New listening room electrical design

The new system proposed outline:
New dedicated subpanel, exclusively for the audio components (main located in the garage, adjacent to the new room).

JMHO, if the subpanel will be somewhat close to the audio equipment’s branch circuit wall receptacles (15ft or less) imo, that kind of defeats the purpose of multiple dedicated branch circuits for the purpose of decoupling the power supplies of audio equipment from one another. Especially Digital from analog.

Imo, the amount decoupling is largely due the length of the branch circuit wiring impedance of the branch circuit wiring used, especially NM-B cable (Romex is a trade name of NM-B), or MC cable. (Both use THHN insulated copper conductors.)

Of course the other reason for multiple dedicated branch circuits is for fluctuating VD, Voltage Drop, that may be placed on the branch circuit from a big power amp/s playing a high dynamic music source. You don’t want the voltage fluctuating that could/would have an impact on the power amp’s power supply or power supplies of other audio equipment fed from the same branch circuit. Short runs of 20ft or less of #12awg would more than likely not be a problem. When in doubt using #10awg wire eliminates any VD fluctuations problems as the power supply of an amp draws quick gulps of current to recharge the caps in the power supply.

As always YMMV.

However, not being an electrician, I’m having a hard time to picture having one or two lines with 6-8 outlets located in different locations?

First, my intent of my previous post was not to discourage you from installing multiple dedicated circuits.

As for feeding more than one receptacle outlet from the same branch circuit it is done all the time. The feed in and feed out wires in the outlet box are jointed together and pigtailed out for connection of the duplex receptacle. As for the wire connector used to make up the joints, connections, a spring type connector should be used. Example, Scotchlok brand made by 3M or equal as used in commercial/industrial facilities. Stab in connectors used in residential dwelling units are junk!, imo.

https://www.egr.msu.edu/eceshop/Parts_Inventory/datasheets/insulated%20electrical%20spring%20wire%20...

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I was actually thinking of 8/2 just for the amps.

#8awg? Must be some really big powerful amps. #10 is more than big enough. VD will not be a problem for your short branch circuit runs. I would be willing to bet the plug on the power cord feeding the amps is only a 15 amp plug.

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Since we are on this topic, what specific brand and model of the subpanel would you recommend?

First, copper bus only. Stay away from a panel with Aluminum bus. The problem isn’t that the bus is aluminum it has more to do with the bus breaker tie connection made to the branch circuit breaker bus tie connector connection.

I personally like the Square D QO series. It has copper bus. Stay away from the Square D Homeline series. It has aluminum bus and I don’t care for the branch circuit breakers.

How big of a feeder was you thinking about to feed the sub panel?

For house resale I would wire the panel 120/240V. Though you will/should still have all your audio equipment that is connected together by wire ICs all fed from the same Line, Leg. All from Line 1 or all from Line 2. Not from both.

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You need to find a good licensed electrical contractor/electrician to work with you. He will know what is required for local electrical code in your area.

Worth noting if an electrical permit is pulled there is a very good chance the branch circuit breakers in the new sub panel will have to be AFCI (ARC Fault Circuit Interrupter) type. Maximum breaker size for a 20 amp branch circuit is 20 amp, no matter if the wire is #10awg.

The electrician more than likely will have to install tamper resistant duplex receptacles for the final electrical inspection and then change them out to your audio grade duplex receptacles, after the electrical inspector signs off on the job. Ask him up front if local code for your city requires them. If yes then ask him if he will change them out after the final inspection. He may say no. He may not have any problem with changing them out providing you say you did it and not him.

Beats me why the manufactures of the audio grade receptacles are not making them tamper resistant for a residential dwelling unit application.

one more question- how would you suggest to install 2, or 3 duplexes on the same line in the same location?

The wiring method depends on the construction of the house. Without knowing the construction of the house there is no easy answer to your question. The electrician you hire will look over the construction of the house and will determine the options of the wiring methods he will have. He then should explain the options to you.

Things to consider:

Wood stick framing? Other?

Basement? Unfinished or finished ceiling in area below the audio room?

Foundation crawl space?

House/audio room built on a concrete slab?

Above ceiling attic accessible crawl space? Other?

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i don’t know the feeder size, bu the one I have in my current home is pretty big
you can see it in my system pics
what size do you think I’d need?

Well if you are going to spend the money to have a sub panel installed the bare minimum size in my opinion would 70 amp. Wire size #4 copper. Or bump up to #3 which is good for 85 amps.

What is the aprox total length of the feeder? Include up down and all around in the calculation. Does the garage have an accessible attic crawl space to install the feeder? If so you might want to consider NM-B sheathed cable or MC instead of conduit with loose random conductors pulled inside. Depends on the total run, length, of the conduit and installed feeder conductors.

http://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

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And what is your opinion on twisting the wires?

Twisting the wires? As in wires, conductors, that are pulled in an empty conduit? Not sure that meets NEC (National Electrical Code). Note: Dedicated branch circuits should never share the same conduit or raceway with other branch circuits. That includes multi conductor cables.

For the branch circuit wiring from the sub panel to the wall receptacle outlet boxes I would use NM-B cable, Romex. (If local code permits. And or the wiring method that must be used will meet local code for NM-B cable.) If the wiring must be in conduit ask the electrician if aluminum armor MC cable, 2 wire with ground, meets local code. Note: MC, not AC cable.

(MC comes in both solid core and strand copper conductors. Specify solid core only. Beings you will be using #10 wire the electrician will try to talk you into using stranded. He will tell you they are both rated for 30 amps. Stand your ground, Solid core only.

Example of 10-2 with ground MC cable with aluminum armor.

http://www.lowes.com/pd/250-ft-10-2-Solid-Aluminum-MC-Cable/3637694

The audio room is in the basement?

Garage floor and audio room floor are approximately on the same elevation?

Common garage wall is unfinished concrete?

All walls and ceiling of the audio room are finished drywall?

Three walls of the audio room are concrete furred out with studs? Are you sure they are studs and not 3/4" furring strips? If studs are they 2" x 4 1/2" nominal studs or possibly 2"x 2" nominal? (1 1/2" x 1 1/2")

If they are indeed 2x4s do you know if possibly they were spaced out from the concrete walls by at least 1" or 2"? Hopefully so. You can check this by removing a wall plate from a communication wall outlet, if there is one in the room. Otherwise remove the cover plate from a duplex receptacle. Take a metal close hanger and straighten it out or cut out/off the long part of the hanger to use as a depth probe. If you are lucky the communication box may be an open back wall communication bracket. Then you can physically look inside. If not make a hole against the side of wall rough in box, side opposite the stud side the box is supported to. Push the wire through the hole made in the drywall to the concrete wall behind. Mark the front of the wire probe. Measure the length.

David Pritchard said:

The Synergistic Research Black outlet is a TR (tamper resistant) outlet.
I do think it does a fabulous job of improving the system’s sound.

Thanks for the info.

Just going from memory I believe Synergistic Research has Leviton build their receptacles. Adding the TR face plate is easy to do, for a price, and thereby makes the duplex receptacle code compliant for use in a residential dwelling.

Just a guess others will follow. They are probably trying to sell off their existing inventory first. That still doesn't make it right, code compliant, though.

maril555,

How about an up date. What did you find out on the wall framing construction of the audio room?

my question is, how you gonna do that, if all 3 are in the same jacket, as in 10/2 Romex?

Whitlock is talking about single conductors pulled in a conduct or installed is a raceway. As I said in an earlier post twisting the hot and neutral wires together before installing them in a conduit may not meet code. Are you planning on installing conduit?

Whitlock showed the second best choice being 2 wire with ground MC armor cable followed by Romex. You can slightly twist Romex, but to much, to tight, will change the geometry of the lay of the equipment grounding conductor in relation, between, the hot and neutral conductors. Just a slight spiral twist in the entire length of the cable. Slight.....

FWIW I have to runs of 10-2 with ground NM-B, Romex, that are about 75ft each and my 2 channel system is dead quiet. Preamp and amp are tubes.

It is important to keep the individual dedicated branch circuits separated from one another as soon as possible, within reason, after they leave the electrical panel. You do not want them running parallel next to one another.