House Amperage vs Stereo Amperage

Sean has a point, but... If an load device has the ability to draw more than 15 amps (steady state) it will not be certified by UL to be furnished with a standard Nema 5-15 (straight two prong one ground)power plug. If your product is designed to draws more than 15 amps on anything more than a transient basis and you equip the product with a 5-15 plug you are violating UL and NEC rules and leave yourself open to both civil and criminal liability if injury or property damage results.

There is no doubt that a load higher than 15 amps may be drawn for very brief periods(such as motor start or musical peaks)but, as noted earlier, these loads are transient. HD motors and audio-amplifiers usually have capacitors specifically to cover this temporary situation.

If you think your Sunfire can draw more than 15 amps steady state (no matter how inefficient the load) just hook it up to a Kill a Watt and use a test record for whatever frequency you want for as long as you want. I would be amazed if you show a 15 amp + draw and/or you pop a 15 amp breaker.

The point is this is why G-d and/or the EE wizards have created power inlet/output plugs rated for more than 15 amps. My air compressor and air conditioner have a NEMA 5-20 plug and require a twenty amp 5-20 outlet and circuit breaker.

This question sometimes goes into la-la land where there is a "mine (dedicated circuit) if bigger than yours". So, put in a 100 amp 4ga circuit if you must for your 100/100 watt amp. It might make you feel good but the electrons won't care.

Whilst the above discussions are all technically correct concerning wall plugs, UL, current draw by the amp, etc., has it occurred to anyone that Doc777 maybe confusing the current capability often quoted by big muscular power amps ?
This includes Sunfire, Musical Fidelity, Harman Kardon etc who frequently quote high current capability to drive difficult loudspeaker loads.
Currents way in excess of 30A are often quoted which is not so difficult to achieve with the higher power solid state amps.
With a typical 50Vdc rail voltage, and an extreme steady state case, this 50Vx30A=1500Watts and still within the 1725Watts of your typical wall plug.

Chipman...A good observation. I suppose one could have an amp with ten volt rail voltages that could put out 150 amps, which would be 1500 watts. It would probably work better as a welding machine than an audio amp.

Many thanks for all the help. Initially I felt my question might have been too "newbie" but I find my others concerns were answered too, like a dedicated 20 amp line etc. I love this room!

Kal: If what you say is true i.e. that all "legit" manufacturers power ratings are based on a 15 amp AC line feeding them, there are quite a few products and manufacturers that are either lying or lack ethics.

Rex: Your response about products and manufacturers providing what is needed to operate them is all well and good. One question though. Do you think that all manufacturers provide what they should when one is operating a product at capacity under the worst conditions? On top of that, do you think that the bean counters at these companies think about this when they are trying to cut production costs to the bone and increase profit?

As far as breakers go, breakers tend to deteriorate with age. As such, a 15 amp breaker can become "soft" with age and become marginal in terms of performance with as little as 10-12 amps of current drawn through it. This is not to mention that connections develop corrosion with age, reducing current potential. Rex did correctly point this out in his post above.

El: I don't know what you are thinking here, but it surely doesn't have anything to do with audio. If voltage sags during a high duress peak, leaving the transistors on for a longer duration will not correct for the lack of dynamic impact that was lost. If the power is not there when it is needed, you can't correct for that later. Loss of amplitude is a distortion of the original signal.

As far as your example about an amp "playing on" without an AC feed present, how long and how well an amp will do this is directly related to the power supply reserve ( capacitor bank ) and how efficient the amp is.

To shoot a whole in that theory as far as audibility of distortion goes, if one has the system cranked and AC sags drastically, the available power falls drastically as the distortion increases. The sound will only remain satisfactory so long as the peaks are reproduced at full amplitude. Once peaks of sufficient amplitude are encountered that tax the power supply reserves, clipping and the associated distortion and power drain set in rapidly.

One has to remember that most amplifier designs are NOT regulated and that many of the newer designs use "power tracking" circuitry that directly follow the rails of the amp. Sagging of the rails will basically cripple this type of amp. The earlier Carver Pro amps ( which aren't actually Carver designs ) are of this variety. They become useless when AC starts dropping rapidly. I know this as i've worked with them in small clubs and had them "browning out" on me due to limited AC supplies.

Zorpman: As i mentioned above in response to Kal, either a lot of manufacturers of BIG amps are lying about their low impedance power potential or the UL is slacking to a very great extent by allowing a lot of "unsafe" products to be marketed wearing their badge of acceptance.

As i mentioned above, the Kill A Watt is NOT accurate under dynamic conditions. I've called the company and discussed this with their "technical department" ( ha ha ha ). Their response was that if you measure a light bulb, it will give a reasonably accurate reading. If you pulse power on a dynamic basis, the circuitry may not have the required transient response to follow the actual electrical demands of the DUT ( Device Under Test ). As such, the Kill A Watt should be used for power averaging and may not even be accurate for that. Having said that, it is a handly little device when properly used and i've done so many times. Sean
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PS... Many of my examples in this thread take things to the extreme. Under most cases with most amplifiers operating under what most would call "normal use", a solid 15 amp line will be more than enough power to feed a two channel amp. Then again, the amp is going to pull what it needs, so if there are other components on the line, the amp may end up "robbing Peter to pay Paul" in terms of starving those components. This is why many folks run dedicated lines for the amps with separate AC feeds for the line level gear. This equates to reduced voltage sag for the entire system.

If you've got a big high bias amp, like to listen loud in a big room with low impedance low efficiency speakers, you might want to think about running a heavier line. I have six amps running in my main system and they are all "high bias power suckers". My HT system is rated at 6400 watts RMS. My office system uses 800 wpc monoblocks. My bedroom system is bi-amped. Now you know why i consider "weak AC" a REALLY bad thing.