# Blow a fuse?

Discussion in 'Recording' started by corl45, Jul 25, 2010.

1. ### corl45Active Member

Alright, so soon my and my buddies will be jamming out, and recording a little bit of it (more jamming than recording) and I'm bringing over my audio equipment, plus all of our amps. We will be in a rather small room (size of a bedroom roughly, maybe smaller. As the room is at my buddies house so I do not have dimentions) and have a bit of equipment:

2 30w bass amps
1 15w guitar amp
1 65w guitar amp.
another guitar amp prob around 30w
A computer with a 300w power supply.
and a 8 input mixer.
a medium sized stero for listening

sorry, most of the equipment isn't with me at this point in time so I can't check how many amps each pull.

I don't know what his fuses are rated at but I'm assuming somehwere around 20-30 amps? The room being so small in probably on one circuit too. So i guess my question is, should I bring some extention cables and pull from other parts of the house with surge protectors? and how many amplifiers can I put per circuit?

2. ### SpeedskaterActive Member

I don't know where you live, but if it's in the US then the fuse/breaker is 15 or 20 Amps. That's not a lot of equipment, if you turn your setup on, one unit at a time you should be OK.

3. ### dvdhawkWell-Known Member

+1 to Speedskater - good advice as always.

And if you don't know how to figure it, the maximum power consumption ratings should be clearly marked on each device and may be to expressed as amps (amperes), milliamps, or watts.

To convert wattage into amps the equation is easy division: watts/volts=amperes (amps)

If you live in the US where standard voltage is 120V the math is simply as follows: Total# of watts / 120 volts = amps

For example: 120 watts = 1 amp, 180 watts = 1.5 amps, 240 watts = 2 amps [to use round numbers] 470 watts = 3.92 amps (using your values)

and obviously 1000 milliamps = 1 amp. So you multiply the milliamps by .001 to express it in amps. (basic math)

For example: 1250 milliamps = 1.25 amps, 650 milliamps = .65 amps

If you can throw together a spreadsheet, just make sure keep a separate column for each label type. Add up all of the devices expressed in amps. Add the devices expressed in watts and convert the total to amps, add the milliamps and convert them to amps. Then you're adding amps to amps to amps.

Also, judging power consumption by the power output of an amp is ok for an estimate, but to get the real maximum consumption you need to check the labels that should be on each of the electrical devices you're using.

Your devices will be rated (and fused) for absolute maximum safe working limits. So unless you're blowing fuses on your amps regularly (which you should take as a warning sign) your gear is working well below those max. ratings.

I hope that makes sense. Good luck!

One device at a time of course. But those don't seem all that needy IMO. Assuming fairly recent construction of said dwelling. I run into trouble on this 1970's-ish trailer when I run 2x 225W monitors, 450W HDTV, 450W Desktop from the same plug. Minor tinge of something burning in house (like someone smoked a cigarette down to the filter part), but the fuse on the pole outside blew before anything in the house popped. An extension cord for the computer might be a safe bet. Keep it on a different circuit. That way if something does blow, the computer is kept on the better odds of the equation.

120W = 1A or at least that's what I've heard for rating battery life relative to inverters and the likes. My laptop is rated at 1.7A, so a 200W inverter minimum to run it on batteries + inverter via AC plug. Another option if you're that concerned. Yamaha makes a reasonably quiet generator if you want to play it super safe. Assuming facilities to accommodate. And run the generator outside of course.

Generally, I would say that if you would put all your amps on the circuits in the same room, assuming that we're talking something like a basement or other standard residential room (living room-ish) you should be ok... WITH the caveat, that NONE of the amps is going to be driven very hard... e.g. less than 1/4 of the way up. (which would be intolerably loud to even think about recording)***

Since you are talking about a "bedroom" sized room, I will venture that you should only put one of the larger amps on that circuit, and the two smallest amps. Do the same with the remaining amps, by getting power from another room, and run them with at least 14 gauge extension cords into the room.

I would run a fairly good sized extension cord (12 gauge) from another part of the house, for your computer, mixer, and other recording gear.

To be honest with you though, that many amps in one tiny bedroom is going to be incredibly loud, unless you barely crack those amps open... much less getting anything tracked that's not going to wind up seriously distorted, or bass heavy to the point that it's all you hear.

*** Most modern residential wiring in larger rooms have greater odds of having two or more electrical circuits... but this is no guarantee.

7. ### dvdhawkWell-Known Member

I wouldn't assume 30 amps. Of course it's possible, but I think in residential wiring 15A & 20A are by far the two most commonly used breakers. And if they cut corners, or the wiring was done a long time ago, there's no guaranty that each room is even on its own fuse/breaker.

Do your arithmetic, I'll be shocked if you're drawing more than 15-amps (1800 watts) with the equipment you've listed running full-bore.
You just won't be able to use your blow dryer and toaster oven on the same circuit while you're jamming.

[Even the heating element in the toaster oven will shut off and coast for a while once it hits the temperature established by the thermostat.]

8. ### corl45Active Member

Alright, thanks guys. I only ask because I'm pretty big into computers and I know usually 3-4 computer per circuit is the limit, or recommendation. But thanks all makes sense and good advice. I'm running all the amps inside the room, and the mixer and computer outside the room with an extension cable (didn't get the gauge on it, but it's pretty thick).

I power up my entire Remote Truck with central HVAC and a power gobbling electrical isolation transformer from 2 standard 20 amp Edison House power outlets. Of course, I don't have the guitar amplifiers nor a PA system in use. But hey, at that's like running an entire home on two outlets. And while I also have my share of computer-based stuff onboard, I make sure I have the UPS on that stuff. Nobody should be doing this stuff today anymore without using UPS's's's..'s.

I think the biggest problem you are going to experience is ground loops. And while everybody would like you to practice safe grounding techniques, you are quickly going to discover the need for some electrical ground lifting. But remember, lifting any electrical ground to prevent audio electrical buzzing from ground loop can be potentially deadly. This is of a particular concern especially with guitar amplifiers and PA systems. But unless you're going to build all of your own audio cables this will be an unavoidable issue. Especially when you have your recording equipment on one circuit and the band equipment on the other circuit. This is where the danger lies. That's why it's so important for folks in the audio business to know and understand how to use a simple AC/DC voltmeter. 120 V from the strings on your guitar to your lips touching the grill of the microphone has zapped many a rocker. Do you suppose that's where the expression death metal came from? Have you ever seen the metal grill of an SM58 get welded to a stainless steel beer cooler at a local bar? I sure have. We all had a good laugh since no one was killed except for all of the equipment. It's okay, it wasn't my equipment. Not my gig. It sure was cool prying that SM58 off of the stainless steel cooler. I never knew that SM58's liked Budweiser?

Boom! Zap! Sparks a flying.
Mx. Remy Ann David

Of course take precautions. Don't be zapping hot pockets or popcorn in the microwave during the jam. Or running a load of laundry. Dishwasher, and even that pesky A/C unit can alter the demand significantly. All of my mics / preamps and recorders run on batteries. Or at least have the option to. And my laptop has a battery too. No loops or other changes in performance under a load since nothing else is on the same circuit that way. But that doesn't mean that if the A/C, refrigerator, freezer, water heater, and whatever all turn on at roughly the same time that there wont be problems. Or if your power company just sucks. Throw in a good storm or a bad driver down the block. Recalling my days in army barracks when they were being remodeled WHILE we were living in them. Burning up a tape backup drive in the process with the power flicking on and off every five minutes. Keeping a battery powered radio for entertainment handy for the 2+ hours every sunday that there wasn't any power. Plus a plethora of flashlights to shower in the dark and otherwise get ready for work.