|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
173.28.177.136
In Reply to: RE: EVERYTHING in life depends posted by Victor Khomenko on August 19, 2014 at 10:00:46
Like I said it depends on the design of the audio equipment. If the designer was under the impression that earth has some mystical magical power that will suck EMI/RFI noise from his equipment and the designer connects the signal ground to the chassis safety equipment ground then yes long multiple dedicated runs may cause ground loop hum problems. I have seen the same problem where said equipment is plugged into the same duplex receptacle fed from the same branch circuit. What does the manufacture suggest the user do in that case? Use ground cheaters?I have also seen ground loop hum problems where only one new dedicated branch circuit is installed and the user uses an existing convenience outlet receptacle circuit to power other equipment that is connected together by ICs. This can definitely cause ground loop hum problems.
IF the run is long and the connected load is small make sure the wire is the same gauge and approx the same length. Also as in my case I installed #10 ga wire. Over kill? Maybe but my system is dead quiet.
I would rather have multiple dedicated audio branch circuits of say 40' to 50' long than multiple dedicated audio branch circuits of 10' or less. Not much power supply decoupling going on with 10' or less long branch circuits.
Jim
Edits: 08/19/14Follow Ups:
Well, you are not correct. As I mentioned before, the equalizing currents, flowing through your interconnects, will be the main source of ground loops. Therefore your goal is to keep the ground potentials between various pieces as close as possible.
It is true that the effect will depend on how the particular pieces of equipment are designed, but the bottom line is - you don't intentionally build a trouble prone system and then hope it will work, you from that perspective, your power amp and your preamp both plugged into the same circuit is the safest solution.
If you put your power amp and your preamp on separate long lines, there will appear a sizable voltage difference between their chassis and neutrals. The best way to avoid it is to install the sub-panel, as I mentioned, and keep the power lines between the components as short as possible.
Nothing will ever guarantee a 100% noise free environment, as some equipment may not be properly designed, but this approach will be the safest.
"Well, you are not correct. As I mentioned before, the equalizing currents, flowing through your interconnects, will be the main source of ground loops. Therefore your goal is to keep the ground potentials between various pieces as close as possible."
IF the audio equipment uses double insulated power wiring there is no equipment ground used in the equipment and therefore any difference of potential between safety equipment grounding conductors of multiple branch circuits would not be involved.
IF audio equipment that uses an equipment safety ground does not have its signal ground connected to the chassis with the safety equipment ground then there would be no current path provided through the ICs from one grounded piece of equipment to another grounded piece equipment where its signal ground is also not connected to the chassis.
Beats me why any designer/manufacture of audio equipment connects the signal ground to the safety equipment ground. Again the earth does not possess some magical mystical power that sucks EMI/RFI from audio equipment.
"If you put your power amp and your preamp on separate long lines, there will appear a sizable voltage difference between their chassis and neutrals. The best way to avoid it is to install the sub-panel, as I mentioned, and keep the power lines between the components as short as possible."
First, I have my power amp and preamp connected to the same 20 amp dedicated branch circuit. Digital equipment is plugged into the other 20 amp dedicated circuit. But in my case with my equipment it wouldn't matter.
"If you put your power amp and your preamp on separate long lines, there will appear a sizable voltage difference between their chassis and neutrals."
Please explain further.... "there will appear a sizable voltage difference between their chassis and neutrals."
Grated if the user was using a big poweramp there could be a VD, (voltage drop) at the end of the branch across the connected load.
If the amp is built for the home consumer good chance it will be fitted with a 15 amp plug. Per NEMA and UL standards the FLA draw of the equipment can not exceed 12 amps. Thats a lot of AC power 120V X 12 amps = 1440 watts. Even at a connected load of 12 amps FLA on a branch circuit using #10 wire that is 70' or 80' I doubt there would be any measurable VD. But even if there were please explain how a slight difference of potential from one neutral of a branch circuit to the neutral of another branch circuit could cause a ground loop hum. Remember you are talking about the neutral, the current carrying conductor (The Grounded Conductor) and not the safety (Equipment Grounding Conductor).
Getting back to reality I would bet most guys here,.... with all the load of their audio equipment added together does not exceed 10 amps.
Jim
Simply disconnect the equipment from each other and then measure the AC voltages between their chassis and between their signal grounds, in many cases you will see significant voltages present. Sometimes because the signal ground is, in some way, connected to the safety ground, sometimes due to induced potential, but it is often there.
Putting in the sub-panel pretty much eliminates this.
Simply disconnect the equipment from each other and then measure the AC voltages between their chassis and between their signal grounds, in many cases you will see significant voltages present. Sometimes because the signal ground is, in some way, connected to the safety ground, sometimes due to induced potential, but it is often there.
Agree.
But it should be said the difference in potentials is not always caused by the branch circuit wiring. Sometimes the potentials are caused because the primary winding of the power transformer of a piece of audio equipment was not checked for the proper AC polarity orientation when it was installed and wired into the circuit of the equipment. Due to coupling capacitance of the primary to the secondary of the transformer there is a very good chance there will be a difference of AC potential, voltage, measured from the signal ground of the reversed AC polarity of a piece of equipment to one that has its AC polarity orientation correct.
Sometimes the proper AC polarity orientation is caused from an improperly wired aftermarket power cord where the hot and neutral conductors are reversed at either the plug or the IEC female connector. Usually the reversal is at the IEC female connector.
Also an improperly wired AC power receptacle can have reversed AC polarity.Wire and wiring methods used for audio branch circuits.
Quote:
The “Conduit Transformer”
• This finally explains what drives 99% of all ground loops!
• Load current in line and neutral produces opposing magnetic fields
since instantaneous current flow is in opposite directions
• Imperfect cancellation magnetically induces voltage over the
length of the nearby safety ground conductor
• Strongly affected by geometry and proximity of wires
• Highest voltages with randomly positioned wires in conduit
• Lower voltages with uniform geometry of Romex®
• Voltage is directly proportional to load current, wire length, and
rate of change in current or ΔI/Δt
• Mechanism favors high-frequency harmonics of 60 Hz
• For constant current in L and N, induced voltage rises at 6 dB/octave
The “Conduit Transformer”
Wires randomly positioned in conduit
produce the worst possible results!Bill Whitlock, 9/4/2012 Overview of Audio System Grounding & Interfacing
Using the proper wiring materials and method of installation is important. Use NM cable (Romex is a trade name NM cable) or MC Cable with an outer aluminum armor jacket. This is a must for long branch circuit runs.
If using NM cable sharp bends should be avoided. Do not coil up any excess power cabling.
Putting in the sub-panel pretty much eliminates this.
Victor
A sub panel can be beneficial if the user has a place out of sight of the living quarters. There in a mechanical room. If installed in the audio listening room and the user later decides to put his home up for sale how will the appearance of the electrical panel appeal to a potential buyer?
And then there is the added cost of the electrical panel, feeder wiring materials, installation labor costs. Especially if the user only wants or needs 2 dedicated circuits installed.
Edits: 08/20/14 08/20/14 08/20/14 08/22/14
Just curious,if the hot and neutral are reversed would not the chassis on the component have voltage going through it and be a hazard?
Just curious,if the hot and neutral are reversed would not the chassis on the component have voltage going through it and be a hazard?
The neutral conductor is a current carrying conductor and is never connected to the metal chassis, case, or frame of a piece of equipment.The main service neutral conductor is connected to earth and bonded to the service equipment enclosure. The neutral shall not be connected to earth at any point thereafter per NEC Code.
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
http://www.gcaudio.com/resources/howtos/acpolarity.html
Edits: 08/25/14
On the advice of a few gurus here and elsewhere this is what I did installing a dedicated circuit.
Using 10ga wiring make a twisted pair of the needed length. Take another 10ga wire for the ground and twist it in the other direction with half the twists per foot of the first pair. I'm out in the woods with no rf problems so I used non-metallic conduit. Some commenters thought a metal conduit might be slightly less dynamic.
Using 10ga wiring make a twisted pair of the needed length. Take another 10ga wire for the ground and twist it in the other direction with half the twists per foot of the first pair.
Yes I have heard that works quite well. Bill Whitlock shows test results where the hot and neutral conductors are twisted together. (See page 35 of PDF Link below. (The twisted together hot and neutral conductors gave the best results.)I should also mention Sean a member of Agon and AA was recommending twisting the hot and neutral conductors together in posts back in the early 2000s.
As for meeting NEC not sure it would. Not sure if the wires could be pre twisted together before installing in a conduit. The pre twisting together of building wire to then be installed in a conduit would have to be approved by the wire manufacture and then Listed by UL or a recognized testing laboratory. It would also need to be look at as to how it affects conduit fill.
Is it safe to do so for powering audio equipment? Jmo I would not find a problem with it. Connected loads are usually quite low so over heating of conductor insulation due to current flow through the conductors would not be an issue.
Jim
Edits: 08/25/14
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: