Mono Block Ground Loop

[eth2]

I have disconnected it, but not when all other electrical devices were disconnected. I will try this tonight and also buy the "widget" for the line.

[A1UC]

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[Chris Hornbeck]

There's another solution that might be easier for you. If you have a lightning protection power strip that includes cable protection (with F-connectors on board) just run your cable and all electronics' power through that. Within the lightning protection strip the cable's shield is connected to power's safety ground. This will also force a small local loop, and the large loops back and forth to panel won't matter.

The same thing can be done with a grounding block, as used outdoors before the cable enters your residence, with its earthing wire plugged into a safety ground (third wire) hole of your outlet strip - BUT this is not safe and not code, so don't do it. For clarity and info only.

All good fortune,

Chris

Edited April 17, 2014 by Chris Hornbeck

[babadono]

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Hey! It's a Jensen!

[babadono]

Eth2,

You don't have any of the audio/video from the cable TV going into or connected when you are experiencing the problems with the amps do you? If you do I have misunderstood you from the beginning.

[eth2]

No, I have disconnected it from the cable plate, but not from the main line.

[coolhandjjl]

Late to this topic. If you are still considering filtering your line voltage, don't bother with Furman or other devices. I suggest bridging a 15uF X2 cap across the white and black leads on the outlets you are using. You can get the X2 caps at rat shack.

Edited April 18, 2014 by coolhandjjl

[A1UC]

http://www.cullencable.com/index.php/products/power-filtering-products/perfect-plug

There are real nice also

[erik2A3]

eth2

You have worked hard on this noise problem! I have had similar problems in the last and can very much empathize with you. It can be frustrating indeed! Shorting amplifier inputs to ground is among the first potentially helpful things to try in order to determine the source, but I think you have done that.

What you are describing does not sound completely like the sort of ground loop interference I have experienced in the past but rather more like radiated interference -- EMI, RFI. RF may manifest itself in the form of faint music and dialogue filtering into your audio, but it can also generate other kinds of noise and interference where your cables, particularly if they are long and not well-shielded (or the equipment to which they are attached not grounded) will in effect act as antennae. Lifting grounds with cheater plugs can sometimes make this kind of problem even worse, not to mention dangerous in the case of vintage audio equipment with aging insulation: if the chassis is suddenly exposed to high voltage, and you have lifted the earth ground connection with a cheater plug, YOU now become the conduit to ground for that voltage trying to get to ground. So, the plugs can be useful for diagnostic purposes, but perhaps not always the best long-term solution.

Some have mentioned line filtering with capacitors across the the AC line. In the past people, particularly ham radio operators built sort of brute-force line filters consisting of a number of passive parts, but you should not have to do that. Many older amps also often were built with high voltage capacitors, usually ceramic, between hot and and ground and neutral and ground -- to deal with AC line transients. Dynaco and others would also install snubber caps across switches to absorb pops generated by power switches. I do the same on amps and preamps I have built. It works!

Moreover, ANY work on the AC mains in your house should be done by a technician. Or at the very least, a home owner who first turned OFF the current associated with the outlets, plugs, and switches in question. If you want to try to isolate your audio from your house mains, a very effective device can be purchased to do that and it's called a line isolation transformer. This is not a variac, by the way, which is not designed for line isolation.

With ALL the power cords of your equipment plugged into a common grounded, good quality power strip, and that power strip plugged into a nearby wall outlet -- you have noise, correct? Others mentioned dimmer switches, which can be an absolute pain. I once traced a buzz problem to the 3-position light switch on the vent hood over our kitchen stove. Although NOT the usual type of variable dimmer switch, which is essentially a volume control for the amount of light desired, the vent hood switch had Three FIXED positions, the lowest of which generated one heck of a loud buzz through our system. So, do you have any applicances that use switches like this on the AC line? Ceiling fans, fans or lights over kitchen or other appliances?

Do you have any fluorescent lighting in your house that may be in use when your audio system is being used, such as in a closet, utility room, or even fish tank? Fluorescent light can make terrible noise in some situations.

Have you used an outlet tester to confirm your outlets are correctly wired? Cheap and easy to do. You can get an outlet tester even at a grocery store, and it will tell you if a given outlet is wired correctly with respect to hot, neutral, and ground.

Is your house near any transmitting antennas? Mine is, and they have caused severe noise in the past. I usually install a very small capacitive filter between the RCA ground lug on the input to a component (such as an amplifier) and the nearest earth ground connection on the same component. If you are in an environment with strong RFI, what this little capacitor does is filter out very high frequency noise that may be riding on the shields of your interconnect before it gets into the audio. Boutique, high-priced caps need not apply for this position. Installation requires basic soldering skills and possible very minor chassis modification to obtain the required ground connection.

If you have other media in the room, have you completely isolated your system from it, including unplugging devices that may be on standby, such as TV, cable, etc.?

Check the ground connection for the house mains going into the house, itself. There will be a grounding strap or very heavy gauge wire connected to a copper clamp that is tightened against a long ground rod that was hammered into the ground near your house and service box. Make sure that connection is free of corrosion (think battery connections on a car battery) and that the wire is securely tightened in the ground rod clamp and the ground rod clamp is tight against the ground rod. FWIW: I use two copper ground rods hammered into clay, that are connected together. Check at the same time to check your Cable TV ground connections -- that they are tight and free of oxidation and rust. Confirm that the actual cable from the cable the box going into your house is secure, and that all other cable connections and splitter box connections are tight.

Hmmmm...what else....

[CECAA850]

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If it comes to this, I have one you can try before actually purchasing it. If it doesn't work, send it back to me, all you'd be out would be postage.

[eth2]

With ALL the power cords of your equipment plugged into a common grounded, good quality power strip, and that power strip plugged into a nearby wall outlet -- you have noise, correct?

YES. I HAVE TRIED TWO DIFFERENT TYPES OF POWER STRIPS INCLUDING A HIGHER ENDFURMAN.

Do you have any fluorescent lighting in your house that may be in use when your audio system is being used, such as in a closet, utility room, or even fish tank?

I DO NOT, AND I HAVE ISOLATED THE HOUSE TO ONE CIRCUIT BY CUTTING THE POWER AT THE MAIN BOX TO ALL OTHER CIRCUITS.

Have you used an outlet tester to confirm your outlets are correctly wired?

NO BUT I WILL PICK ONE UP. THANKS

Is your house near any transmitting antennas?

NO TRANSMITTING ANTENAS FOR COMMERCIAL RADIO/TV. I AM ON TOP OF A HILL, AND THERE IS A CELL TOWER ABOUT 1 MILE FROM OUR HOUSE MOUNTED ON A HOSPITAL ROOF. ALSO THERE IS A TRANSMISSION TOWER (68KV I THINK) ABOUT 50 YARDS FROM OUR HOUSE.

Check the ground connection for the house mains going into the house, itself

I HAVE LOOKED AND LOOKED FOR THIS GROUND. THE POWER COMES INTO THE HOUSE AT 75 YARDS FROM THE STRUCTURE THROUGH BURIED UNDERGROUND DISTRIBUTION. I WILL CONTINUE TO HUNT FOR IT.

THANK YOU! SORRY FOR THE CAPS BUT I THOUGHT IT WOULD MAKE IT EASIER TO DISTINGUISH. I HAVE ORDERED DI BOXES AND THEY SHOULD BE HERE LATER TODAY. I AM KEEPING MY FINGERS CROSSED.

Edited April 18, 2014 by eth2

[eth2]

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If it comes to this, I have one you can try before actually purchasing it. If it doesn't work, send it back to me, all you'd be out would be postage.

Thank you. I have already ordered one and thank you for your offer!

[joessportster]

Question for mark or craig

Couldn't this problem be that his VAC amps have such high gain they are amplifying small amounts of air born noise,and since his speakers are so effecient It is likely this problem with this particular amp style will never be quiet

as far as cable causing noise that is certainly possible, but easy to check simply go outside and disconnect the cable outside, if you still have the hum, Its not the cable and throwing more money at it wont help

Earl you have bose 901's try hooking them up and see how loud the hum is from listening posistion. If the hum is low or tolerable from those, I would suggest that you simply found an amp that is not ideal in your setup (it happens, not all amps are created equal for every setting)

Sent u a pm earl

[NOSValves]

Man this thread is a mass of confusion. I'm totally confused about what you have and have not done. I really hate to see the repeated statement "I order one". You need to stop and give me a call. I think too much is getting lost in the confusion of this thread.

We/you should not be concerned with your cable box at this point if the diagnostic procedure was performed step by step.

I thought you had run the amps with just the preamp hooked to it and had the noise? If so that is where you stop and look for a solution. Until the amplifiers and the preamplifier with no sources attached has achieved quiet operation adding sources just confuses the search for a remedy.

So I will ask... Have you run just the amps with the preamp and the noise was present?

[joessportster]

Craig not to but in here but early on in the thread Earl tried just the amps with pre in a couple ways, IE...rca,s connected, not connected, pre plugged in not plugged in, cheaters used not used

I completely agree spending more money is not the answer, Its a good way to go Broke

[babadono]

erik2A3, on 18 Apr 2014 - 04:15 AM, said: Have you used an outlet tester to confirm your outlets are correctly wired? NO BUT I WILL PICK ONE UP. THANKS

Just a word of caution/explanation about outlet testers. They will not detect a reversal of the ground and neutral wires. All other faults yes.

[babadono]

I thought you had run the amps with just the preamp hooked to it and had the noise? If so that is where you stop and look for a solution. Until the amplifiers and the preamplifier with no sources attached has achieved quiet operation adding sources just confuses the search for a remedy. So I will ask... Have you run just the amps with the preamp and the noise was present?

:emotion-21:

[NOSValves]

Joe,

Well I thought so....so my point is if the noise is present with just amp and preamp you stop right there...the problem is between the amps and preamp. I personally think it has something to do with the fact that the amps are primarily designed to run in a balanced configuration. If I was dealing with this problem the first thing I would try is a make shift ground strap between the preamp and amplifier. Second thing I would try is a balanced to unbalance adapter so I could try the balanced input of the amp. My bet is some grounding issue exists between the amps and preamp interface. The amplifier manual briefly mentioned issues can arise running an unbalanced source.

[coolhandjjl]

The fact that the noise went away when installed in another room is key. Transformer from a door bell. Metal vent in a chimney. Metal ductwork. Undischarged capacitors from other devices nearby even if unplugged. These are all things I look at when I have RF or EMI noise when I play my electric guitars.

I have a tri amp hi-fi system consisting of a mix of solid state and tube amps. Some amps are three wire A/C, some are older two wire A/C. Speaker efficiencies up to 110 dB. I have a barely detectable ground loop noise from one of the solid state amps. The tube amp has a tiny bit of either tube rush or EMI noise, possibly from my active crossover's transformer. (Not sure which it is)

However, I do enjoy the system.

Edited April 18, 2014 by coolhandjjl

[Guest David H]

In a previous statement, eth2 stated that if only 1 rca was plugged in the noise dropped. This is significant, and sounds like a loop.

On the amp with the rca disconnected, if you connect the center conductor only and not the shield is the noise gone and music playing?

I recently had a amp with the same concern and found the issue to be a bad ground, it also had no noise with shorting plugs installed. Mine was quiet with an ipod hooked up but not with my preamp.

From the pictures of the amp I see umbilical cords from the power supply , I also see a second outlet on the PS. What is the second port for? Can a single supply be shared? I assume you have run a ground between the power supplies.

When you took the amps to a different room did you take the preamp as well?

Dave

Edited April 18, 2014 by GotHover