The white one #14 NM-B feeds front projector.
Breakers are 30 amp., I don't know, why he used them.
The cable runs are approx. 50-60 ft. ?
I also see one orange 12 awg. cable entering the sub panel- the black (hot ?) wire is not connected to the breaker, terminated with the cap, the white and bare ground are connected to corresponding bars. What's that about, I don't know. Could that cause a problem?
In any case, I'm back to square one. What else can I do??? |
Well,
I already tried turning off all circuit breakers, no help.
Tomorrow I'll bring the amp to the living room to try with another pair of speakers and another outlet.
I have two other pairs of less efficient speakers, so I'll give it a try as well.
BTW, what's your take on the high chassis voltage, higher with the correct polarity? |
Hanaleimike,
I'm a little late to this discussion, but anyway, here is a question for you:
When you said: " I would think that if each receptacle has it's own run via a 12/3 wire , all the way back to the panel on a separate ground bar in the panel, that there couldn't be any ground loops. I think the ground pin in the receptacle runs back to the panel, and the receptacle itself is grounded to the metal box. It sure made a difference sound wise too."
Specifically " separate ground bar in the panel"- did you mean, that there is supposed to be a separate ground bar for each dedicated line?
I understand, there is only one ground bar in the panel. Could you please explain that in more details?
I always been somewhat confuzed about the term "isolated ground"- isolated exactly how?
The reason I'm asking is this;
I have licenced electrician to install separate panel with five dedicated lines connected to it:
One for digital,
one for analog,
two for power mono blocks,
and one for video projector
He used Romex 12/3 wire, and to my understanding, at least, that's how I asked him to do it, ground wire from each receptacle (actually there are two receptacles on each run of wire) is connected to a ground bar in the panel, and the ground bar is connected to a copper ground rod right next to the panel, and to a common house ground elsewere.
Still, I have a ground loop problem somewhere.
Even when just a power amps connected to the speakers, and nothing else connected to the amps, and with grounds lifted on both amps with a cheater plugs, still I hear faint hum (much louder with no cheater plugs).
I have tried everything:
Unplugged every piece of equipment, and turned off all circuit breakers,
Lifted grounds on every single piece,
There is no cable, or TV on the same circuits,
Disconnected copper ground rod, installed along with the new lines, from the panel-
still, there is ground loop somewhere.
Now, I suspect, there is something wrong with how the ground wires from the dedicated lines are connected to the panel.
Unfortunately, I don't know of any audiophile electrician in my area, who could sort out the problem, and my "regular" electrician apparently has no clue.
Please, could somebody explain how to correctly ground my five dedicated lines, and how exactly "isolated grounds are created?"
Thanks in advance. |
Ozzy,
They are physically on both sides of the panel, I'm not sure it electrically corresponds to an opposite legs, or not. I will have to check that later tonight.
I tried to plug it into one outlet, stll hums. |
Jea 48,
Sub panel is connected to the main one with 4 AWG wire, with Black, White, Red and naked copper ground conductors.
Breaker in the main panel, feeding the sub panel is 60.
The wire he used for dedicated circuits has Black, White and naked copper ground conductors, so I guess, I mistakingly called it 12/3.
All five dedicated circuits feed 5 duplex receptacles, that is correct.
I don't think, that the ground bar in the sub panel is isolated from the panel metal enclosure.
Yes, sub panel ground bar IS connected to the main panel ground bar.
Also main panel ground bar is connected to an additional
copper rod, installed at the same time, as the sub panel.
And one more thing: I noticed, that a small connector box with TV and Internet cables, has a ground wire, connected to the main panel ground bar.
I have two questions:
1. When evrybody says "isolated ground" does it mean ground bar in the panel isolated from the metal enclosure?
And, if it's not isolated from the panel (like in my case, it seems), would that be a problem causing ground loop?
2. You'd have to forgive me, but I'm not entirely clear about the last part of your post;
"More than likely here is your problem. Just bet you have a difference of potential, voltage, between the equipment ground at the receptacles and the neutral, the grounded conductor.
Per NEC the feeder equipment grounding conductor shall be installed in the same cable, or raceway, as the feeder current carrying conductors. And the equipment grounding conductor shall terminate in the same panel the feeder is fed from".
And how exactly should I correct this problem?
Thanks a lot for taking your time- it's really priceless. |
Ghstudio
I tried to disconnect it, no effect. |
Actually, I just wanted to post about something I did last night-
I moved amps L to R, and the hum moved as well, but I have also noticed, that a level is lower on the side of a humming amp (center image moved to the opposite side),
I double- checked moving it back, there is disbalance.
So now I'm strongly suspecting there is something buzzing inside the amp. I'm going to ask my friend, if he wants to take it to BAT for check- up.
Question- what internally can cause this kind of buzzing?
Cap, resistor, bad tube?
Amps are self biasing |
|
Jea48,
As I posted above, there a pictures of the panel, that should answer some of your questions.
4 AWG wire is not in a conduit, it's the thick white one in the picture, and the bare copper ground is inside of the white insulation, with the black, white and red ones.
The run for the 4 awg is just about 3-4 ft.
3 of the hots appear to be connected to the L leg, and the other two to the R leg (see pictures).
Polarity in the receptacles is fine.
What do you think about ground from the cable connector box?, it's the green insulated wire going into the main panel from the left. (see pictures). |
Jea48,
I will have to look at that screw when I get home, but what are you thinking about?
There is no CATV cables connected to my audio system.
The only video cable, is DVI, connecting DVD player to the front projector, and disconnecting it doesn't change anything.
As you probably noticed, the amps and preamp are balanced design, could that be a culprit?
I have a computer in the same room, but it's not connected to audio in any way, and is on a different circuit electrically. |
Jea 48,
Just last night I did another experiment- connected both power amps and preamp to a single outlet with a power strip, no cheater plugs- faint hum in the R channel and louder hum in the left.
Funny thing is, that I have the same model power amp before, just in stereo configuration (BAT-75 SE), and had the SAME problem, hum louder in the L channel.
I am absolutely sure the amps are fine, they are on loan from my friend, and are absolutely quiet in his system.
I didn't take them to my living room system to try, just because they are so heavy.
I will try again with no ICs connected, but then I'd have to use plugs in the inputs, otherwise they pick- up noise as antennas.
Ghstudio,
I'm pretty sure my electrical is up to code, as Jea48 seems to agree with. |
Just did it again- no ICs connected, plugs in the inputs- same hum. |
Jea48,
First to answer your question- If I understood you correctly, you are asking if the hum is less with ICs disconnected?-
No, it is not.
Can I use a polarity checker, kind they sell in Home Depot, to accomplish the same, unless you meant to do this test for a purpose, other, than to check polarity of each receptacle?
I cannot understand one thing, though- how come the hum is louder in one channel??? |
Got you,
Here are the measurements.
Meter set at ACV 50
Left amp: Right amp:
Right cheater plug: 38 37
Reversed: 33 30
So, what's the verdict? |
The answer to the big question- no, hum is the same after AC plug is reversed |
Just realized my meter settings were at 50, instead of 250 V
new measurements:
L amp:
Correct cheater plug 62.5 V.
Reversed 51 V.
R amp:
Correct 62.5 V.
Reversed 51 V. |
OK,
Neutral to chassis- 0 v. on all meter settings
Hot- Neutral 120V.
Hot to chassis:
Power cord unplugged 25 V.
Power cord plugged-in, amp. is OFF- 112 V.
Power cord plugged-in, amp. is ON- 90 V.
As usual, I have no clue, how to interpret all this. |
|
Al,
Yes, that's what I'll try tonight. |
Got you,
Hot- Neutral 120 V.
Hot- Ground 120 V.
Neutral- Ground 0 V.
With the amp. ON- Hot - Neutral 120 V.
BTW, thanks a lot for your patience. |
Almarg,
Yes, you're right, I'm talking about my friend's 150s.
I no longer have 75-SE, but am considering buying it again, that's the whole reason for this post.
VAC didn't have this symptoms, just some ground loop, that I corrected.
The hum is mostly coming from the tweeters, but can also be heard from mid and bass drivers.
Just a little bit of history: what started me on this wild goose chase, is a significant hum coming through the speakers with a phono input selected- I could see woofers moving.
In another lenghty troubleshooting session with Kevin of KAB, we narrowed it down to phonostage amplifying some AC interference. I could also hear phonostage picking-up a radio signal (actual radio broadcast).
All this information combined with BAT's bandwidth, gives your theory an extra credit.
I will experiment with computer and radio tonight.
Shorting plugs- I don't know how exactly they are wired, I'll look into it.
Thanks for your help. I hope you, Jea48 and others will hang with me for a while longer, until this gets resolved, or I commit suicide. |
Jea48,
I will check the power cords tonight.
Al,
Now, that you said it, I do have wireless router next to my desktop computer in the basement, transmitting to my wife's laptop, she's using in the kitchen upstairs. Transmitter is closer to the L channel amp. Also, Comcast cable goes along the same left wall to the desktop in the back of my listening room.
Can't wait to get home tonight and disconnect all that crap, to see what happens.
Will keep you guys posted. |
Don't know where to begin, well:
I was hoping to find interference from my PC or cable, but no luck. I disconnected and unplugged PC, cable modem, wireless router, switched off all breakers, except the power amps- hum is still there.
Tried different speaker- still there
Tried different power cord- still there
Plugged the amp into a different outlet upstairs, separate from the dedicated panel, through the long extension cord- still there.
Hum, or buzz, is very constant in nature and nothing seems to change it. it does sound like a ground loop buzz to me, more, than anything else.
Again, L channel amp hums more, than the R channel with everything disconnected from it.
Hevac1, thanks for your ideas, but in lieu of the above statement, I don't think compatibility of the different components is the culprit.
Jea48,
I don't know why I didn't ask him to move GFI breakers (they are the ones with yellow markings on them?).
Where do you think they should be in the panel?
Did I mention how frustrating that is ? |
One last thing- I switched the amps left to right, and the hum moved too. I don't know, maybe it's inherent to that amp? At any rate, hum is there. |
|
Well,
It's not tubes, at least not the power tubes. I switched them around, hum stays with the same amp.
I guess, BAT will have to take a look. |
