Sounds like you have both unbalanced RCA inputs and balanced inputs to the monitors.There is no point in using the balanced inputs when the outs are unbalanced. Buy a small mixer with balanced outs. Plug the lappy into the mixer.

That link seems to show how to wire cables - but not specifically how to use unbalnced OP for balanced IP.

Could buy mixer I guess but trying to avoid more gear.

http://www.jensen-transformers.com/an/an003.pdf

Shows this I think, and seems to suggest some benefit from connecting unbalanced to balanced.

http://www.soundonsound.com/sos/1994_articles/aug94/groundloops.html

is also quite useful on the subject in general.

...still cant figure out why it used to be just fine though.

TOm

I found my problem and resolved it, and it had little to do with anything I thought of in the past.

I noticed that one keyboard was flickering on and off when I played it. I decided to change out the power strip. That power strip had 3 keyboards, a tremolo/Leslie effect stomp box, and another power strip that only the Wharfedale monitors plug into. When I changed out that power strip, I took out an older generic strip and put in one that has an indicator on it when a line fault is present. As soon as I hit the power button, the red fault light came on. Reset the strip, red light stayed on. Took that power strip to another outlet on another circuit, no red light. So I ran that power strip from a different wall outlet and now everything is quiet. So bottom line, the problem in MY case was a bad wiring job inside one of my walls, not surprising given what else I inherited when I bought this house in early 2009. NO ground lifts, no re-routing, just a bad wall outlet. Fortunately that wall is going to come down anyway and I will just eliminate that wire run.

But yep, everybody who said it was power conditioning for the few of us who talked about AC related hum was right on it.

And now back to the Stanley Cup game.....

"I removed the earth/ground connection from mains lead on the suspect unit - hey presto - no hum - all works perfectly - except risk of getting fried if goes faulty."



Seems like a ground loop issue if you lift the ground and all is well. If you can't track it down, take a look at some of these products that are made to help these situations-

http://www.musiciansfriend.com/navigation?q=ebtech

And also-

http://www.musiciansfriend.com/navigation?q=power+conditioner

Good luck.

Dan

Eddie, I once managed a computer center, and we wondered why the life of the electronics in the display area was so short. Because of the faulty wiring, anything that caused the equipment to be connected to more than one outlet, like a shared switched printer for many PCs, allowed substantial stray voltages to flow. A new wiring job for the whole wall was needed, and after that, no problems.

The first thing I do before plugging equipment in, is take out my three-prong outlet tester. These testers are cheap, like $5, but they can quickly save you time and money.

I worked for 8 years with one of those 3 prong testers in my pocket. A fire inspector should have tools. I also had a proximity tester and another one I could use on stainless steel in restaurants to detect stray voltage. People said to me, I got tingling from that thing for years and now it's gone. Go figure.

In a burned out building don't touch the bare phone lines. As long as no call comes in you are not like the electrocuted cat in the cartoon. It may not seem like lots of volts but you only do it once in a wet basement.

John, when you say proximity tester, is that the thing that you can just touch to the outside of the wire and see if it is live?

I have my electricity guy coming in later this week for something else and I am going to have him look at every circuit upstairs. He rewired my basement to add circuits for the woodworking shop and kicked me up to 200 amp svc because I was also adding an electric range. Before his visit, if I ran the shop vac to catch the sawdust when running the table saw I would blow a breaker. He added 6 outlets in the basement, each on their own 20 amp breaker. Need him to nose around upstairs now. The hum was cut 85% by moving it to the other circuit. Of course I would like dead silence. Much like the audience wants when I sing....

Well as an Electrical Contractor & Chief Electrical Inspector IF you want dead silence what you need to do is isolate your studio circuits from the rest. The only way to do this is have an Electrician run a 50A/220VAC circuit to an isolation transformer and from the trans former to a new panel.Then individual branch circuits as needed from there. The grounding electrode systems is re established at either the transformer or the new panel depending on the wiring configuration and in essence provides you with a new SERVICE that is just for the studio.

Thanks John. I had a feeling that for perfect silence I needed perfect wiring for perfect power. I will have my guy give me some numbers for that. When he worked on my basement 2 years ago he did a lot of work (New panel, upped the service to 200amp,and put in 6 new outlet boxes, as well as removing 2 very bad pieces of home made wire run form the previous owners) and did me okay on the price.

Great to get input from an actual professional like yourself! I freak out when I change light fixtures! Took me 6 years to work up the courage to remove a 1960s ceiling fan/light fixture and replace it with a florescent. Took 15 minutes, went without incident, but still took 6 years....

Don't even ASK me about plumbing.... LOL!!

Another way that may be as effective in the home is to wire the studio using all metal boxes and Medical Grade AC Cable. AC cable otherwise called Armored cable is UL listed so that the armor can serve as the equipment ground. It looks similar to the old BX cable but is not at all the same. The medical Grade also has an insulated grounding conductor run inside with the other 2 conductors. Patient Care rooms per Art 517 NEC requires redundant grounding. In the case of the studio you'll use receptacles that have isolated grounds. In this way the boxes are grounded with the armor of the cable BUT the ground on the receptacles is done with the insulated equipment ground.This way the armor actually acts as a shield preventing stray currents & EMI from getting in.Mention both methods to your Electrician. If he has that "deer in the headlights" look find another Electrician.

I sincerely doubt this is caused by an AC ground problem.

A licensed electrician should be called in to make good and sure that the Line and Neutral are not reversed somewhere in the home wiring, or worse, a Shared Neutral...


--Mac

I think it can also be a load balancing issue.

This means that for the load on one side of the neutral, there should be close to the same load on the other side.

Know what else is weird/interesting? The way this neighborhood is wired, I have had times when there was in issue on a pole on my street and only HALF of my house was out. Apparently this street is fed from 2 sources from 2 different streets, because while the outlets in the living room and 2 bedrooms were dead, the kitchen, 2 bedrooms and bathroom had power. Strange, eh? Neighbors had the same condition. Half the house was live, half the house was dead.

That sounds wrong. It sounds more like you lost a phase.

However, if all the houses do that, maybe you live in a development where they were intentionally wired this way, and you have two power meters.

I would contact the power company.

I talked to the guys when they were working on the problem. He explained that one 110v leg came from one transformer and the second 110v leg came from another, on the next block. Nobody could explain WHY, and most people don't even believe that this condition existed, but the living room was dead, thus the power strip that feeds the TV and Direct TV box had no power. However, the cable modem and router, plugged into an outlet in the kitchen, were live because I was still online on my laptop, though it was on battery power because the living room was dead. When I ran an extension cord from a kitchen outlet to that power strip, I was watching TV. 2 hours later the room lights came on, the lights and fan in the living room came on.... it was truly THE strangest thing I ever saw. And it piqued my curiosity to a point where I walked around with a lamp during the half outage and tested every outlet, making note of what worked and what didn't. When the power was fully back on I went downstairs to the breaker panel, and everything that worked was on the the RIGHT side of the panel, where everything that did not was on the LEFT side of the panel. Now when my guy was in, he explained that he changed a few things around to simplify the wiring and eliminate any "crossing" in the routing, so it was clear to see that one leg feeds the left and the other feeds the right.

Now, to the power expert (is it John that is the electrical contractor guy?), should I be asking the power company people to change that or not? The way it is now I will apparently always have power to at least half a house..... Is there any actual danger or practical reason to change it? Since it was the whole lower end of my street that had the same condition, it would seem that it was wired that way on purpose. I don't even know how I would explain this if I called the power company.

I'll bet the power company will be quite interested.

As far as things coming back later, I have read about phase problems where you regain power when something that is 240 volts, like a range, is turned on, allowing power to cross to the other side of the panel. It's not a mystery to someone who knows about this problem.

The phase thing is simple. I doubt what you are being told is correct, if anyone who understood transformers stood and looked at you nearest one they could figure it out,
However you have 120 v from the one side of the fuse or breaker panel to the middle (neutral).

If you go from one side to the other not using the neutral you get 240 v.

There are 3 wires coming into the house. One is the neutral, the other are the phases.

There should be roughly half of the breakers or fuses on each side, the stove for one straddles the two.

When one phase goes out, either a transformer or feed wire failure, only 1/2 the panel is live. The stove crosses over. You turn on the stove and you feed, based on the variable nature of the switch, power across to the dead side. It does however flow back out towards the break to a degree, but through your dead side, so if you have lights on it will act as a dimmer switch.

I've had this happen twice in recent years and when I call up and tell them a phase is out they usually get the attitude wtf you know about that old man? Nice.

If I'm maybe wrong I usually don't open my mouth and prove it is all.

Or I tell you the story about one time...never mind.

There is a well known situation that can happen with the 2-phase 240 wiring setup that is dangerous.

If the two sides that are 120V in respect to a single Neutral wire lose that Neutral connection somewhere, appliances end up running in SERIES with each other. This is not good at all, as one appliance's resistance may be higher or lower than the other line's appliance(s), resulting in all sorts of voltages other than 120 going to each. Could be higher than 120, could be lower.

Another situation, one that I suspect in this "mysterious" case, is that somewhere in the house wiring the Line and Neutral have been reversed. The wider blade of the socket should always be the Neutral and the Neutral should also always be Grounded back at the panel. If someone installed a socket and did not put the White wire on the Silver screw and the Black wire on the Gold screw, but instead reversed them, this could be the rather dangerous reason for that one speaker humming like that.

In either scenario, or whatever, the house wiring should be inspected by someone who knows what they are doing - pronto.


--Mac

Edit-

Never mind.

Dan

I am not an electrician and dont know very much but you might try a mains smoother - it cleans pu the cycle in the AC.
I might say I have a studio a long way from the house and its wired by an electrician competently, but I get a hum on my speakers - it was suggested that I tried this - I did but it did not work for me. I think that my equipment is running on low powere due to the length of the cable to the studio - 40 metres.