Mono Block Ground Loop

[babadono]

Bobadano,

I made dummy plugs as you suggested and used them. I have reported the results. So if the dummy plugs test for the same thing as the alligator clip test, I guess I should not bother?

I thought you only made shorting plugs for the amp inputs. The dummy plugs are slightly but only slightly different.They have a male and female end so you can put on inputs and outputs and the open ends of cables.

[eth2]

Bobadano,

You are right. This is a job for my engineer friend. If I had been good in math, physics, etc., I would have entered a "real profession" as my engineer friends call their jobs.

Mike,

As for the humidity, if it is relevant it is because high humidity decreases the effectiveness of an insulator on the pole. As you probably know, that is why on a humid night you can hear the high tension wires crackling and singing. Early in my career I was allowed to work with the "Live Line Maintenance Crew" for a few weeks as part of my introduction to the company. We would bond on to a 500kv line with a pole and dressed in a special wire suit (Fermi's cage principle) so that we were at the same potential as the line, They changed out insulators on those 500kvwhile the lines were energized. Those guys had balls. Doubt if Amazon has a high enough capacity dehumidifier to help.

Edited April 11, 2014 by eth2

[eth2]

Called NYSEG. They are going to have someone check he lines next week.

[USNRET]

When I lived on Padre Island the salt water spray had devastating effects on the insulators. Occasionally, the power company would have firs truck hose them down with fresh water. I ended up buying a APC UPS to protect the tube gear from power cycles as I lost a couple of tubes from hot cycles. The power company put a real time transmitter on my house and verified that I was dipping into the low 90 volt range.

[eth2]

Occasionally, the power company would have firs truck hose them down with fresh water.

Sure hope they took those lines out of service before the fire trucks washed them down.

[A1UC]

Not sure if anyone has mentioned this, but the main solution to my Ground Loop Problem was to have both Monoblocks Plugged into the same outlet, not the same circuit.

Even though I had a completely separate dedicated circuit. I would get a ground loop hum with the amps plugged into different outlets. All it takes is a couple milivolts of different potential between outlets and that is enough to magnify and pass it on to your speakers. The monoblocks were 12 feet apart, so what I did was run an extension cord to plug the other amp into the same outlet. Luckily I built cabinets along a wall where I could hide the cord under a false bottom of the cabinets.

I'll attach a picture of my room, where you can see how far apart the Monoblocks are. The base of the wall cabinet is open for running cables etc.

Awesome Room Cut-Throat I'm Jelly Best of luck eth2 finding your problem cant wait to hear the outcome

Edited April 12, 2014 by A1UC

[eth2]

What does a passive direct box do that a 3:2 cheater plug would not do? Are they both intended to eliminate ground loop issues?

[NOSValves]

eth2,

If you have a multimeter available test the resistance from the outer shell of the rca input jacks on the amps to the ground strap between the power supply and the amplifier unit. I'm curious if the rca cables are grounding the amps to the preamp.

[eth2]

Thanks Craig,

I do not have a meter, but I am currently using the VAC 80 (not a mono block) which has the same hum problem as the VAC 90 which is the mono block. Someone suggested that I purchase a passive direct box, but before I dump another few hundred dollars on this problem I want to make sure that the passive direct box is not just a duplication of the line conditioner I just bought (it makes no difference) or the 3:2 plugs.

[USNRET]

Did you get the chance to take the system to another house?

[eth2]

Yes, I took the VAC 80, but I did not know my friend's equipment (preamp) only had XLR outputs. My equipment has only RCA inputs/outputs So I was unable to test the amps. However, since both tube amps are acting the same way, it must be something here. I just ordered a Radial ProD2™ Stereo Direct Box, depositing yet another couple hundred dollars into the sink hole of audio bliss. Let's see...

[CECAA850]

I just ordered a Radial ProD2™ Stereo Direct Box,

I thought you determined it wasn't a ground loop?

[eth2]

That was my original question. Am I wasting money by buying these given that the 3:2 connectors have no effect?

http://www.amazon.com/gp/product/B001ESK5NO/ref=oh_details_o00_s00_i01?ie=UTF8&psc=1

Previously I tried this (and still have it).

http://www.amazon.com/gp/product/B001J1LG2U/ref=oh_details_o05_s00_i00?ie=UTF8&psc=1

Edited April 16, 2014 by eth2

[CECAA850]

Am I wasting money by buying these given that the 3:2 connectors have no effect?

I would think so but there are others posting in this thread that are much more knowledgeable than I am. Maybe these would break the ground loop on the signal side as opposed to the power side?

[babadono]

Direct boxes are usually used to take a signal DIRECTLY from an electronic musical instrument (electric guitar for instance) and feed it into a mixing console as opposed to putting a microphone on the electric guitar's amplifier and feeding it to the mixing console. I think you are adding another variable into your problem that may or may not help. BTW I hope that gizmo has Jensen Transformers in it, otherwise you are getting ripped off.

no affiliation with Jensen Transformer yada, yada,yada. Other than they are the best IMO

Edited April 17, 2014 by babadono

[babadono]

http://www.radialeng.com/prodi-development.php

Almost as good as a Jensen but not quite.

[Chris Hornbeck]

You have a ground loop. Plain and apparently not so simple. This is called a "loop" because current can travel around a completed loop, typically on the safety earth (safety ground, third wire, etc.) path. The typical path would go something like: preamp through interconnects to power amp to panel (through safety ground) to preamp (through safety ground). Real systems are more complicated, but the problem is similar. A path through the house is one turn of a poor quality but large transformer, and inductively picks up whatever stray fields it finds. Easy to fix.

First: plug all of your electronics into a single power strip. Second: disconnect any other earth grounded wires (including cable TV, etc.) Third: plug the single power strip into the wall and enjoy. There will still be a local ground loop, but it will be small enough to not matter.

All good fortune,

Chris

Edited April 17, 2014 by Chris Hornbeck

[eth2]

Thanks Chris,

I have tried this with no luck. The only thing I have not done is disconnect the lead in CATV cable at the same time as I have disconnected all other electrical devices. I did use a common outlet/power strip.

Edited April 17, 2014 by eth2

[LarryC]

I don't feel well-grounded in this, but maybe you should disconnect the CATV lead to see what happens. Maybe a decade ago, I had an awful hum which was instantly solved by inserting some "Magic" box of some kind between the antenna input and the electronics. That sounded a little like what somebody mentioned earlier. At least see what happens.

[Chris Hornbeck]

The CATV line is earth grounded (by code) before it enters your residence, usually but not always to panel. It forms a ground loop through the cable box chassis, through interconnect cables, through other electronics chassis, through their safety grounds, and back to panel and cable safety earth. In future, this is always the first thing to look at.

To solve the problem permanently, you can buy a widget that passes cable signal but blocks audio and slightly above audio band. They're commonly called "cable ground lifters", and get one that advertizes that it can pass Internet and talk-back to the cable company. (Both are lower in frequency than the cable TV stuff). It connects in the cable line (in series).

All good fortune,

Chris