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Thread: New space, Amps all hum now?

  1. #31
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    A BAD SHOCK! YOU BET! I wouldn't dare replace a grounded cord with a nongrounding cord! While I was attending an amateur musical program one evening, a couple of fellows set up their two amps and guitars to play and sing a song. When the lead singer grabbed the mike stand of the mike belonging to the house as one might casually do, he was shocked so badly that he fell off the little stage. That was in the era when amps didn't have the grounded cords; for one thing, if a short developed between the chassis of the amp and one side of the AC line cord, then you have a 50/50 chance of the chassis sitting 120 volts above ground. In those days, there could be a shocking voltage between two guitars on separate amps or as in the case I knew between the guitar and the house mike, which was probably well grounded while the amp for the guitar was not. We should never defeat the polarized plugs on line cords or on those cords with a third wire as a ground.

  2. #32
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    "Bad earthing on the power supply...." If the hum didn't occur in the original location, but now it does, I wouldn't suspect the power supply in the amp(s). With the same hum in both amps, I would have to suspect something outside of both amps, since it is not too likely that you would find the same hum-producing in both of the amps.

    Something "weird" just occurred to me: I note that you moved the amps downstairs to a quieter location. Of course, I don't know how bad the hum is, but could it be that at least some level of hum was present in your original location, then when you moved the amps to the quiet location, you now hear that hum? I know that was a strange consideration; but when we are troubleshooting a difficult problem, we should consider at least briefly all the possibilities of which we can think.

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  4. #33
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    Lots of good ideas here. In Radio studios and even those apartment studios the ground was done through a 6 foot copper rod sunk into the ground.

    I myself would start by disconnecting the input that eliminates the hum coming into the amps- if no hum then it is getting into your input signal path.
    OLD houses can have different ground potentials and this due to clamping on electrical pipes that has gone bad will make ground loops. I forget the wall ground and make a star pattern ground on chassis with thick wire. This way if a wall ground is floating it will be grounded through the star pattern.

    Running audio cable that is not 100% shielded will allow all kinds of interference into the signal line. The question is why are you using this kind of cable if you
    want a good result- that spiral wound drain wire 50 cent cables should be eliminated in all cases. Throw it out.
    Some of the test bench connections I have made using RG6 3GHz coax- it is also low capacitance or it would never handle 3GHz. The low cap and 100% shield is what I am after.
    I use to buy cable4less 6 foot ones but they stopped carrying them. I think Monoprice cables are the next cheapest BUT good cables to get- I look for those that can carry 50KHz without loosing more than 2 dB as measured by my equipment. The Cables for less cables did meet that spec. I found out by cutting one they are not coax but more like Canare cable with two conductors in them but shielded well.
    Best regards,
    Skywave Tape Deck Repair, Chicago area

  5. #34
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    Quote Originally Posted by skywaveTDR View Post
    Lots of good ideas here. In Radio studios and even those apartment studios the ground was done through a 6 foot copper rod sunk into the ground.

    I myself would start by disconnecting the input that eliminates the hum coming into the amps- if no hum then it is getting into your input signal path.
    OLD houses can have different ground potentials and this due to clamping on electrical pipes that has gone bad will make ground loops. I forget the wall ground and make a star pattern ground on chassis with thick wire. This way if a wall ground is floating it will be grounded through the star pattern.

    Running audio cable that is not 100% shielded will allow all kinds of interference into the signal line. The question is why are you using this kind of cable if you
    want a good result- that spiral wound drain wire 50 cent cables should be eliminated in all cases. Throw it out.
    Some of the test bench connections I have made using RG6 3GHz coax- it is also low capacitance or it would never handle 3GHz. The low cap and 100% shield is what I am after.
    I use to buy cable4less 6 foot ones but they stopped carrying them. I think Monoprice cables are the next cheapest BUT good cables to get- I look for those that can carry 50KHz without loosing more than 2 dB as measured by my equipment. The Cables for less cables did meet that spec. I found out by cutting one they are not coax but more like Canare cable with two conductors in them but shielded well.
    While all good suggestions, the OP has already said that he has a professional electrician doing all of the wiring. He also just recently added this area's own ground connection. We should hope this electrician knows his craft.
    Last edited by FingerzAndKeyz; 1 Week Ago at 14:12.
    Music ~ the International Language

  6. #35
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    I do want to make one point, since you are now thinking of just living with the hum. That might be out of disgust or humor, but either way, don't do it. There is a solution to this. BUT, you really have to look at it from the beginning.

    We're now hearing there is a new router? That wasn't in the original post. What we heard was everything was the same, just at the other end of the house. True, the water heater could be an issue. I don't have that, because mine is 30 feet in front of the house, at the street. Sorry, my own version of humor.
    Last edited by FingerzAndKeyz; 5 Days Ago at 07:55.
    Music ~ the International Language

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    I seem to have got it down to the router or water meter, will be doing some investigations tomorrow, when my wife is out all day and the internet can be down for a while.

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