Wiring for media room

[klettermann]

My media room is proceeding apace. Next step is finalizing electrical layout and wiring it up. The idea is 2 new 20A circuits. One will be dedicated to big, high current power amp. Someplace I read or heard that armored BX cable is (or might possibly be?) better than romex for audio uses. You know, better EMF/magnetic/cosmic ray shielding. I'm not much of a believer in that stuff but, OTOH, it can't hurt. But it's more $$$. Or am I truly burning $$$? I figure on using hospital plugs on principal cause why not? I got 1 chance at this. Any thoughts on all this? Thanks and cheers,

 

[DonH56]

I personally would not use armored cable due to cost (for conduit and installation) and very limited benefit. You have all sorts of unshielded wiring and noise sources around the house, including the equipment in the room, and your equipment should reject that noise. Going to 20 A runs is a good idea as it will also get you 12 AWG Romex instead of 14 AWG (at least in our area, may depend upon local codes). I would suggest, in addition to the main 20 A drops for your equipment (I assume at the front of the room), you might run another 20 A drop to the back of the room for subs and such (if and when), and a standard 15 A drop for other outlets around the room. Our electrician also wired the top outlet in a couple of duplex sets to a switch so I could plug in floor and table lamps that were switched off near the door. I do not have overhead or in-wall lights (one sconce) because the walls and ceiling float and I wanted to minimize holes and potential for rattles later.

Hospital plugs usually offer better retention for modest cost but more a feel-good thing IMO than actual benefit unless you are plugging and unplugging stuff a lot.

In addition to isolating the walls and ceiling using Kinetics Noise Control IsoMax clips, and copious Rockwool in the walls, I added a mini-split HVAC unit for the room so there are no ducts to the rest of the house, That minimizes noise/sound into and out of the room, to the extent that at full-blast you cannot tell elsewhere in the house, barely even in my boy's room on the other side of the wall (basement room so floor is concrete). Code required an external air vent (inlet) and exhaust fan (outlet) which has been helpful in preventing the room from getting too stuffy. The door is a large (36", I think) heavy (solid) exterior door with full seals and threshold, again to reduce noise to/from the room.

FWIWFM - Don

 

[Speedskater]

Real SouthWire brand Romex® is great. With generic Non- Metallic-B (NM-B) romex, you never know what you are getting.
Most hi-fi systems only need one 20 Amp circuit.
Do your amps have 20 Amp AC plugs?

For large home theater systems. Rather than two 20 Amp circuits from the main breaker box.
Run one 40 or 60 Amp feeder from the main breaker box to a central point in the A/V room and install a 6 breaker box at that point.

 

[JeffS7444]

While the wiring is still visible, I'd periodically inspect to ensure that contractors aren't taking shortcuts! While doing a site inspection at a former employer's facility under construction, I discovered that critical server room circuits had been shared with outlets in a hallway where cleaners might be expected to plug in vacuum cleaners! Wiring diagram clearly showed they were not to do that, but someone simply ignored it. Similarly, if you desire a 20 A circuit solely for amplifiers, make sure it's really only feeding the desired receptacles.

Outlets can be replaced at any time by homeowner. Last time I checked, I think Hubbel hospital grade was something like $8 versus $1.50 for ordinary duplex receptacles. If hospital-grade is made of plastics which are less likely to crack, it might be worth the extra $.

Think that armored cables are intended for situations where there is a risk of physical damage to the wiring, not for shielding.

Oh, and ensure that GFCIs (Ground Fault Circuit Interrupters) aren't used except as required by code. Yes, same contractors installed a bunch of them in a lab processing area which had no plumbing, and certain kinds of electrical loads would periodically cause them to trip.

Take photos, so if you need to drill holes into the wall in the future, you know where not to drill.

How's the HVAC situation? I got stories about that too.

 

[Kal Rubinson]

Think that armored cables are intended for situations where there is a risk of physical damage to the wiring, not for shielding.

They are required by law in NYC.

 

[DVDdoug]

Armored cable is no better electrically. If you are building/re-building I don't know if it's cheaper that regular conduit (if want or need the physical protection). Your electrician can advise you.

But heavier gauge (a lower gauge-number) will result in less voltage drop. Not really an issue... but the voltage drop in a cable is related to the resistance (length & gauge) and current. With higher current you get more drop. Or if you've got two more circuits with their own wiring, each set of wires has less current so less voltage drop.

There are electrical codes for amperage & distance but I assume you can go heavier gauge.

I believe the only thing special about hospital outlets is there is a spec for how hard they are to un-plug. So plugs don't get accidently pulled-out as easily. (Your electrician can tell you that too.) They MIGHT not hold any tighter than another outlet, but there's a spec-requirement. But if I trip-over a cord, it's probably better that it comes-out that I fall down!

One will be dedicated to big, high current power amp.

It might be better to separate the audio from everything else. That gives you SOME noise isolation in case something else is putting noise on the power lines. (It doesn't make a big difference since everything is connected together back at the breaker box.)

What's the actual amperage rating on the amplifiers? (It's usually labeled on the back near the power connection.) As you may know, class D amplifiers are nearly 100% efficient (at high power) so they don't suck much more energy out of the wall than is going to the speakers. Class-A amplifiers waste a stupid amount of energy, even when idle.

And if you don't know this... There is a "power transformation" so you can pump more current into the speakers than comes-out of the wall (at lower than wall-voltage).

 

[DonH56]

They are required by law in NYC.

Vexing. Due to fire codes?

 

[Kal Rubinson]

Vexing. Due to fire codes?

I suppose that was the original reason. It remains, probably, due to the insistence of trade unions.

 

[pseudoid]

Hi @DonH56,
In his youtube video, Ken Fritz stated that he went up to 220Vac for his amps... I thought it a clever work-around but not sure if relevant.

Besides the audio wiring; what are your plans (if any) for your network wiring... and possibly your video stuff?

 

[Speedskater]

:

I suppose that was the original reason. It remains, probably, due to the insistence of trade unions.

No, electricians hate GFCI and now AFCI breakers. They keep tripping at random times resulting in call-backs.
It's the manufactures that pushed them thru NEC. They are high profit items.
Some communities don't require them on upgrading older homes wiring. Because they add so much to the total cost, the home owner won't do any upgrade.

 

[DonH56]

Hi @DonH56,
In his youtube video, Ken Fritz stated that he went up to 220Vac for his amps... I thought it a clever work-around but not sure if relevant.

It's a good way to cut amperage draw, and thus IR (voltage) drop, in half, but that means another line run and depends on what amps you have. I decided to just get extra 20-A circuits. I have at times had everything on one 20-A circuit and never blew a breaker though I've not measured the power draw.

Besides the audio wiring; what are your plans (if any) for your network wiring... and possibly your video stuff?

I think this is for @klettermann ? Which reminds me, where in the Rocky Mountains (PM me if want to keep private, or just say MYOB)?

 

[DonH56]

Random thoughts:

No, electricians hate GFCI and now AFCI breakers. They keep tripping at random times resulting in call-backs.
It's the manufactures that pushed them thru NEC. They are high profit items.
Some communities don't require them on upgrading older homes wiring. Because they add so much to the total cost, the home owner won't do any upgrade.

AFCI breakers were newly required when we finished our basement. The treadmill, in a different room and on a separate circuit, would trip the AFCI, put the lights out, and plunge my son into darkness. Ditto if I ran the vacuum cleaner on most any circuit in the basement (which had its own subpanel). After the third time it was replaced, I asked and the electrician left me an older non-AFCI breaker for the light circuit, which he could not install but I could on my own if I wished.

 

[terryforsythe]

My media room is proceeding apace. Next step is finalizing electrical layout and wiring it up. The idea is 2 new 20A circuits. One will be dedicated to big, high current power amp. Someplace I read or heard that armored BX cable is (or might possibly be?) better than romex for audio uses. You know, better EMF/magnetic/cosmic ray shielding. I'm not much of a believer in that stuff but, OTOH, it can't hurt. But it's more $$$. Or am I truly burning $$$? I figure on using hospital plugs on principal cause why not? I got 1 chance at this. Any thoughts on all this? Thanks and cheers,

I ran two dedicated 20A circuits for my stereo system. I just used Romex.

If you have anything emitting electromagnetic interference (EMI) immediately near where the wires will be ran, you might want to run metal conduit and run the wires inside the conduit, or just use armored BX cable.

If you are worried about EMI sources outside your home, chances are they will couple onto your power lines before your breaker box, and so it will be on wiring regardless of whether you use armored BX cable. So, you might as well just use Romex. Nonetheless, well designed power supplies have filters to deal with EMI.

 

[Speedskater]

Random thoughts:

a] Hospital grade receptacles ~ the main differences between hospital grade and top shelf receptacles are documentation and plating to resist harsh cleaning compounds. But it's often easier to find hospital grade than top shelf in the store.

b] 20 & 15 Amp receptacles ~ the only difference between 15 Amp and 20 Amp at a given quality level is in the plastic parts. All the internal metal parts are rated at 20 Amps in either case.

c] Voltage drop ~ It all about source impedance. It's a Series Circuit. It starts at that big power company transformer and ends at the amplifier's AC input. A larger conductor on a long segment of the run will help lower the source impedance. A larger 6 foot cord won't do much.

 

[pseudoid]

Random thoughts:

If you are going to start that train of thought, then, please allow me to add one more:
d] Earth-ground [and not just 3rd-wire "AC protective"] << How good is it?

• Especially since @DonH56 indicated that the house has been around for a few decades?

 

[DonH56]

Random thoughts:

a] Hospital grade receptacles ~ the main differences between hospital grade and top shelf receptacles are documentation and plating to resist harsh cleaning compounds. But it's often easier to find hospital grade than top shelf in the store.

b] 20 & 15 Amp receptacles ~ the only difference between 15 Amp and 20 Amp at a given quality level is in the plastic parts. All the internal metal parts are rated at 20 Amps in either case.

c] Voltage drop ~ It all about source impedance. It's a Series Circuit. It starts at that big power company transformer and ends at the amplifier's AC input. A larger conductor on a long segment of the run will help lower the source impedance. A larger 6 foot cord won't do much.

One comment: 20 A receptacles are compatible with 15-A plugs, but have an extra horizontal contact for 20-A plugs (which are not compatible with 15-A receptacles).

 

[Ron Texas]

This sounds awfully complicated. I guess it's the result of excessive regulation pushed by special interest groups.

 

[DonH56]

If you are going to start that train of thought, then, please allow me to add one more:
d] Earth-ground [and not just 3rd-wire "AC protective"] << How good is it?

• Especially since @DonH56 indicated that the house has been around for a few decades?

I have no idea how old the OP's house is. I am not sure where I said decades (literally -- I am sure I said it, just not sure the context). I have been doing this stuff for about 50 years, but our house is "only" about 30, and the basement media room was finished was roughly 12-15 years ago (have to ask my wife for the exact date ).

The third wire in the USA is a safety ground and is tied to the neutral wire at the electrical service box. It provides a safety path for leakage current and ground point for three-wire chassis shields and equipment, and some of the special breakers discussed here. If by "earth ground" you mean a ground rod, that is usually provided by the electric company if required. In many places adding your own ground is against code as it can create an uncontrolled and unknown current path. A lot (perhaps most?) of today's components do not even have a safety ground connection (they use two-wire power cables; I have also seen a number of components that have three-wire cables but the safety ground is open inside).

If you are having electrical work done, it's not a bad idea to ask the electrician to check the tightness of all the connections in your service while he's there.

 

[GXAlan]

This sounds awfully complicated. I guess it's the result of excessive regulation pushed by special interest groups.

I actually think that electrical safety is something that isn’t excessive. The problem isn’t GFCI or AFCI but that a lot of GFCI/AFCI products are made to a very low spec.

I had a lot of problems with a GFCI plug in my garage and swapped a Made in China Legrand for a Made in Mexico Leviton. I don’t know if country of manufacture makes a difference but there were clearly physical build quality differences and the replacement GFCI has worked perfectly.

If you think about safety like UL, CSA, CE, you probably can get away with a poorly made product that trips more often than it should because it would still be safe.

https://www.nema.org/docs/default-source/products-document-library/arc-fault-circuit-interrupters-using-advanced-technology-to-reduce-electrical-fires-se-1512.pdf?sfvrsn=8ec37ebc_3

 

[klettermann]

Thanks for the comments, very helpful. My electrician is excellent and has done lot of work on the house in the past, so I won't have problems with the GFCI stuff or lazy shortcuts or any of that. Having a dedicated breaker box is a nice idea. Amp is a ML No. 332 driving big Magnepans @ 4 ohms - not completely crazy, but still a relatively high current setup. A lighting circuit is already in place so I guess I'll go with the 2 20A circuits, one for the amp and the other for other electronics, another 15A for other outlets (no huge subs are in the future) and maybe put the lights on the same box. I got isolation putty for the outlets. As for hospital outlets, my theory is that the tighter contact has to be a good thing and the case material (nylon) is certainly more robust.

Apart from that, isolated walls, rockwool etc are all part of the plan. The space has a dedicated duct going straight to the HVAC unit and no other pesky ducts to worry about, so minimal ducting, ventilation or sound transmission issues. Egress is though 2 doors separated by a hallway. If that proves to be too loud then I'll soundproof the doors.
[sidebar: I have a powder room on the side of a large kitchen/'great room." The arrangement and construction was totally oblivious to noise issues. It was remodeled with insulation, better sealing of everything and a completely sealed door. Now, standing right in front of the door, the toilette is inaudible. The Wife loves it. Nice!] Cheers,