@puffbojie said:
My understanding is when connecting the amplifier to a 20-amp circuit that the amplifier will draw only the current it requires.
That is correct.
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Regarding the 20 amp circuit, vs a 15 amp circuit, would you not need a 20 amp plug on the amp’s power cord for the unit to utilize the 20 amps?
No, for the reason you stated in the above quote.
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and what if the amplifier only calls for 15?
Usually stated as minimum. Does not imply maximum of 15 amp circuit. (YMMV with your amp.) Food for thought. Why are the majority of consumer power amplifiers sold in the US designed to be plugged into a 120V 15 amp wall outlet circuit? Because the majority of wall outlets circuits found in the home are 120V 15 amp convenience outlet circuits with 15 amp duplex receptacle outlets.
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I guess the question I am getting at is: should I use a 20 amp power cord/ “plug” for the amp to match up with my 20 amp circuit?
No... When looking at aftermarket power cords for power amplifiers seldom is a 20 amp (5-20P) 20 amp plug installed on the power cord. To require a 5-20P 20 amp plug the amplifier would have to have a continuous FLA rating of over 12 amps, not more than 16 amps. In most cases a 5-15P, 15 amp plug is used. What size wire, equivalent wire size, is used for the audiophile power cord? Might be #12 rated for 20 amp. might be bigger than #12awg. 10awg is common, 30 amp rating. Equivalent, #9awg and sometimes even bigger. Well that make no sense... Especially if the in wall branch circuit is a 15 amp circuit.
My guess the electrician that told you a 15 amp circuit is all you need is going to use 14 gauge wire. 14awg is rated for 15 amps. (How long will the branch circuit wiring be? Distance from electrical panel to wall outlet?) Now nothing prohibits the electrician from installing #12awg or even #10awg branch circuit wiring and connecting it to a 15 amp circuit breaker in the panel. The circuit is still a 15 amp circuit. The breaker handle rating determines the size of the circuit. Not the size of the branch circuit wiring.
Why bigger conductors, awg wire? AC mains Line VD, (Voltage Drop) under load conditions. Not just continuous load but for audio amplifiers high dynamic quick peak draws of current caused by the musical source material being played.
Example:
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2x200W amp might take from mains close to 1kW during peaks. The problem is that peak supply current won’t be expected 8A, but rather close to 40A. It is because current is drawn only for very short time (millisecond pulse) at the peak of full wave rectified sinewave. It applies to most of LPS. Power delivered with such short pulses not only creates larger voltage drops in house wiring, but also heat-up amp’s power transformer, that has to be oversized (higher copper losses and higher core losses for eddy currents and hysteresis).
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@kijanki
+1
Please explain what happens if the power transformer’s secondary winding voltage is lower feeding the rectifier, due to a quick AC mains VD event, and the electrolytic capacitors voltage is higher. Just going from memory the rectifier will not conduct and the caps do not get recharged for that "(millisecond pulse)" in time.
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@jea48 You are right - there will be no current thru rectifiers until capacitor voltage will drop below rectifier supplied peak voltage. Theoretically it is possible to build LPS where capacitors keep average instead of peak voltage, but it requires huge inductor in series (in order of Henries) made with thick wire and AFAIK nobody is doing it. One problem is lower rail voltage (average instead of peak) while the other is dependency on the load current.
http://www.r-type.org/articles/art-144.htm
Does AC mains VD impact the sound of a power amplifier? From my listening experience it does. YMMV.
FYI, a 15 amp circuit breaker will pass quick short draws of current well above its’ 15 amp handle rating all day long without tripping open. The breaker doesn’t see or care about VD on the wiring.
FYI if you have a 15 amp branch circuit installed, per NEC code you cannot install a 5-20R 20 amp duplex outlet on the 15 amp circuit. I believe that most of the audiophile outlets sold today are 5-20R 20 amp outlets. NEC code does allow 2 or more 5-15R 15 amp outlets on a 20 amp branch circuit. A duplex receptacle is two.
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