How to disperse avail. amperage?

Jea48 You have been a guiding beacon in all this. Due to the absurd costs of running 110' of wire through the soffit/underground route I have decided to bite the bullet and attempt the direct route under/beside the trees and under the patio... it's going to be a lot of digging but the soffit looks far too complex to pull apart, not to mention the direct route will save $$$hundreds. I haven't measured the exact distance but it should be between 40' and 50'. As per your recom. I'll probably make it all XHHW #2 insulated copper wire all the way (No need to bother with a junction box just to save a few bucks on the 10'-15' or so that's inside) and then place the external/underground section into 1 1/4" PVC to the sub-panel location. The rest of your advice is very very helpful too (running multi outlets off of each dedicated line), I'll keep you updated. Thanks very much! Best regards and happy Lissn'n.

Hi guys, Just an update. So far my electrician has scheduled me for the middle of next week. I made some purchases today after listening to more advice from everyone and my electrician as well. GS5556: as per your rec, and my electricians (you both said the same thing) I decided to go with one step up from what you 2 said (2 poloe 60 amp main breaker) and purchased a 2 pole 70 amp instead... I did this because I've decided to go with 8x20A dedicated (bought these breakers today) as well as 3x15 amp breakers (also bought today). I bought the Square D panel which I noted above (12 spaces) and I also bought the optional ISOLATED grounding bar for it. I bought 8x Hubbell 5362 IG's and 2x5352IG's (for 2 of the 15A dedicated lines, I'll be short by 1 terminal for now (remember I have 3x15A breakers) , but this is more than I need to start. The most serious deviation from all our discussion is that because I'm only running a 70Amp main breaker (into the 125A panel) my electrician and the guys at the electric supply store told me 2G wire is way overkill and that 4G can handle 100A service so I shouldn't waste my $$$ on the 2G and just get the 4G... which, although I was hesitant not to continue with "over-overkill everything"... I decided to do the 4G. But, I didn't skimp on the quality : it's the good heavy duty burial designated cable -referred to as XLP cable (supposedly doesn't need to be PVC encapsulated) though I will OF COURSE be running it through PVC anyway. I also didn't skimp on the ground for it... while everyone told me the ground cable can be one size smaller than the main ones, I didn't do that, I simply had an identical as the other [3] 4g cable made to use as the ground.I figured I owed the system this much at least, considering I didn't go for the 2G. It looks like the 4 pcs of 4G will probably fit 1" PVC but I think I'll use the 1 1/4" instead for ease of use. I'll also run a separate 3/4" PVC for my RPG6 cable (isn't that the cable TV designation cable?) How far away in the 18" deep trench should this cable TV cable be from the main power contained PVC to ensure no interference? If the main power is 18" down can I put the TV cable about a foot or so above it? Jea48: I was looking at the grounding screw on the 5362 Hubbells and while the main hot/neutral leads will accommodate 10g cable (probably an equivalent of a 10/2 Romex). the ground screw sure looks like a lot of work for a 10G ground wire... could I get away with a 12G ground wire there or must it be 10G? What if I ran 12/2 Romex and a 12G ground? I know it's designed for that (into a 20A receptacle) but I always hear talk on these threads that 10G is worth stepping up to. Any opinions, anyone? Thanks again guys, and I'll keep you updated. Happy Lissn'n.

I also bought the optional ISOLATED grounding bar for it.

Why? An isolated ground bar will serve no purpose. I imagine the panel enclosure will be mounted to wood studs and the branch circuit wiring will be NM-B cable. (Romex is an example of NM-B).

How does your electrician plan bonding the panel enclosure to the main electrical systems equipment ground? Is he going to install two equipment grounding conductors from the main electrical panel to the sub panel? One for the isolated equipment ground bar and one for the panel enclosure?

The most serious deviation from all our discussion is that because I'm only running a 70Amp main breaker (into the 125A panel) my electrician and the guys at the electric supply store told me 2G wire is way overkill and that 4G can handle 100A service so I shouldn't waste my $$$ on the 2G and just get the 4G... which, although I was hesitant not to continue with "over-overkill everything"... I decided to do the 4G.

NEC 2005 Table 310.16
#4awg 60 C is good for 70 amps, not 100......
Because of the distance from the main electrical panel to the sub panel I would have stuck with the #2awg minimum.

my electrician and the guys at the electric supply store told me 2G wire is way overkill and that 4G can handle 100A service

The guys at the electrical supply store are not electricians.

Did you ask to see your Electrician's Electrical License?

You are not installing an electrical service. You are installing a feeder and a sub panel. NEC does allow # 4awg for a 100 amp electrical service. But in most cases the service entrance conductors are less than 25 ft.

In your case the larger feeder wire is for voltage drop due to the air conditioning load, small refrigerator, as well as the dynamic demand your audio system's Power Amp/s
may present on the feeder. You want the voltage not to fluctuate with load changes as much as possible.

I also didn't skimp on the ground for it... while everyone told me the ground cable can be one size smaller than the main ones,

I think they confused the neutral, (The Grounded Conductor), with the equipment ground, (The Grounding Conductor).

NEC 2005 Table 250.122 Minimum Size Equipment Grounding Conductors for Grounding Raceway and Equipment.

70 amp breaker - minimum #8 awg copper.

I said go with a #6 but I think for an audio system a larger wire would probably be better.

Uh oh? The term "Voltage drop" can send shivers down my spine...Assuming this 4G wire couldn't possibly be returned, as it's already cut, it sounds like I can do at least 2 things to minimize the voltage drop:
1) "Pre-cool" the room w/ the A/C before I go in to listen (which is what I normally do anyway due to the noise)as my amps are warming up (about 1/2 hour which should be plenty)
2) Forget about the small refrigerator completely (I shouldn't be promoting liquids in the room anyway!) (or, worst case, have a plastic beach cooler instead).

"...as well as the dynamic demand your audio system's Power Amp/s may present on the feeder. You want the voltage not to fluctuate with load changes as much as possible."

The overall [cable length] distance from main box to sub panel will be about 50' (twice the 25' you had mentioned)...W/ no A/C [or refrigerator running] can I feel pretty confident that I won't have a noticeable drop (if any at all) in power to my system at this distance/scenario? At this stage of the game, if I have to consider $400 of cable (I bought extra extra length to be sure not to have underestimated) a worthless stack of novice blunder...then pay an additional $4-500 for the right stuff (the 2G)...now's the time to do it. I'll bite the bullet if I have to... especially if this is fundamentally critical to the best sound my system can deliver...In the big picture of things, it's like getting stuck with a new I/C or P/C that didn't synergize with your system but simply can't be returned (or ever re-sold!) ouch!! (but I'd really rather not!)

As for the separate ground...I'll ask my electrician (who came highly recommended from a contractor friend of mine)and who claims to be fully licensed...what I will do there. The Hubbell I/G outlets can still be used anyway, yes? Even if they're simply grounded back to the sub panel's standard grounding bar?

Yes, the sub panel will be affixed to 2 sheets of 3/4" plywood attached to the wood walls (I'm using 3 sheets of 5/8 drywall on all the main walls for sound proofing purposes and I need the 2 pieces of 3/4" ply to get the cover of the panel out enough to be about even with the drywall).

Needless to say, I'm anxiously awaiting your advice.
Pensively. Thanks again.

At the beginning you mentioned installing dimmers. Dimmers are bad for RFI. I'd recommend just using lower watt bulbs and/or more light switches to turn on seperate lights for progressively more lighting. Possibly even use low voltage lighting when listening for a softer ambient feel.