New dedicated lines have high noise floor.


I just installed two dedicated lines for my system.  Each is on its own 20a circuit breaker.  I used 10 gauge hospital grade MC cable (exact same length) and Cardas 4181 duplex outlets.  I was expecting a quieter noise floor and better sound.  I have a 3x to 4x increase in the noise floor compared with a regular outlet nearby.  One of the circuits has a "crackling" sound.  For the best results, I need to put my amp and source equipment on a single outlet.  If I use both the sound gets worse.  Any ideas?  I need to have my electricians come back, but would like to have some audiophile wisdom for support.
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pg62 put all your source equipment on one line via one outlet strip and put your amp on the other. Float the ground to your amps using cheaters.
Let's see how that works.
@ pg62

Why did you use hospital grade MC cable?
For audio 10-2 with ground would have been better.


Problem with hospital grade MC cable there are 4 wires. one Hot, one neutral, and two equipment grounding conductors. The geometry of the way the 2 equipment grounding conductors are installed in relationship to the current carrying hot and neutral conductor makes it more possible that a voltage is induced onto the equipment grounding conductors.

Did the electrician terminate both circuits on circuit breakers on the same Line, leg, in the electrical panel? Both on Line 1 or both on Line 2?

One of the circuits has a "crackling" sound.
That sounds like a loose connection. Could be a faulty circuit breaker, or a poor connection between the breaker to the connecting bus tie in the electrical panel.What type/manufacturer panel is it?
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You should not have "a crackling sound" coming from your AC line and if you do, it suggests something faulty in the installation, such as a loose connection. I’d have your electrician check all of his work.

Did you take out a construction permit for this work? In many municipalities in the U.S. such a permit would be required. If so, your code inspector may be helpful in identifying the issue.
The crackling is a real issue.  Please have it checked, you may have arcing somewhere.

The other issue, is one I have warned about before. Having too good of a connection to the panel means you may get closer to any noise from outside.

A better solution may be to run 240 to your room, and then use a step down balanced transformer, like from Equitech, to feed your gear. This is fairly cheap to do, as you've already run the wiring. Just need a new, dual pole breaker and appropriate outlet.
Before you call your electriticians, there is something for you to try.

Turn off every other breaker in the home. If the noise persists, it's on the line, or from the outside. If it all goes away, it's coming from elsewhere in the home.

If your breaker box is old, you may also want to ask about arc detecting breakers.

Best,
E

@ pg62

AC Power Wiring Types (cont’d) Metal Clad (MC)is manufactured in both steel and aluminum with twisted conductors that help reduce AC magnetic fields. Although the steel jacket helps reduce AC magnetic fields, the twisting of conductors has the greatest effect on reducing these fields. Another benefit is the constant symmetry of the phase conductors with respect to the grounding conductor which greatly reduces voltage induction on the grounding wire. (NEC article:330)


Two conductor plus 1 ground MC (Metal Clad)is a good choice for Non-Isolated Ground A/V systems. MC cable contains a safety grounding conductor (wire). The three conductors in the MC cable (Line, Neutral and Ground) are uniformly twisted, reducing both induced voltages on the ground wire and radiated AC magnetic fields. The NEC article 250.118 (10)a prohibits the use of this cable for isolated ground circuits because the metal jacket is not considered a grounding conductor, and it is not rated for fault current.


Two Conductor plus 2 ground MC (Metal Clad)may be used in an Isolated Ground installation, because the cable contains two grounding conductors (one for safety ground and one for isolated ground). The conductors are twisted, but the average proximity of the hot conductor and the neutral conductor with respect to the isolated grounding conductor is not equal. Under load, this will induce a voltage along the length of the isolated ground wire, partially defeating the intent of isolation (see Ground Voltage Induction section of this paper).

~


Single-Phase 120/240V electrical service is most commonly found in residences and smaller commercial buildings, and is commonly used to feed AV equipment. One key advantage that single phase has over three phase is that while harmonic currents are still present, only even order harmonics can add in the shared neutral, and they are uncommon, since the waveform would be asymmetrical. In addition, use of single-phase 120/240V can result in at least a 6dB reduction in noise floor as compared to three phase if the capacitances of the connected equipment are relatively well balanced. Furthermore, if a signal cable is connecting two pieces of ungrounded equipment powered from opposite phases, the leakage current flowing in it will increase (causing more noise) as compared to powering the equipment from the same phase.

Integrating Electronic Equipment and Power into ... - Middle Atlantic


Read pages 31 thru 35
https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

Jim
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@jea48. 
Thats an excellent bit of information for all our Audiogon friends. Thank very much. Pete
Great feedback everyone.  Much appreciated.  I took the hospital grade MC cable recommendation from my electrician.  Jim, I think I need to read that passage several more times to get the gist of it,  I have a call into my electrician and will share the wisdom found here.  Thank you all.  I'll let you know how this turns out.  Pete 
Jea48, the 2 circuits are parallel on the panel.  Is that an issue?  The panel is a relatively new (9-years) 200 amp panel.  It is full with no additional slots.  I've got another 150 amp panel next to it which is also full.
+2 jea48 (as usual)
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Sometimes audio components sound far better on the same star grounding scheme. So by splitting your system across two separate lines back to the breaker box, some type of ground loop issue is occurring.

Have you tried feeding everything using the one power point, and does that make any difference?

Re: Hospital grade wiring, I would ditch it. Hospital grade does not mean good. For example hospital grade duplexes means a duplex that can withstand constant water splashing from cleaners washing the hospital rooms each day. In order to not corrode from the water, the metal in a hospital duplex must be all nickel plated, which is the worst sounding plating for audio systems.

This is a good example of how 'hospital grade' is good for its stated application, but awful for high end audio.