there's a ground loop hum it should be audible at all times, which I think is the case...

My initial thoughts are he's running his system on two separate circuits, this is often an issue... if a CATV/etc. ground is also involved here then that's another potential source of problems and even more likely to be a problem than running a system on 2 separate AC lines.

jea48

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Re: Mystery Lots of Rain = New Hum in System
« Reply #46 on: 17 Jan 2017, 05:11 pm »
I haven't been given enough info to say with any certainty. The fact that the buzz went away on the channel when the amp's ground was lifted, and that there's the same exact noise on both amps means it's probably not PS caps going out. Yes, if there's a ground loop hum it should be audible at all times, which I think is the case...

My initial thoughts are he's running his system on two separate circuits, this is often an issue... if a CATV/etc. ground is also involved here then that's another potential source of problems and even more likely to be a problem than running a system on 2 separate AC lines.

I reread the OP's posts this morning and maybe I missed it, but he really doesn't say the hum/buzz is present all the time while the amps are powered on. From what I understand his concern is when he turns off the power to the amps.

Quote
My initial thoughts are he's running his system on two separate circuits, this is often an issue... if a CATV/etc. ground is also involved here then that's another potential source of problems and even more likely to be a problem than running a system on 2 separate AC lines.

I posted asking some questions for the OP to answer above. Hopefully he will respond.
He said in an earlier post the phone line lightning grounding arrestor ground wire was connected to a dedicated earth ground rod. IF..., the ground rod is not bonded, connected, to the main grounding Electrode system of the electrical service then there is a very high probability a difference of potential, voltage, will exist between the two earth connections. IF..., the OP is using a DSL phone line modem that connects to his audio system in any way that could be the source of his problem.

As for the two dedicated 120V 20 amp branch circuits that feed the two amps if the dedicated circuits were installed using the proper accepted branch circuit wire and wiring methods that should/would not be a problem. IF......

He could try, maybe he already has, plugging both amps into only one of the dedicated circuits. In fact plug all the associated equipment that is connected together with wire ICs or patch cables where the signal ultimately reaches the two amps.

It also should be mentioned, as I mentioned in an earlier post, the signal grounds and most likely the power supply B- rails of the two amps are tied together when they are connected to the DAC's analog output jacks. Would you agree?
 
 

DaveC113

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Re: Mystery Lots of Rain = New Hum in System
« Reply #47 on: 17 Jan 2017, 05:56 pm »
I reread the OP's posts this morning and maybe I missed it, but he really doesn't say the hum/buzz is present all the time while the amps are powered on. From what I understand his concern is when he turns off the power to the amps.

I posted asking some questions for the OP to answer above. Hopefully he will respond.
He said in an earlier post the phone line lightning grounding arrestor ground wire was connected to a dedicated earth ground rod. IF..., the ground rod is not bonded, connected, to the main grounding Electrode system of the electrical service then there is a very high probability a difference of potential, voltage, will exist between the two earth connections. IF..., the OP is using a DSL phone line modem that connects to his audio system in any way that could be the source of his problem.

As for the two dedicated 120V 20 amp branch circuits that feed the two amps if the dedicated circuits were installed using the proper accepted branch circuit wire and wiring methods that should/would not be a problem. IF......

He could try, maybe he already has, plugging both amps into only one of the dedicated circuits. In fact plug all the associated equipment that is connected together with wire ICs or patch cables where the signal ultimately reaches the two amps.

It also should be mentioned, as I mentioned in an earlier post, the signal grounds and most likely the power supply B- rails of the two amps are tied together when they are connected to the DAC's analog output jacks. Would you agree?


Without opening up the gear and looking at how the grounding is done all we can do is speculate, and with XLR cables there are even more possibilities as pin1 may or may not be connected at both ends of the cable. Personally, I generally make some attempt to isolate the component and I don't connect the IEC inlet ground directly to anything. Isolation also may or may not be used from pin1 to chassis. There's just so many possibilities and incomplete standards, you just never really know...

What it seems to me, is the grounds of the preamp/DAC and amps are at different potentials... just a guess though :)