AC Mains Past 20 Amps

rumleymusic
Most studios will use power conditioners just in case.  Though usually any properly wired building will not have ground loop problems.  20 amps will get you well over 2000 watts of power, plenty for everything in most modest studios.  Though there shouldn't be a problem adding a second circuit either from the main box or splitting a 30-40 amp circuit breaker into two sub panels for separate rooms. Usually the ground point will be shared by everything.  

Thanks, Daniel.
 
I have 3 circuits in play presently.
 
One, 20 amp, original house wiring for the west end of the house, three bedrooms, a bath, and the west walls of the living and dining rooms.
 
Two, a 20 amp home run installed recently solely for audio use, one two duplex receptacle, feeding a chain of fair to middlin 6 ways, tiered for easy on/off in banks.
 
Three, a 20 amp home run installed recently with a single duplex in the tracking room, and another in the control room adjacent.
 
I need to get meters inline to see what I'm drawing now, and also get a few pieces of audio gear off circuits 1 and 3.
 
I have a  Chauvet light board, several LED parcans, and a DMX transceiver pair on circuit 3, along with a drum machine, bass processors and a wireless receiver (for bass) on circuit 1, but so far, the only noise problems I have are in a pair of Lexi MX200s (which are fed by a send from main interface, with guitar amp signals present) which are analog but headed for fully SPDIF implementation soon....
 
...some noise issues between tracking and the remote laptop dock, which turn out to be unbalanced 25' runs, coulda swore I laid balanced TRS cables in there, gremlins done it.
 
...and some 60 cycle hum in the new control room, which has the PCs on house wiring circuit one, and audio racks on studio circuit two.
 
Think I can resolve most or all the issues easily, but before I do, I need to know how much is already on circuits two and three, and what my options are if I bump my head on either, with ideal configs from a noise POV.
 
You've given me options there, and I appreciate it, thanks!

:-)
 
There's an irony for me. I did some remodeling a year and a half ago. I pestered my electricians to give me a three outlet box with a dedicated 30 amp circuit for my rack and CPU then a small change in room layout, after all the paint and trim was finished, caused me to disregard that specific circuit and plug the whole shebangs into a general purpose 20 amp circuit serving the other wall outlets.
 
Best laid plans...
 
:-)
 
My home setup only has a 200 amp max house panel capability and it gets spread thin between the house, the studio, and the work shop stuff. I don't know much about power wiring in commercial facilities, other than it can be dedicated and doesn't have to be constrained to a 200 amp max mains connection. 
 
best regards,
mike
 
 
 

boy...I'd put #10 wire on that 20a outlet, especially if it's on the other side of things.  But I want to say, here in the US, you can only put one 20a outlet per circuit... but I'm a non-licensed electrician, that sees a lot of generator "backfeeding" into their house system, thru such type outlets, here in Kentucky.  (remember to shut off your mains...right!)  That typically also give you some "hot prongs" on that generator cable as well.  Great for young kids.
 
I've got a question though... what are the thoughts of using a UPS power supply as a "voltage regulator" and minimal surge arrestor, as compared to these glorified Furman "power strips"?

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.

an excellent overview John.

so this may be going a bit far afield for a forum post, apologies if that's the case!

There are two ways to address electrical noise problems in a studio setting - you can deal with it at the source, or at the destination<G>. Noise is a given, and it is only going to get worse!

Noise is not, however, the problem... noise entering audio circuits is the problem!

I would never EVER suggest that you should not start with the quietest possible power system... that's just plain common sense. Less noise means it is easier to suppress it!

BUT, not everyone can start with a clean power and grounding system, so it is important to understand how noise gets in. And how you can mitigate it.

The first problem is single-ended interfaces. I don't want to sound like a snob, but single-ended inputs are a huge problem waiting to happen. Single-ended outputs pose less of a problem, but ANY TIME you share one conductor for signal return and shield you are starting out at a disadvantage.

Sadly, many manufacturers have forgotten the lessons of the past, and connect the shield in a balanced input to the circuit board. This is referred to as the "Pin-1 Problem", and it has been covered in great detail since 1995. If you search for "Pin-1 Problem", and Bill Whitlock or Neil Muncy or Jim Brown you'll find lots of material. The short version is that the shield should always be connected to the enclosure, and never to the circuit board.

Back in the 1990s I rebuilt an old analog console. One of the things I did was install a large copper buss bar, and I connected ALL the shields to that buss bar. At the time I assumed that the buss bar was responsible for the remarkable improvement in S/N ratio. Now I'm not so sure, I think it probably had more to do with removing the shields from the motherboard. One of these days I will test this hypothesis and report back.

What all of this points out is that a balanced interface is ideal, and that proper interconnection between a balanced source and a balanced input, including keeping the shield outside of the enclosures, and using cable with a braided or  Reussen shield instead of a foil shield, and no drain wire, and a tight, uniform twist. All of these things matter.

If you don't have balanced outputs then you can get the same noise suppression by wiring the connection as it it were balanced. There are lots of how-to documents, I recommend Rane App Note #110. Bill Whitlock has also written about how a single-ended source need not degrade performance of a differential input.

If you are dealing with single-ended inputs there is little you can do, other than balancing them. You can use transformers (use an input transformer, there is a difference) or you can build a transformerles input, the easiest way is to use the THAT InGenius(tm) chips. It isn't as expensive as it sounds if you only have a couple of inputs.

And putting to rest a myth that just won't go away... cable shields do next to nothing for typical noise problems. Twisted pairs and differential inputs do most of the heavy lifting. Shielding is only effective at radio frequencies, at power line frequencies the twist is the magic.

Speaking of which, if you are installing new power circuits consider using twisted wire from panel to outlet. It is available, it isn't horribly expensive, and it meets code. There is even a version that is shielded, and if you do have a lot of RF hash on your power lines it is quite effective.

That's probably enough general stuff for now... feel free to ask questions!

In the meantime for Jay Tee - for your equipment that is on the old power circuits...

Can you confirm that this gear is the only gear that is acting up, and if so does it act up when connected to gear on the new power, or stand-alone, or both? There are a number of potentially (pun unavoidable) inexpensive solutions that might help.
 

Good stuff wst3. 
What popped into my head while you were explaining the pin 1 issue , is how many folks have issues with usb buss powered audio interfaces. Personally I don't recommend using buss power for audio interfaces. 
I owned a buss powered Fast Track pro that I gave up on because of a hi pitched noise. Later reading many posts by others with this issue I realized that this was a common issue with all buss powered interfaces. A special USB cable will solve the problem,, but to me that's not acceptable. 
 
My studio was wired by a guy who wires hospitals and even though we opted out on the orange outlets ( $$$) he used  isolated grounding. 
 
The main reason my friend advised keeping motor loads off your studio circuits was more for load draws that happen when they kick in. I have a friend who's lights go dim for a second every time his pump cuts in. Of course this all goes back to how a home was wired. People tend to go with the minimum. My gang likes to overbuild. Where the code allows for the 12 outlets, we use 8 to 10. My friend with the pump issue used #12 wire and the run is 200'. He will be replacing his burned out pump as a result. My pump has #10 wire @ 150' My lights don't go dim. 
 
Which brings us back to wire size/ breaker size. This is for Canada /USA. 
I'm just quoting from what I understand and not from a professional view so bash me if wrong. 
In a workshop we need heavy duty outlets for power tools and motor loads. 
In a house, all appliances will never exceed the need for a standard 15 amp breaker. 
Therefore household circuits are standardized to handle the potential requirements of each room. It is also standard practice to balance the rooms with the circuit sharing lighting and outlets. Last time I looked this was 12 per circuit. It seems to change. 
#14 wire is also standard as that matches the current requirements of 110v/ 15 Amps. 
If you were to use #12 wire this would absorb more heat from an overload and the breaker might not trip as expected. 
So as far as I understand you match the wire to the breaker. 
#14 = 15 amp 110V
#12=  20 Amp 110V 
Sizes beyond that are then usually 220V . Reason being of course is as the voltage this doubles the available watts without requiring larger wire or breakers. 
Example, most electric baseboard circuits are#12 wire and 20Amp breakers. 
 
Anyhow ,around here nobody will have 20 Amp Household circuits in living rooms and bedrooms. They would be considered dangerous. 
 

Cactus Music
 #12 wire and the run is 200'. He will be replacing his burned out pump as a result. My pump has #10 wire @ 150' My lights don't go dim. 
 
Which brings us back to wire size/ breaker size. This is for Canada /USA. 
 Last time I looked this was 12 per circuit. It seems to change. 
#14 wire is also standard as that matches the current requirements of 110v/ 15 Amps. 
If you were to use #12 wire this would absorb more heat from an overload and the breaker might not trip as expected. 
 
Anyhow ,around here nobody will have 20 Amp Household circuits in living rooms and bedrooms. They would be considered dangerous. 
 

 
Wire length with a fixed resistance per foot, times the current of the load, equals a voltage drop across the wire distance. If the voltage at the load is too low, the device will not function, and may burn up due to overheating as it tries to run on a lower voltage. This will burn up a pump. A larger wire will display a lower resistance per foot, allowing the voltage to be higher at the load. I deal with this all the time when installing fire alarm signaling circuits and the horn strobes we place on those circuits.  the larger the gauge of wire, the less voltage drop across the wire. Bigger is better, but bigger costs more, so many folks will use the smaller size wire on circuits when cost is a factor, like in house living room and bedroom circuits. Loads tend to be smaller so it's often not a big problem.
 
Using ohms law E over IR  and power ohms law P over IE, you can calculate the voltage drop and the power dissipated as heat in the wire. Resistance per foot is obtained from the NEC tables and appendix or google it.
 
I believe it is a common calculation to use 180va for an outlet in factoring the maximum number permitted on a circuit based on CB size. So 12 on a 20a CB would seem about right as the max number. Less is OK too. I try to limit them to 7 or 8 depending on the circumstances when I am wiring something new.
 
#14 ga cu wire is correct for a 15a CB.  Using a #12 cu wire would be OK too. The larger wire does not "absorb" more heat. The CB will still trip at the correct level of overcurrent. The CB's trip based on 2 things.... one is heat build up over time in the circuit breaker (not the wire) .... this is the reason a circuit for continuous duty (3 hrs or more non-stop) is derated to 80% or 16 amps on a 20amp CB. The other reason it trips is due to the magnetic field created by the current. Some CB's are designed to be used in motor applications and will hold 2 to 3 times their rated current for a very limited time. These breakers have a special marking to indicate this. Usually about one and a half seconds is all they will hold depending too on the level of the current. This is to allow a motor or a compressor to start properly. I have metered 50+amps on a 20a CB on motor start and the CB holds..... but not for long. In a locked rotor condition....click after 2 seconds or less.
 
A 20 amp circuit is no more dangerous than a 15 amp circuit. Size the wire and breakers correctly and they are both just as safe. I would prefer to have 20a circuits over 15a circuits because they can hold a larger load.
 
In my old house, some of the wiring is certainly not up to today's code requirements. It's not dangerous, just that the bathroom circuit also feeds other rooms. So a few times, my wife would be using the blow dryer and the hot curlers and the TV was going and a few other things like some lights, when suddenly, the 15a circuit breaker tripped.

"Using ohms law E over IR  and power ohms law P over IE, you can calculate the voltage drop and the power dissipated as heat in the wire. Resistance per foot is obtained from the NEC tables and appendix or google it."
 
2KIL/CMA is the voltage drop formula. K= constant which is 12.9 for copper, I = amps of the required load, L= distance to the load in feet. Circular Mill Area ( CMA ) can be found in the chapter 9 of the NEC.
 

"A 20 amp circuit is no more dangerous than a 15 amp circuit. Size the wire and breakers correctly and they are both just as safe. I would prefer to have 20a circuits over 15a circuits because they can hold a larger load"
 
Absolutely... You won't find 15 amp branch circuits in commercial buildings. You would be pretty hard pressed to get a breaker to trip using your body as the load. GFI and ARC fault protection are much better at this.
 
It seems this thread has split into two separate topics: power quality and electrical safety.
 
Rocky

Bill, I can't confirm specifics right now, but I will when I can. What I know at this point is three areas of noise, spread over four rooms of equipment. Guitar and bass I'm not worrying about at this point, if ever, leaving twoIissues.
 
In the control room, interfaces, pres and processers are on the new circuit, while both PCs are on house wiring. I get hum when both interface outputs are into the small mixer. Either by itself, no prob. First move there is to get the PCs onto the new circuit and see whats what. Theres a nest of surge protectors involved, which allow the WAN demarc, firewall, and switch to remain up fulltime, ISP requirement, and another switch that goes up and down w the PCs, pkus a third layer to allow me to power off the  video monitors while the PCs stay up. Ima have to move that carefully to preserve that functionality, hence the delay.
 
The other issue is in the listening room, where feeds from a laptop DAW for remote recording, come together w feeds from the tracking room, thru a mixer into flown stage monitors above a large LCD. TR is on a new circuit, laptop and monitors are on house wiring. 
 
Tougher to get them off the house circuit but may not have to. Part of the current upgrade is to connect tracking, control, listening/laptop, and an iso room together. Backbone is ADAT via lightpipe thru an Optiplex +. There's an excellent chance the noise issue will disappear when the balanced audio runs are replaced w fiber, since selective unplugging negates it now.
 
More as I have it, and thanks! Much help!