I just want to mention....... W/ my phono amp I had hum I could not resolve. Moving the amp out about 3 inches from the position it was in cleared the issue!!!!!
My phono amp is point to point (my first p2p), so I was SURE it was an issue I created. I re-wired that amp countless times trying to repair it. I gave up.
one day while moving things around in my living room the hum went silent! After investigation I figured out that literally, about 6 inches forward placement of the amp removed the hum!!!! I still have no idea why. There are no high voltage wires running past where it was sitting, or anything.
My phono amp is point to point (my first p2p), so I was SURE it was an issue I created. I re-wired that amp countless times trying to repair it. I gave up.
one day while moving things around in my living room the hum went silent! After investigation I figured out that literally, about 6 inches forward placement of the amp removed the hum!!!! I still have no idea why. There are no high voltage wires running past where it was sitting, or anything.
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I solved a problem like that in the same way once. You'd be suprised to learn how far a power transformer can throw an EMI field. I had a turntable about 18 inches away from my amp and had low hum on the phono input. I was shifting my stuff around and found the hum got louder and softer as I moved the amp around. The magnetic cartridge was getting hit by EMI. Had nothing to do with the phono ground line which was good. Unbelievable.
Illegal?
Hi Guys, neutral-grounding is almost certainly illegal and can be dangerous. Loss of neutral, upstream from the outlet, will put the outer surfaces of any equipment supplied by that outlet at AC Line potential. It can create severe hum because, under heavy circuit loading, the couple volts drop in the current-carrying neutral wire will be on the chassis of audio equipment supplied by the neutral-grounded outlet. A "don't try this at home" in my book!
Hi Guys, neutral-grounding is almost certainly illegal and can be dangerous. Loss of neutral, upstream from the outlet, will put the outer surfaces of any equipment supplied by that outlet at AC Line potential. It can create severe hum because, under heavy circuit loading, the couple volts drop in the current-carrying neutral wire will be on the chassis of audio equipment supplied by the neutral-grounded outlet. A "don't try this at home" in my book!
Sorry to hear that. I have a few (too many) Technics DD's and haven't had motor noise. Sometimes the 4 contacts inside the arm at the headshell get a little corroded. Maybe not providing a good contact on th (-) of one of those. The cables take a lot of abuse where they pass through the base, too. An intermittent conductor there will pick up hum for sure.
Heh, me too... 5 of them!
(obviously was in to electronic music, dj'ing etc in my past) Wiring wasn't the issue. Thinking about it again I'm guessing it's interference from my other amps. They're arranged vertically shelves. Phono on bottom, then pre, then main amp above that. I'd guess some interference was radiating down from the pre's PS, above the phono.
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Hi Guys, neutral-grounding is almost certainly illegal and can be dangerous.
A "don't try this at home" in my book!
I hesitated to suggest he call the local electrical inspector and ask about it. He'd probably want his address and the name of the electrician.
The amp has four KT-88 output tubes, four 6SN7 tubes and two 12AX7 tubes. Rectifier........does that have something to do with Preparation H?
After turning up the bias, the amp would make a high-pitched whine during warmup only. Not through the speakers.....the amp was making the whine.
I am hearing, and partially understanding, the discussion about grounds and neutrals and input devices perhaps having floating ground values.......and what I'm hearing is basically that some of these devices, chassis' output/input circuits may be carrying voltage. The message to me is to be careful, and perhaps power everything down and unplug it before touching. Did I get that right?
Also, if I unplug everything when I get home, then power the amp up using a proper, 3-conductor outlet, and do the same to input devices, there is a chance the hum will not reappear? I'd be happy to do that.
It's a serious breach of the 17th IEEregs in the UK. Also Elec At Work regs.
Regards
M. Gregg
I had issues w/ the neutral at my home (issue at the TX up on the pole) and it introduced hum.
After that issue was corrected (for free by the electric company) all the hum issues I was having at the time were resolved.. (other than the phono thing I mentioned above).
And, in that case, yes, having all amps, and all sources connected via 3 prong plugs, properly grounded and neutraled, solved my hum issues. (again, other than the weird phono thing)
and if you're wondering how I determined the issue was w/ my neutral at the transformer on the pole.....
I could measure about 7 volts between my neutral line and the concrete floor of my basement! (actually, I measured between the neutral of an outlet, and the metal drain cover on my basement floor)
I called the power company once and told them I discovered the problem, and they wouldn't do anything. I called back the next day and lied and said an electrician tested it, and they immediately sent someone out. He said he'd never seen such a "messed up transformer".
I could measure about 7 volts between my neutral line and the concrete floor of my basement! (actually, I measured between the neutral of an outlet, and the metal drain cover on my basement floor)
I called the power company once and told them I discovered the problem, and they wouldn't do anything. I called back the next day and lied and said an electrician tested it, and they immediately sent someone out. He said he'd never seen such a "messed up transformer".
FWIW, this house is built like Fort Knox. Not saying there couldn't be problems, but the guy who built it in 1953, then sold it to me a few years ago, made nothing but good decisions. The finest of everything. The connecting of the green ground screws with the neutral circuit on the outlets appears to have been done by an electrician. Or at the very least, someone with wiring experience. Workmanship appeared to be high. Still.....ground circuits should be independent back to the service box and I have the capability to retrofit the proper cabling.
The amp is in fairly close proximity to a CRT television and some other electronics gear. This was also the case when the hum was absent. This all happened when I moved the entertainment center two feet to the right.
The amp is in fairly close proximity to a CRT television and some other electronics gear. This was also the case when the hum was absent. This all happened when I moved the entertainment center two feet to the right.
Okay then. Thank you. I will commute home with an experiment on my mind and hope in my heart.
I just re-read your question...
basically, your neutral (lets say 2nd prong, not the 3rd earth ground) carries all the negative potential of your home. If your chassis is connected to neutral, not ground, then if you touch that and offer a shorter path to ground for some reason, it will go through YOU. So yeah, you should never have your metal chassis connected to neutral, or the 2nd prong. Ground is supposed to be ok.
(Personally I still have issue w/ all of this in the USA, because ground and neutral are connected to the same place in your circuit breaker box, but whatever.. lets just ignore this comment for now)(I guess this gets down to literally the "shortest" (and least resistant) path)
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At the box there is supposed to be a short run heavy copper ground puting the common lugs and the safety ground lugs at ground potential. That would eliminate any ground looping potential to return to a chassis. But of course if there is much distance to the true earth then there is going to be some weak ground loop possibilities. And if commons and safety grounds get interconnected somehow prior to the panel then all bets are off.
Please don't do this! If a neutral connection fails anywhere between that outlet and your panel you will have the full iine voltage on your chassis.. Even if it doesn't any IR drop in the neutral will impose a significant AC voltage on the chassis and this is hazardous. This has got to be a violation of the NEC, and might have insurance implications as well..
Some former lame brain did this in my house (before I got here) and I almost got electrocuted as a consequence of an appreciable ac voltage developing between neutral and a real ground I happened to touch while using my supposedly "grounded" solder iron. It hurt a lot..
Some systems using old 2 wire BX use the metal jacket for safety ground, not totally reliable if clamps get loose over time, however it is safer than using the neutral for this purpose.
Get an electrician (in some cases you can do it yourself) to run a new line of 2 wire + ground Romex or BX to the outlet(s) in question. Ground and neutral may be tied together at the panel, but nowhere else.
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I grok, Kevin. I've done substantial remodeling downstairs where most of the ceiling is still open, so I have fairly good access to the upstairs wall cavities (after drilling holes in subflooring) and good, 3-wire cabling. I have seen voltage anomalies all along, so re-wiring those outlets is necessary and I will do that.
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