I worked in computer networking for a Federal Government Agency.  I'm now retired.  After much investigation and testing the agency settled on Isolated Ground wiring and Hubbell IG5262 (orange color) AC receptacles.  Isolated grounds require a separate, 3rd wire, that goes directly to the ground connection in the main circuit breaker panel directly to the orange AC receptacle.  This eliminates potential grounding problems using conduit or whatever.  This minimized (I won't say eliminated) AC power line problems and grounding, which also reduced noise on the power line. UPS systems were used on the office's file server and communications modem, and high $$ surge protectors on all the workstations (PC's) and peripherals.
 
If I were building/wiring a recording studio the Isolated Ground wiring/receptacles would be all I would use.

In a properly and solidly grounded electrical system, you should not have problems with more than one circuit supplying the power to the studio. You can even have circuits fed with both phases of the panel and have a studio that runs whisper quiet with no hum. Grounding is the secret. Proper grounding.
 
If you are planning and building a studio, you can ask the electrician doing the wiring to be sure that all the outlets that are in the studio area are ALL on the same phase from the panel. That eliminates one potential cause of noise.
 
In an existing building or house......If the studio gear has hum, and the wiring appears to be in good condition..... everything sized correctly, no reversed polarity wiring, no missing or broken ground conductor between the panel to the outlet.... one should then have a licensed electrician investigate the grounding of the service coming into the building.  A loose or missing ground at that location will cause issues. More than one time, while investigating an electrical issue in a customer's home or business I found grounding issues to be at the root of the problem. The ground rod in several cases had rusted and was only making a weak connection to ground. In another, the clamp was rusted and the copper ground wire was not connected solidly, and several were not connected at all to the ground wire. This would indeed induce a voltage and create hum and other issues in a studio which is sensitive to noise on the power lines.
 
For studios in most homes, the wiring in the USA is romex. 3 wires, in an insulated jacket with a ground. plastic boxes keep the recpt yoke isolated from any conduit which is generally not used in residential construction. Not around here anyway. So if hum is a problem, there are many things that might cause it and all should be investigated one at a time until the problem is located and repaired properly.
 
And don't forget that a bad or cheap unshielded mic or connecting cord in the gear rack can also be the culprit.

A point to keep in mind, we tend to think about maximum capability of a circuit while the safety guidelines are more concerned with providing a trip point or circuit break at a low enough level that it actually saves a life.
 
In other words, a small appliance plugged in to a circuit that has a 50amp breaker may kill you with 15 amps because the breaker never switched to safe when a smaller breaker would have.
 
I think that when you are accustomed to stacking a bunch of gear on circuit that sometimes you can forget what the breakers are for.
 
best regards,
mike

fireberd
I worked in computer networking for a Federal Government Agency.  I'm now retired.  After much investigation and testing the agency settled on Isolated Ground wiring and Hubbell IG5262 (orange color) AC receptacles.  Isolated grounds require a separate, 3rd wire, that goes directly to the ground connection in the main circuit breaker panel directly to the orange AC receptacle. 

I've done a lot of those esp. in the '80's. Then 200% neutrals became all the rage in the '90's. I settled on the orange IG receptacles in my space. The bottom line: If your power company doesn't supply you with clean power, If you share a transformer with your neighbors or you have loads that cause harmonic distortion ( i.e. flour. lights ) in your building you will have noise unless you do something to clean it up. You can use an isolation transformer, equipment designed to clean up harmonic noise or a UPS.  For me a UPS is the easiest solution. If your serious you can rent a power analyzer meter that will tell you what's going on with your power over a defined period of time.
 
Rocky
 
 

mike_mccue
A point to keep in mind, we tend to think about maximum capability of a circuit while the safety guidelines are more concerned with providing a trip point or circuit break at a low enough level that it actually saves a life.
 
In other words, a small appliance plugged in to a circuit that has a 50amp breaker may kill you with 15 amps because the breaker never switched to safe when a smaller breaker would have.
 
I think that when you are accustomed to stacking a bunch of gear on circuit that sometimes you can forget what the breakers are for.
 
best regards,
mike

Absolutely. Ground Fault and ARC Fault protection take it a step further. 10 milli-amps can kill a human if it's applied across the heart.
 
Rocky

Current plan is to pull control room PCs off the house circuit and onto the dedicated circuit w the racks in that room. At that point, control will be on one of the new circuits, w tracking on the other.
 
Guitar, bass, and the two sets of iso-room preamp/AD/DA gear will still be on the house circuit, however, connectionsbetween the iso-rooms, control, and tracking will be fiber optic only, ADAT via Toslink, which should avoid potential loops. There's a question whether Toslink will work reliably over the required 10 meter runs, but I am hoping that even if I have to use Toslink to Cat-5 conversion, I can avoid loops.
 
Guitar and bass are inherently noisy,  already gated, and may not need adfitional treatment, will decide that when I see how quiet the rest of the system is.
 
One interesting note, the 3 Furmann M8-Dx conditioners on the tracking room racks all report dufferent line voltages, usually a spread of 3-6 volts, unpredictable, even though all on the same, dedicated, circuit and duplex.
 
Mike, your note regarding breaker sizing and intent implies another potential issue, not as serious as personal injury but  of interest to studio operations all the same. If breakers on circuits are meant to avoid injury, not necessarily yielding advertised current supply, when they trip, computers go down with them if not on UPS, and my experience with Windows based PCs shows significant risk to file and operating systems when that happens.

I haven't used a UPS at my home since I had one burst into flames while I was sitting at my desk with Win NT3.5.
 
Luckily, I'm calm under fire, so I grabbed it, threw it outside, and got a hose pointed at it before it did too much damage.
 
I wouldn't try to talk some one else out of a UPS but I decided to pick my poison and take my chances with Windows 7 instead of the option I experienced.
 
:-)
 
 

not to be contrary, but...
 
In a properly designed studio you can have a noisy ground system and it won't make a difference, your audio will be quiet. This does NOT mean that you should ignore the technical power system, and especially the ground portion thereof, but you need to realize that you don't even need a ground - except for safety. In a properly designed studio the audio devices do not reference ground.
 
A UPS does not take the place of a series mode surge absorber. A UPS will absorb a transient, but it won't be pretty, and you will need a new UPS<G>!  The other issue is that some UPS schemes generate a great deal of electrical noise, and dump it back into the power system. In a properly designed studio that won't be a problem, but why add to your potential trouble spots?
 
You should be able to feed your studio from both legs in your main breaker panel - they both reference the same entrance ground, and therefore the same neutral.
 
Best advice thus far... if you do not feel 100% comfortable doing, or even specifying the work then get some help from a qualified electrician that understands technical power systems.

Rules for the average guy:
 
Any wiring connected to a given breaker has to be rated for the current the breaker can supply.
Use GFCI breakers for the circuit for maximum protection.
Invest in good quality power bars with AC filtering, most come with insurance on your gear.
Never run audio on circuits connected to kitchens or bathrooms.
 
If you do this, you should be safe, and noise will likely never be an issue. In music studios there's a possibility of grounded and ungrounded equipment being used. If you have the entire circuit protected with a Ground Fault Current Interrupter, it could save someones life and help you avoid serious liability. Make it safe before you make it pretty. If you follow those 4 steps, any noise is likely due to a specific fault that can be hunted down and fixed.

an excellent overview John.