House Amperage vs Stereo Amperage

Sean-

You are perfectly correct, of course, and one can draw more than 15A from a 15A line for varying periods of time. My point remains that the performance of any amp from an honest manufacturer is specified on the basis of a 15A line (whether they cut corners on the power lead or not).

The preactical limitation on performance is whether, considering everything else that may be in the system or on that power line, there are 15A available for the amplifier.

Kal

One thing to keep in mind:

A 15A branch circuit is designed to provide somewhere in the neighborhood* of 15A under steady load. Circuit breakers are thermal devices - if the load on the circuit increases above the max capability for a significant length of time the circuit will heat up and the breaker will trip.

The breaker will allow instantaneous loads of much higher than its nominal capacity to flow through. Thermal circuit breakers are relatively slow to react, so an amp can draw a large amount of current when necessary without causing a breaker trip. Only when the overload is prolonged will the breaker trip.

Therefore, most power amps made for home use will do fine on a 15A circuit. If more is required, special circuits and power cords will be mandated by the manufacturer (e.g. Levinson No. 33 monoblock).

* The actual current available is dependent on several factors, including temperature/humidity, age of the circuit breakers, condition and size of wiring, utility power output, etc.

Feedback around an audio amplifier enables it to properly follow the signal input even if the "rail" voltages fluctuate. If the rail voltage diminishes, the transistor (or tube) is just turned on more. I am sure everyone is familiar with the way that a power amp will continue to play for several seconds after it is turned off. During these several seconds the rail voltage "sag" is catistrophic, but there is little immediate audible effect.

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.