@ tomiiv30 As for DC on the AC mains. Nelson Pass
If you are experiencing mechanical hum from your
transformer, it is often caused by the presence of
DC on the line. Usually this comes from some appliance
using current asymmetrically, such as a lamp dimmer.
The hum comes usually from toroidal transformers, which
saturate easily with DC, and when they recover, they
draw an extra pulse of current, causing the noise.
You can put a pair of back-to-back electrolytics in series
with the AC power line to block this, and it works fine.
Makes sure the current rating of the electrolytics is
high enough, and the they are joined at a like polarity,
such as + to +. https://www.diyaudio.com/forums/solid-state/2080-dc-filter.html Re: Not trying to start a flame but.... "If your not comfortable with a meter get an electrician or tech that knows his way around test equipment. " If you read the comments in the AA archives, you would have seen the ones from real engineers (Jon Ricsh, John Curl, etc)who have measured this. They report that most hand held DVMs cannot measure this (John Curl tried three different Fluke models with mixed results). If you really want to try and measure the DC off-set on your AC line with a cheap hand-held DVM, try the following: Put a 100K resistor in series with a 100µF cap (this is called an integrator). This now goes in parallel with the AC line. Measure the DC voltage across the cap. Even a few tens of mV DC off-set can make a toroid buzz, especially low priced ones. The image here is a PA Audio DC blocker. Note the two series connected bridges, this gives four forward diode drops vs the two of the Bryston circuit. Note also that the caps in parallel with the diodes are very small, just for RF suppression. The original LC Audio filter was similar to this PA Audio one as well, only they used three forward diode drops, and only small RF caps.
http://db.audioasylum.com/mhtml/m.html?forum=tweaks&n=140383&highlight=integrator+djk&r=...JMHO, if the mechanical buzzing on one of the transformers is caused by DC on the AC mains, then both transformers would be buzzing. . |
tomiiv30 OP11 posts01-02-2019 8:10pm
@stereo5
I just got an email from the salesman I bought it from and told me that he would talk to service dept. to see if they can check or have checked the one I returned. I would also be bringing this one to them as well and have them plug it in while I am there no matter how busy they are.
Check the serial numbers of the two units. My bet is they are close to one another. |
@ tomiiv30 Your profile list country as N/A. By chance do you live in the USA? I have McIntosh MC8207, the first unit I bought from an authorized dealer came with a loud buzzing coming from the left transformer, and was replaced with a new unit which came with even a louder buzzing. The buzzing can be heard from 8 feet away. Then I was told to have install new 20 amp outlet that has its own isolated grounding. That was done professionally by an electrician who installed two isolated 20 amp outlets, two 20 amp circuit breakers, two copper polls for grounding for each outlet, each outlet has its own neutral and power line. After all this done the buzzing sound was still there. Then I was told to have install new 20 amp outlet that has its own isolated grounding.
That was done professionally by an electrician who installed two isolated 20 amp outlets, two 20 amp circuit breakers, two copper polls for grounding for each outlet, each outlet has its own neutral and power line. After all this done the buzzing sound was still there. If you live in the USA the so called electrician is no electrician. Definitely not a qualified licensed electrician. No way in hell! two copper polls for grounding for each outlet, I assume you mean two earth driven ground rods. DANGEROUS and not electrical safety code compliant. Not NEC or any AHJ in the USA. IF the branch circuit wiring is Romex an isolated grounding type receptacle serves no purpose what so ever. Per NEC code the insulated equipment grounding conductor that connects to the isolated ground terminal on an IG receptacle shall terminate on the ground bar in the electrical panel the branch circuit is fed from. Exception: NEC allows the insulated IG equipment grounding conductor to pass through a sub panel and to be connected to the equipment ground bar in the main electrical service panel. NO isolated ground rods allowed for IG receptacles. |
From the MC8207 owner manual Power Supply Circuits
To compliment the design of the MC8207, there is a high current power supply for the five power amplifier channels. Refer to figure 21. The very large Power Transfomer, has toroidal windings on a toroidal core and can supply over 35 amps of continuous current. Refer to figure 22 (golf ball is for size comparsion). It is enclosed in the legendary McIntosh Potted Enclosures and weighs over 12kg. The super size main filter capacitors can store over 340 Joules of energy for the seven amplifier channels, necessary for the wide dynamic range that “Digital Audio” demands. The power amplifier draws high current from the AC power line. Therefore, it is important that they plug directly into the wall outlet.
See page 15 http://stereobarn.com/wp-content/uploads/mcintosh-mc8207-amplifier-owners-manual.pdfWhere’s the second transformer? Am I missing something? The very large Power Transfomer, has toroidal windings on a toroidal core and can supply over 35 amps of continuous current. 120V X 35 amps = 4200VA. Just a guess the transformer is rated at 5Kva. |
tomiiv30 OP14 posts01-03-2019 12:00am@jea48
With
my amp only one is buzzing, the left one, so lets say I do have dc on
my ac line why would only one buzz? IMHO I think that the one that buzz
is a bad one comparing to the right one which is a good one. It would be
the only explanation.
So what I did was, I turned off every switch
in the house except the on the amp is plugged in and yes the buzzing
sound got quieter but was still present. But having an expensive amp
that has much better transformer than a cheap amp this little
interference when all breakers are on should do nothing to it.
I bet
you that every house has the same problem when you have multiple things
running in a house such as ac units, furnaces, washers and dryers etc,
you can't tell me that there is going to be no interference at all, but
this expensive amps should take care of that problem. - I could be
wrong.
I agree,
McIntosh
should have incorporated a DC blocker circuit in the amplifier.
So what I did was, I turned off every switch
in the house except the on the amp is plugged in and yes the buzzing
sound got quieter but was still present. But having an expensive amp
that has much better transformer than a cheap amp this little
interference when all breakers are on should do nothing to it.
The DC on the AC mains could/can be coming from a neighbors house that is fed from the same power company's utility power transformer as yours. Just doing a quick Google search I found this manufacture of a DC blocker. You might give them a call and see if they can build you one to handle the power requirements of your amp. JMHO, the one shown is not big enough. Make sure you give them the AC power requirements info for the amp. https://avahifi.com/products/humdinger-dc-line-blocker |
|
tomiiv30 OP16 posts01-03-2019 12:48pm@jea48
In the manual it says "To compliment the design of the MC8207, there is a high current power supply for the five power amplifier channels". And this is a 7 channel amp so what about the other 2 channels. And why is there two boxes, what’s in them if there is only one transformer. I am trying to understand what is what. @ tomiiv30 The box on the left houses the power transformer. The box on the right houses the DC power supply. Rectifiers and electrolytic caps. Scroll down page to photo of amp. http://www.hifishock.org/gallery/electronics/mcintosh/power-amplifier/surround-sound/mc8207-1-mcinto... |
tomiiv30 OP17 posts01-04-2019 9:41pm
Also I have measured for DC offset in my AC line the the result was 0.9mV, which is not enough to cause the transformer to buzz How did you measure for it? The correct way.
Re: Not trying to start a flame but.... "If your not comfortable with a meter get an electrician or tech that knows his way around test equipment. " If you read the comments in the AA archives, you would have seen the ones from real engineers (Jon Ricsh, John Curl, etc)who have measured this. They report that most hand held DVMs cannot measure this (John Curl tried three different Fluke models with mixed results). If you really want to try and measure the DC off-set on your AC line with a cheap hand-held DVM, try the following: Put a 100K resistor in series with a 100µF cap (this is called an integrator). This now goes in parallel with the AC line. Measure the DC voltage across the cap. Even a few tens of mV DC off-set can make a toroid buzz, especially low priced ones.
http://db.audioasylum.com/mhtml/m.html?forum=tweaks&n=140383&highlight=integrator+djk&r=... . Here is another Link for measuring DC on AC mains. http://sound.whsites.net/articles/xfmr-dc.htm#dc1 However, if you must (and PLEASE take extreme care), you need a 100k resistor and a 10µF non-polarised capacitor, wired in series. Connect this circuit across the mains (power off!), and connect a DC voltmeter across the capacitor. This attenuates the AC enough to prevent the front-end of the meter from being overloaded, and the DC voltage is easy to measure. Expect to see the DC vary around the zero voltage, with a normal variation of ±25mV or so (typical - residential areas). The alternative method is to measure the DC across the diode/capacitor network in the circuit of Figure 3. Do not connect or disconnect the meter with the circuit live, and use alligator clip leads to make the connections. . |
tomiiv30 OP21 posts01-05-2019 12:47pm
And this is what I get from the dealer:
"Ron from McIntosh says he might hear of this buzzing issue 5 times a year. It is an amp that is 14,000 watts so it is sensitive to DC being present in the lines. He said it has to either be the electrical coming from the pole or something within your house that is introducing DC in the AC of the lines ie. Faulty/poorly designed dimmer switch or something similar. So it is certainly not the amp or us, it is something going on at his specific home. It could be something as little as 1 volt of DC that can cause this issue."
Does this look like the McIntosh is siding with the dealer and not me, is it my f’ing problem that I spend over $20K on Mac product to be told that I am in the wrong. It is an amp that is 14,000 watts so it is sensitive to DC being present in the lines. I think you meant 1400 watts. He said it has to either be the electrical coming from the pole or something within your house that is introducing DC in the AC of the lines ie. Faulty/poorly designed dimmer switch or something similar. So it is certainly not the amp or us, it is something going on at his specific home. It could be something as little as 1 volt of DC that can cause this issue." No,.... there’s nothing wrong with the AC power in your home. You measured for DC offset on the AC mains using your DMM and measured 0.9mv. You measured for DC offset exactly as McIntosh told you to do it. Exactly! tomiiv30 OP21 posts01-05-2019 10:40am
@jea48 When I called Chuck at McIntosh and told him my problem he said and these were his words" Get a multi meter and stick probes one into the neutral the other into the phase and measure for DC mV, and that’s what I did. I am not going to do anything more than what they suggested.
Chuck is the man, he should know. He is McIntosh’s expert on the subject. You followed his instructions to the letter. Can’t get any simpler than that. There is nothing wrong with the AC power in your home. The power transformer in the amp is defective. Period! . |
erik_squires4,643 posts01-06-2019 11:54am
Agreed.
If you measure that little, you need to take the amp back and prove it there.
Best,
E erik, keep this just between the two of us. Chuck is just plain ignorant when it comes to how to measure for DC offset on the AC mains. Jim |
Food for thought. Quote from an Audio Circle audio forum thread about DC offset on the AC mains.
HAL
- Industry Contributor
-
- Posts: 4101
-
-
Re: DC offset on AC line
« Reply #8 on: 30 Nov 2007, 03:51 am »
If you have access to a Fluke
43B power line analyzer, you can check the harmonic distortion on the
AC line. Had a similar problem with lots of audio gear in the house.
Turned out the the AC line harmonic distortion was running about 6%.
The
local power company did some investigation. Found out the meter base
contacts had corrosion. After clean up, the AC line distortion runs
about 2%. No more power transformer hum.
https://www.audiocircle.com/index.php?topic=47973.0. |
https://www.diyaudio.com/forums/solid-state/2080-dc-filter-6.html#post331815
22nd February 2004, 08:09 PM
#57
Eva
diyAudio Member
Join Date: Oct 2003
Location: Near the sea
I've done some measurements that show what's really hapening when you connect a transformer to mains
Using a lowpass filter [100k + 47uF] I have measured about 50mV average over time of DC on my mains supply
I also have an old electric heater that in half-power mode uses a diode
in series with the heat element to pass only half of the mains waveform.
When I plug this heater in half-power mode I get an additional 1V of
offset on mains supply
To test the need and the efficiency of DC filtering, I've done some
measuremens of the current through the primary of a 750VA toroidal
transformer
This oscillogram shows what happens when I connect the transformer to mains and let it deal with the 50mV DC offset
An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.
Blue trace is mains waveform at 100V/div [230V AC], it looks more like a
clipped triangle wave instead a sine wave due to the line inductance
limiting the slew rate and all the rectifiying applications consuming
all the current only during the peaks [30% of total time]
Red trace is the current through the primary at 200mA/div. Transformer
saturation towards the negative side is evident, reaching 350mA peak of
leakage current. The transformer buzzs slightly due to the saturation
The noise present in the current waveform is common mode and was
suppressed in further measurements adding a common mode filter between
mains and measurement point
The second oscillogram shows what happens when I plug the electric heater in half-power mode
An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.
Red trace this time is in 2A/div so the leakage peak current exceeds 6A.
The transformer is heavily saturated towards the upper side and buzzs
loudly.
The third oscillogram shows what happened when I placed a DC filter
consisting of two 1000uF 16V and some diodes in series with the primary
An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.
This time, red trace is 20mA/div and shows the small leakage current due
to both the magnetizing inductance and the parasitistic capacitance
between adjacent turns. The transformer is no longer saturated and
performs silently
the fourth oscillogram shows the induced voltage in a loop of wire of
10cm diameter placed vertically, paralell and 1cm away from the
transformer [placed horizontally] obtained when the transformer was
saturating with more than 6A peak [with the electric heater plugged]
An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.
The red trace is 2mV div and shows the induced voltage in the loop of wire
That measurement demonstrates that when a 50-60Hz transformer is
saturating, it produces electro-magnetic-interferences that induce noise
voltages on everything in the nearhood
Actually, I think that +-5mV of low frequencies induced in a loop of
wire of 10cm diameter near the transformer is a serious thing since this
EMI is at audio frequencies, it's not RF so it's 100% audible and it
may be happening in all your transformers
In the other hand, all the tests were performed with open secondaries
but if we add load so that primary current has peaks of 6A, then the EMI
radiated would be the same or higher
With load, the EMI is produced due to flux in the leakage inductance,
resonances due to parasitistic inter-turn capacitance, RF ringing due to
diode turn-off characteristics and the fact that the peak current
through the transformer is 3 times or more the average DC current after
rectification
In conclusion : Rectifiying the output of 50-60Hz transformers produces
EMI as any SMPS does and this phenomena gets aggravated when the
transformer is saturating due to direct connection to mains without a DC
filter
50-60Hz transformers are nothing but big, bulky and crappy antennas
https://www.diyaudio.com/forums/solid-state/2080-dc-filter-6.html#post331815.
22nd May 2004, 05:20 PM
#71
Eva
diyAudio Member
Join Date: Oct 2003
Location: Near the sea
Bricolo :
DC levels on mains cannot be measured by directly connecting the
multimeter to the line. You have to place a low-pass filter between the
line and the DMM. I use a first order filter made of a 100K 1W resistor
and a 22uF non-polar capacitor for that purpose
Non-gapped transformers must be operated on 'pure AC'. Even 50mV of DC may be enough to see signs of saturation on toroids
. |
gdnrbob2,190 posts01-07-2019 1:21pm
@jea48 ,
Would you recommend getting a DC blocker for every system?
I know not all lines have DC, but just as a precaution?
Bob No, I wouldn’t. There is not any need for a blocker unless you have DC offset on the AC mains. If you have a piece of equipment with a torid transformer that is buzzing loudly then it may be being caused by DC on the mains. The best way to find out is to measure for it. Measure for it the correct way. I am surprised there is not someone building a low-pass filter device to use on the AC mains to measure for DC on the mains using a regular DMM. For a DIY project it would be pretty simple to make one. All you need is, 1 - male plug (to plug into the wall outlet) 1 - 100K 1 watt resistor 1 - 22uF non-polar capacitor 2 - alligator clips for the probes of the DMM Maybe a short piece of 2 wire zip cord Soldering Iron Solder You could even install the resistor and cap in a small PVC plastic box with cover. Connect a short 2 wire power cord and male plug. Install a couple of recessed insulated female jacks for inserting of the probes of a DMM. Jim . |
@ tomiiv30 OP and @ gdnrbob I ordered the resistor and capacitor over the internet yesterday to build the simple low-pass filter. Hopefully I will have them in about a week. 100K 1 watt resistor https://www.ebay.com/itm/5-pack-1-watt-5-carbon-film-resistors-100k-ohm/160460118738?hash=item255c2b...22uf non polarized capacitor. https://www.amazon.com/22mfd-Non-Polarized-Grade-Mylar-Capacitor/dp/B00B4DVXJE Eva (DIY Forum member) didn’t give the voltage rating for the 22uf non polarized capacitor so to be on the safe side I ordered 250V. I’ll post back with the testing results on how it works. Here is a link of a wiring diagram that shows the wiring, configuration, of a low-pass filter. (Disregard the white paper for the use in the paper). It’s the best I could find for a wiring diagram of the simple circuit. https://www.electronics-tutorials.ws/filter/filter_2.htmlYou need to redraw the simple circuit and add some wordage. ** ELIMINATE THE EARTH GROUND CONNECTION AS SHOWN ON THE BOTTOM LINE OF THE DRAWING. (This line will be the AC neutral.) Note on the left side of the drawing the two Vin AC (sine wave) line inputs. You will connect these to the 120Vac male plug. I would suggest the top line (resistor) connect to the Hot blade screw terminal of the plug. The bottom Line (other end of the capacitor) to the neutral blade screw terminal of the 120Vac plug. The right side of the drawing where it says (Vout) is where the DMM probes connect to. Edit: Another wiring diagram showing the Low-Pass Filter. In the last post by atmasphere in the link he provided there is a post with this link showing an Intergator Low-Pass filter. http://www.animations.physics.unsw.edu.au//jw/RCfilters.html#lowLow-Pass Filter scroll down the page to, "Integrator" . Note the diagram is the same as the first diagram for a Low-Pass filter. You don’t need an electrician to build, assemble, this low-pass filter to measure for DC offset on the AC mains. All you need to find is an electronic service tech. Or anyone with any experience in wiring a simple resistor capacitor circuit together. Jim . |
Al, (almarg)
Thanks! 10 to 15 seconds..... I would have missed that for sure.
What do you think about using a 22uF value for the capacitor? I chose the 22uF cap because that is what Eva (DIY member) said to use in her post.
Elliott Sound Products recommends using a 100K ohm resistor in series with a 10µF non-polarized capacitor.
What are your thoughts on the value of the capacitor used?
Jim
|
|
@ tomiiv30 OPI decided to deleted my previous post because I didn’t think it was right for me to instruct/dictate how the electrician, you hired, should go about trouble shooting for possible problems on the electrical service and or wiring of your home. I did save the first part of my post about the two ground rods that were installed for the equipment grounding of the two new dedicated circuits. I would appreciate it though if you would note and post back what the Line 1, leg, to Line 2, leg, voltages are as well as Line 1 to neutral and Line 2 to neutral voltages are at the electrical service panel. To high of an over voltage above the voltage rating of the torid transformer in the amp could also add to the cause for the transformer to buzz louder than it normally would. // @ tomiiv30 OP Make sure you ask the electrician exactly what he did with the equipment grounding conductors for the new dedicated branch circuits he installed. TAKE NOTES! A picture is worth a 1000 words. Have him physically show you exactly what he did. It is possible the electrician wired the new ground rods per NEC 250.54 ...... I’ll give the guy the benefit of the doubt. If he did wire the 2 ground rods per NEC 250.54 "Auxiliary Grounding Electrodes", then the equipment grounding conductors for each IG receptacle are connected to the branch circuit wiring equipment grounding conductor and the equipment grounding conductor of the branch circuit is connected to the equipment ground bar in the electrical panel the branch circuits are fed from. Per NEC 250.54 a ground wire is installed from the ground rod and is connected to the branch circuit equipment grounding conductor. He can use any any size wire he wants to use from the ground rod to the branch circuit equipment grounding conductor. Hell, it can be 20 gauge. Does an Auxiliary Grounding Electrode really do anything to improve the sound of an audio system? It can act as an antenna and add noise. It also provides another path for a lightning high voltage transient to enter your home. Lightning loves aux grounding electrodes. Jim . |
Here are the DC offset measurements using a low pass filter. (DMM probes across capacitor leads)
I used a 1875 watt hair dryer to create the DC offset on the AC mains.
Test # 1
Dedicated Audio room.
Low pass filter plugged into dedicated audio outlet. 120V, 20 amp branch circuit. Branch circuit wire is #10-2 with ground Romex. Length of Romex from wall outlet box to electrical panel is approx 75ft.
Low pass filter plugged into wall duplex outlet. No other loads connected to the outlet.
AC mains voltage at outlet, no load, measures 122.3Vac (DMM, Fluke 87 True RMS)
**EDIT: (I just checked mains unloaded voltage again so I could check for the hair dryer loaded voltage drop. Unloaded mains voltage at the outlet now measured 121.5Vac. Loaded, hair dryer turned on, high heat, low blower, measured 119Vac).
DC offset voltage measured across the low pass filter cap measured 1.6 mVdc, avg reading. (Fluke set on Dc mV scale).
I also used a Radio Shack DMM. Meter set on DC volt auto scale. It also read 1.6 mV avg.
With the hair dryer plugged in, heat on high, blower on low. (This combo setting gave the highest DC measurements).
Fluke measured 0.734Vdc (meter set on auto DC volts. Dc mv meter setting is for 400mV max.)
Radio Shack measured 0.726Vdc.
0.734Vdc (734 mVdc) is more than enough to saturate the core of a moderately sized torid and cause it to buzz loudly. From what I have read 50mVdc will cause a torid to buzz.
Just for the heck of it I ran a few more tests.
Test #2
Low pass filter plugged into same audio dedicated wall outlet.
Hair dryer plugged into a wall convenience outlet in the same room. Branch circuit is separate 20 amp, #12 Romex, for several conv outlets in the room. Approx length of the romex from the wall outlet, the hair dryer is plugged into, to the electrical panel 80 + ft.
Hair dryer turned on. High heat, low blower.
Fluke measured 112.6 mVdc - 113.3 mVdc (Meter set first to DC auto, then moved to mV setting)
Radio shack measured pretty much the same, 112.3 mVdc - 113.6 mVdc.
Here is where, hopefully, Al (almarg) chimes in.
With the hair dryer plugged into the same outlet as the low pass filter the Fluke measured 734 mVdc. With the hair dryer plugged into a different outlet fed from a different branch circuit the Fluke measured 113.3 mVdc.
Just a guess on my part, two things are at play. Both involve the total combined length of the two Romex cable branch circuits, (Approx 75ft + 80ft). One is the inductance of the cable and the other the resistance of the cable. Inductive reactance? One other thought to consider is the utility power transformer. Just going from memory harmonics will travel back on the neutral conductor to the source. Some of the harmonics are dissipated by the secondary winding in the form of heat.
If Al is still following this thread I am sure he will have a better technical answer.
Test #3
Hair dryer plugged into wall outlet in dinning room. Wire is Romex, #12 , 20 amp circuit. Approx length? Just a guess 80ft or so. (Up, down, and all around).
Low pass filter, still plugged into the dedicated audio wall outlet circuit, audio room.
Hair dryer on, high heat, low blower.
Fluke measured 106.7 mVdc.
Radio shack 105.8 mVdc.
Voltage at wall outlet unloaded measured 122.3Vac. With the hair dryer turned on voltage dropped to 116.2Vac.
Test #4
Hair dryer plugged into an outlet directly below the electrical panel.Fluke measured 115.6 mVdc
Radio Shack measured 115.4 mVdc.
Note, here only the audio dedicated 20 amp branch circuit wiring length is at play. Approx 75ft, #10awg wire.
One other thing...... I will have to go back this afternoon, maybe tomorrow morning, and Check for the Line, Leg, (in the electrical panel) that each of the branch circuits are fed from. (For tests 2, 3, and 4). There in, Line 1 or Line 2. I believe that would have some relevance. There’s a 50/50 chance, LOL, some are on the same Line as the audio room dedicated audio outlet circuit that the low pass filter was plugged into for all the tests.
Jim
.
|
jea482,863 posts01-15-2019 12:14pm
One other thing...... I will have to go back this afternoon, maybe tomorrow morning, and Check for the Line, Leg, (in the electrical panel) that each of the branch circuits are fed from. (For tests 2, 3, and 4). There in, Line 1 or Line 2. I believe that would have some relevance. There’s a 50/50 chance, LOL, some are on the same Line as the audio room dedicated audio outlet circuit that the low pass filter was plugged into for all the tests. They are all connected to breakers that are on the same Line. Line 1, leg. What are the odds? |
almarg8,581 posts01-15-2019 6:12pmIf Al is still following this thread I am sure he will have a better technical answer.
Not necessarily, Jim :-)
Your finding that having the hairdryer plugged into the outlet where the measurement was taken resulted in a DC offset of around 730 mv, while measuring at the same outlet but with the hairdryer plugged into various other circuit branches on the same leg resulted in around 115 mv, is indeed a bit of a headscratcher. Al, Ah, that’s nothing.... In another room there are also several 120V convenience wall outlets that are fed with a 20 amp separate circuit. Wire is #12-2 with ground Romex. Home run feed to first outlet, closet to electrical panel. Branch circuit Romex is run around the perimeter of the room to outlet boxes in an in and out configuration. Up and down, and all around. The length of the Romex from the first outlet to the elecrical panel is approx 45ft. The length of the Romex from the first outlet to the farthest, last, outlet in the room is approx 50ft. Approx 90ft total from the last outlet to the electrical panel. The test. I first plugged the hair dryer into the farthest duplex receptacle outlet. (High heat, low blower speed). Mains voltage unloaded, 120.8Vac. Hair dryer on, loaded, 115.8Vac. 5Vac VD. Plugged in the low pass filter in the same duplex outlet. Fluke measured 1.577Vdc . . ??? Higher than my previous post test of 0.734Vdc. What are the differences between the two branch circuits? Length of the branch circuit wire and the AWG wire gauge size. (0.734Vdc 75ft, 10-2. Mains loaded VD approx 2.5Vac) (1.577Vdc 90ft 12-2. Mains loaded VD 5Vac) I then plugged the Low pass filter into the first outlet. (Outlet closest to electrical panel. First outlet on home run feed.) Hair dryer left in farthest outlet. Fluke measured 0.578Vdc....... (Note DC offset is decreasing) I then plugged the low pass filter in the outlet just below the electrical panel. (Basically connecting the low pass filter to the electrical panel itself. The branch circuit source) Turned on the hair dryer. (High heat, low blower speed). Fluke measured 0.106Vdc (106.3mVdc) meter then set to mV. Note the harmonics, DC offset, decays the closer its gets to the source the electrical panel. Or does the source have anything to do with it? Final test. I plugged the hair dryer into the outlet directly below the electrical panel. Plugged the low pass filter into the first outlet closest to the electrical panel. Fluke measured 0.115Vdc, it then settled down to 0.114Vdc I then plugged the filter into the farthest outlet on the branch circuit. The Fluke measured 0.115Vdc. Same thing here it settled down to 0.114Vdc Both measurements were taken without a connected load on the branch circuit. For a load I plugged in a quartz construction work light in the farthest outlet. I think it’s a 500 watt but can’t remember for sure. I’d have to check it. I then measured the DC offset again. This time it measured 0.112Vdc. Jim . |
Thanks Al, (almarg) for the response. The additional difference of 1.577 - 1.41 = 0.167 VDC is probably accounted for by a combination of the resistances of the connections to the several intervening outlets in the room with the 1.577, and imprecision in the estimates of the run lengths. I don’t think so. All in and out wire connections along with the pigtail extended for the receptacle connection are twisted together and then made mechanically tight using Electrical Spring Connectors. The live wire steel spring inside the connector is designed to expand and contract with the copper conductors. Varying loads placed on the circuit conductors can cause the copper conductor to expand from heat and contract from cooling as load falls off. The connector’s wire spring always keeps the connection tight. Jim |
Yeah he came to the house checked everything again and he said not to
call him any more, he thinks that I am bulls^&#g with him, and
that's why I did not write anything about it.
What did you find out about how the electrician wired the two ground rods to the two new wall outlets for the two new dedicated branch circuits you had him install? |
@ tomiiv30 OP How about an update on your electrical. Did the electrician come out and check for possible electrical problems in your home? Possibly loose and or corroded wire connections in the electrical service panel? Have you spoken to any one yet from your utility power company? Jim |
@ nyev See page #17. It appears the power transformer is an EI type. EI type power transformers as a rule are not affected by DC offset on the AC mains https://www.manualslib.com/manual/1460643/Mcintosh-Mc462.html?page=17#manual
Question is why would you still want to buy a McIntosh product after hearing the way they have treated the OP? Ron ( McIntosh representative) said maybe 5 complaints a year about torid buzzing power transformers. You want to beat the number of complaints is actually higher than 5? How much would it have cost for McIntosh to incorporated a DC blocker in the MC8207 amp? I would be willing to bet the design engineer first designed the amp with a DC blocker. No doubt the design engineer new that a large torid power transformer would vibrate/buzz if there was DC offset on a customer’s AC mains. How much you think them pretty covers cost that cover the transformer and DC power supply inside the MC8207? Or them big pretty blue front meters? They sure look pretty though don’t they? Charlie Randall (top USA dog now) is already starting to make ARC equipment look like McIntosh. . |
tomiiv30 OP32 posts01-21-2019 2:05pm
It is one rod that he installed in the ground that is few feet away from the outside meter/box, the other rod was installed form the electrical company, it was already there, that’s why I thought he did 2.
One of the 20 amp outlet is grounded to the inside of the panel.
The other 20 amp outlet is grounded directly from the outlet to the outside rod with a clamp that is attached to the rod itself, I saw that with my own eyes. It is a straight wire that goes from the outlet to the outside and has nothing to do with the inside panel or anything else in the house. The other 20 amp outlet is grounded directly from the outlet to the outside rod with a clamp that is attached to the rod itself, I saw that with my own eyes. It is a straight wire that goes from the outlet to the outside and has nothing to do with the inside panel or anything else in the house. YOU are going to have to find out exactly what the guy did! Do you feel comfortable pulling the wall duplex outlet from the wall box for a look to see exactly what the guy did? IF yes. Turn off the breaker at the electrical panel that feeds the outlet. Plug a lamp into the outlet to make sure 100% the power is off. 100%! To verify the lamp is turned on and the bulb is good plug it into a live outlet. Lamp bulb should light. Pull off the outlet cover plate. Remove the two 6/32 screws that hold the outlet to the wall box. Pull the receptacle outlet straight out from the box far enough to look at the wires that are connected to the receptacle as well as those that enter the box. Is the box metal or plastic? As for the branch circuit wiring that enters the box, I believe you said in an earlier post it is Romex. You should see a black insulated wire (Hot), a white insulated wire (Neutral), and a bare copper wire, the safety equipment grounding conductor.WHERE IS THE BARE WIRE CONNECTED TO??? *****Examples: 1) ** IS THE BARE WIRE connected to the ground wire that comes in from the outside isolated ground rod along with a short wire, pigtail, that connects to the green equipment ground screw on the isolated grounding type receptacle outlet? IF the box is metal the box must also be bonded, connected, to the ground wires connection with another pigtail. All connections should be under one wire connector, example a wire nut. IF this is what you have then the guy wired the grounding per NEC Code as an Auxiliary Grounding Electrode. Lightning loves Auxiliary Grounding Electrodes! NOT NEC compliant! 2) ** IF a metal wall box was used the Romex cable bare copper safety equipment grounding conductor is bonded, connected, to the metal box ONLY. Period.... IF the box is plastic the Romex Cable bare equipment ground wire is not connected to anything. It is just pushed back inside the box. The ground wire that enters the wall box from the outside isolated ground rod connects to the green color ground screw on the isolated grounding type receptacle ONLY. Period.... If this is the way the guy wired the grounding it is dangerous and could cause an electrical shock hazard or worse possible electrocution in the event of a hot to chassis ground fault event. Also note you do not have a low resistance path for ground fault current to return to the source, the electrical service neutral conductor, in the event of a hot to chassis fault. This would also include anything plugged into the wall outlet. That includes the power cord feeding any equipment. Cut to the case, the breaker in the electrical panel that protects the branch circuit wiring will never trip open in the event of a ground fault event. // As for your power quality problem there is always a solution. It may require you hiring a certified credited power quality testing company. In my area they charge around $125 an hour. In your case the tech would be there about an hour or so..... He/she will have the test equipment needed to find your power quality problem. If it is coming in from outside your home the testing company will provide you with the necessary test reports to show to your utility power company. If it is inside your home the power quality company will identify the problem. If it is structure electrical wiring or fixed electrical equipment a licensed electrician will be required to make the repairs. In most cases the power quality company will recommend an electrical contractor company they use. Jim . |
stereo52,661 posts01-21-2019 6:16pm
I don’t believe anyone commenting here is a licensed electrician for your area nor knows your areas electrical codes. I would trust your licensed electrician before any of us. While everyone is trying to be helpful, we are merely speculating at best. If everyone got to you and you are truly worried, have a different licensed electrician come by to look at everything for a second opinion. It will be money well spent for your piece of mind.
I will bet you the AHJ in Chicago does not allow the equipment grounding conductor of an IG receptacle to be connected to an isolated earthed ground rod as the OP described the electrician did it. OP said: The other 20 amp outlet is grounded directly from the outlet to the outside rod with a clamp that is attached to the rod itself, I saw that with my own eyes. It is a straight wire that goes from the outlet to the outside and has nothing to do with the inside panel or anything else in the house. OP said: What is the difference between the ground wire that is connected to the panel itself and the one that goes to the outside, it still goes thru the panel but it is not attached to the panel itself it just goes thru the pipe that goes outside where the meter is and from there it is attached to the rod. // 2014 NEC® section 250.146 Connecting Receptacle Grounding Terminal to Box
(D) Isolated Ground Receptacles
Where installed for the reduction of electrical noise (electromagnetic interference) on the grounding circuit, a receptacle in which the grounding terminal is purposely insulated from the receptacle mounting means may be permitted. The receptacle grounding terminal shall be connected to an insulated equipment grounding conductor run with the circuit conductors. This equipment grounding conductor shall be permitted to pass through one or more panel boards without a connection to the panel board grounding terminal bar as permitted in 408.40, Exception, so as to terminate within the same building or structure directly at an equipment grounding conductor terminal of the applicable derived system or service. Where installed in accordance with the provisions of this section, this equipment grounding conductor shall also be permitted to pass through boxes, wireways, or other enclosures without being connected to such enclosures
http://www.cooperindustries.com/content/dam/public/wiringdevices/BuyersGuides/AHBG/I/AHBG-I-09.pdfWording is word for word right out of 2014 NEC, page 70-133. Nothing said about connecting the equipment grounding conductor to a ground rod. I see no NEC exception given for the OP’s electrician. I also doubt the Chicago AHJ would approve what the guy did either. It’s dangerous! Surely you would agree? AS for the OP getting another electrician out to house I agree he should. First thing he should do is land the IG equipment grounding conductor on the ground bar in the service electrical panel where it should have been landed in the first place. Then the OP should have the electrician inspect the rest of the work the other guy did. . |
@ tomiiv30 OPChicago? I didn’t think the city of Chicago AHJ allowed NM sheathed cable, (Romex is a manufacturer’s Trade Name for NM), in residential occupancies. My understanding all branch circuit wiring has to be installed in EMT conduit. Did the electrician install Romex? Is your house wired with Romex? Do you actually live within the city limits of Chicago? Jim . |
tomiiv30 OP33 posts01-21-2019 2:31pm
@cleeds
What is the difference between the ground wire that is connected to the panel itself and the one that goes to the outside, it still goes thru the panel but it is not attached to the panel itself it just goes thru the pipe that goes outside where the meter is and from there it is attached to the rod.
I am by no means an electrician and I am trying the understand as much as possible how everything should work.
The guy that came to my house and did this has been in business for over 30 years and I trust them thinking they know what they do. What is the difference between the ground wire that is connected to the panel itself and the one that goes to the outside, it still goes thru the panel but it is not attached to the panel itself it just goes thru the pipe that goes outside where the meter is and from there it is attached to the rod. @ tomiiv30 OP Like cleeds said that is an NEC violation. It is also not the correct way to connect the IG (Isolated Ground) ground conductor to ground. It can pass through a sub panel to the main panel the sub panel is fed from but it must connect to the ground bar in the electrical panel. Period! The problem with what you have now the earth is not considered a low resistive path for ground fault current to travel back to the source. In the event of a hot to chassis ground fault the chassis could/would be HOT with respect to any other piece of grounded equipment that is properly grounded within arms length. Heck, you would be better off just using a ground cheater at the outlet to plug the equipment into. At least then you know the outlet is not grounded. I am by no means an electrician and I am trying the understand as much as possible how everything should work.
The guy that came to my house and did this has been in business for over 30 years and I trust them thinking they know what they do. If the grounding is wired as you said, the guy is not an electrician either. He just passes himself off as an electrician....... Not all electricians are created equal. . |
atmasphere6,924 posts01-22-2019 10:38am
Amplifier buzz is a thing to fix- but it really shouldn’t have anything to do with the electrical system. @ atmasphere It’s not the amplifier that is buzzing loudly. It’s the power toroidal transformer buzzing, vibrating, loudly. It’s a big toroidal transformer capable of delivering 35 amps, continuous. At the vary least the torid would have to be at least rated at 3500Va. And that would really be pushing the torid beyond its’ limit using a 125% SF. In case you missed the OP post. He took the amp back to dealer. The service dept plugged the amp in, powered it up, and the torid transformer was quiet. No loud buzzing as the OP experiences at his home. tomiiv30 OP37 posts01-21-2019 6:26pm@stereo5
I still have the amp, a member of another forum sent me his two Emotiva CMX2 DC blockers and told me to put them in series and after doing so there is still buzz in the amp but quieter than without the dc blockers. @ atmasphere Any thoughts why the blockers didn’t stop the buzzing of the torid? Bad distorted waveform. Harmonics? . |
tomiiv30 OP37 posts01-22-2019 10:25am
Trying to fix the problem for this amplifier’s buzz it made a mess of my house electrical. I shouldn’t have done anything but just enjoy my new equipment, now we went totally different direction about fixing something that was not broken in the first place.
When I hire someone to do work I expect them to do all the necessary things, if they needed a permit they should’ve got one, and like I said everything was working just fine before I started adding outlets, even now everything works just fine and maybe everything is correct but I just don’t know that what I am saying is correct, maybe I am wording myself wrong.
This problem cost me so much time and money and nerves that is giving me nightmares at night. As for correcting the connection of one of the dedicated branch circuit equipment grounding conductor that is now connected to the isolated ground rod, that’s an easy fix. More time will be spent removing the electrical panel cover and replacing it. Connecting the equipment grounding conductor, wire, to the ground bar will take about 1 minute. Removing the ground wire that goes outside to the ground rod 10 minutes, if that. IF the electrician roughed in steel boxes for the new dedicated wall outlets there is a very good chance they are not grounded. Good chance he just connected the equipment grounding conductor to the ground screw terminal on the IG duplex receptacle outlet. The mounting back strap is not electrically connected to the equipment ground contact on an IG receptacle. Unless the guy connected the equipment grounding conductor to the box, as NEC requires, the box and back strap of the receptacle is not grounded. That would have to be checked and corrected if need be. Time to look at both outlets? 15 minutes. If they need to be grounded? 5 minutes each, if that. Material? Four green grounding pigtails and two wire nuts. As for the electrician/contractor pulling a permit. I doubt you will find many electricians/contractors across the US that will pull an electrical permit for installing a couple of 20 amp branch circuits. If the customer says he wants the contractor to get an electrical permit then the contractor will do so. Note the word contractor..... Being a licensed electrician doesn’t mean he/she can pull an electrical permit. He/she is also required to have an electrical contractor license for the city he/she is working in to pull a permit. (In my area an electrical contractor doesn’t have to be a licensed electrician. He/she just has to have a licensed Master A electrician working in a management position. Even if the contractor is an electrician, but not a Master A electrician he/she is still required to employ a Master A electrician working in a management position. Burning question! Is your house wired with Romex? What did the electrician install for the branch circuit wiring? Jim . |
@ tomiiv30 OP Your branch circuit wiring is more than likely installed in EMT (Electrical Metallic Tubing). https://www.homedepot.com/p/1-2-in-x-10-ft-Electric-Metallic-Tube-EMT-Conduit-853428/100400405 Per the NEC the EMT conduit is considered an equipment grounding conductor, Not sure if Chicago AHJ does though. I would imagine they do. Therefore per NEC the steel outlet box and supporting back strap of the IG duplex receptacle is grounded. Now I talked to another electrician just now and he said to me that the way green wire is done it is probably not up to code but he said that even they (then) it is should not be a problem.
Stop! Find another electrician! Keep looking. This guy sits on one of the NEC (National Electrical Code) boards that helps write electrical safety code. Watch the video. https://www.youtube.com/watch?time_continue=2&v=qNZC782SzAQ
Now what did the electrician tell you over the phone again? I know Chicago has good electricians. Jim . |
stereo52,670 posts01-05-2019 3:11pm
I hope Tom bought it from a very good dealer with a lot of cash flow. Some stores would be unable to refund that amount of money as many rob Peter to pay Paul. I hope for a happy ending. The dealer in my area has a no return policy. You buy it, you own it. And they are not small by any means. They probably have a million dollars of audition demo equipment and speakers in various rooms in the store. They probably sell more ARC equipment in the Midwest than anyone else. And yes they sell McIntosh. I asked the dealer, several years ago, why he didn’t have a return policy like the other dealer in our area. They offer a 7 day return policy. The dealer responded with another question to me. "What does he do with a returned piece of sold equipment?" "Repackage it and resale it for new?" "Put it on the floor and sell it as a demo?" Once it was sold and taken home by a customer it became used. And then he said something like, used is used. . |
4krow65 posts01-23-2019 3:17pm
And round and round we go. It’s this, it’s that, believe me. You made a simple case for me anyway. You took the unit to 3 different houses miles apart from each other with the same humming result. What more has to said? Defective unit, no? He took the amp to 2 other houses, not 3, and it buzzed. Was it as loud as it was in his home? I don’t remember if the OP said. He took the amp to the dealer where he bought it. It was put on a bench in the service department, plugged in, turned on, and no buzz. The OP said it was quiet. Defective equipment? No. McIntosh was just too tight to incorporated a DC blocker in the unit. Like I said in an earlier post I bet the design engineer designed it using a DC blocker. . |
clearthink607 posts01-24-2019 10:50am
If the claim that the amplifier was defective was valid, authentic, and genuine then why wouldn’t this person who came hear only to complain return the unit to McIntosh for repair, adjustment, or replacement and why wouldn’t he name the dealer who sold him this defective, damaged, or inferior unit? The unit IS NOT defective, When the OP took the amp to the dealer it was taken to the service department. There it was plugged in, turned on, and the torid transformer did not buzz/vibrate. The OP said the torid transformer was quiet. The OP was in the room during the test. Again, the torid DID NOT buzz/vibrate. It was quiet. So what good would it do to send the amp back to the factory? The amp is not defective. It works as it was built to function. If the consumer has DC offset on his AC mains the torid transformer will buzz/vibrate. The more DC on the mains the louder the buzz. Should the manufacturer have incorporated a DC blocker on the line side of the torid transformer? Yes. But the manufacturer chose to save a few bucks. Ron, a McIntosh representative, said they get maybe 5 complaints a year about mechanically buzzing torids. His advice to fix the CUSTOMER’S PROBLEM is to buy a DC blocker. Probably most manufactures that use fairly large torid transformers, in their equipment, install a DC blocker. McIntosh does not. . |
@ tomiiv30 OP I think the reason the DC blocker you got may not be working correctly is because it doesn’t have a large enough ampere rating. Does it give an, ampere rating on it anywhere? I believe you are going to need one that is made for a big power amp. There is an Agon member that used to build DC blockers. I will see if I can find his user name. |
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@ tomiiv30
Have you by chance sent a PM to gbart about building you a DC blocker for the McIntosh amp? . |
@ cleedsYou want to know so bad where the OP bought the amp why don’t you call the two dealers tomorrow and find out which one of the two sold the piece of cramp McIntosh MC8207 to Bill, the OP. As for sending the amp back to McIntosh what part of it would be a waste of time don’t you understand? The thing weighs 100lbs. What do you think it will cost to send that boat anchor insured back McIntosh and pay to have it shipped back insured? Hell, why don’t you and jetter step up and be good guys and pay the shipping + insurance cost to send the amp to McIntosh, both ways. Goggle search, Two McIntosh dealers in Chicago Illinois. Audio Video Interiors of Chicago 5.0 5 Google reviews
Home theater store in Oakbrook Terrace, Illinois Address: 1S550 IL-83 C, Oakbrook Terrace, IL 60181 Phone: (630) 607-0054 OR% Saturday Audio Exchange 4.6 49 Google reviews
Home audio store in Chicago, Illinois Limited-hour retailer offering a wide selection of new & used home audio systems & components. Address: 1021 W Belmont Ave, Chicago, IL 60657
Phone: (773) 935-4434 |
@
cleeds
Ron, a McIntosh representative, said they get maybe 5 complaints a year
about mechanical buzzing torids. His advice to fix the CUSTOMER’S
PROBLEM is to buy a DC blocker. Repeat.
His advice to fix the CUSTOMER’S
PROBLEM is to buy a DC blocker.
Why do you have a problem with understanding McIntosh's response to the customer? McIntosh knows the torid transformer buzzes if there is DC offset on the AC mains. So why do you continue to insist the OP send the amp to McIntosh? . |
DC blockers are colored and roll off the highs. BS! atmasphere6,979 posts
01-03-2019 1:06pm
DC blocking circuits are expensive to do right, and are very rarely needed.
That’s why they aren’t included in almost any linear power supply I know of.
You can find them on ebay for less than $100.00. We build them into all our amps. Repeat..... atmasphere said: We build them into all our amps. Bryston also does.
Bet there are plenty of others too.
. |
@ stereo5 As I said in an earlier post tomiiv30 needs to hire a Power Quality testing company to check the quality of the power in his home. Some electrical contractors may have the needed test equipment to preform the test, but most don’t. For many electrical contractors it is cheaper to hire a Power Quality company than buy the testing equipment. In my area a certified, qualified, power quality testing company charges about $125 an hour. A good single phase power quality analyzer can run around $10,000. And then you need a tech that is trained, certified, for its’ use. The tech will explain the problems, if any, and then recommend the solutions to solve the problem/s. If the power quality problem/s is coming in on the electrical service entrance conductors the tech will provide the necessary, certified, print out test results for the customer to give to the utility power company. Jim . |
cleeds1,989 posts02-08-2019 10:48am
Simply plugging it in to see if it buzzes isn’t the equivalent of a proper bench test. Agree. The AC mains voltage might be 115Vac - 117Vac at the wall outlet at the
dealer’s store. The OP’s mains voltage might be 123Vac, maybe 124Vac.
At the lower voltage the buzzing problem with the transformer may not
show up. . I’m not a robot. .
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