Dealing with a power amp that need 20A connection

I purchased an ARC 150M two channel.
The amp has 10A fuse, so I guess it is fine with 15A receptacle.
I bought an adapter, not a cable, and use the adapter with my 12 AWG power cable. I ordered 10 AWG power cable with 15A male and 20A female, and I will get it in two weeks.
I also changed the receptacle with a PS audio power port classic receptacle.
I am listening at a low ~ medium volume level, fearing trip the circuit breaker. I feel it sounds at least as good as my Plinius 102A. Maybe a little bit more clear and bright sound.
Thanks for all the comments and help.
I just feel so dumb to purchase this amp without even knowing the different type of power connector for 20A. ;-)

I am listening at a low ~ medium volume level, fearing trip the circuit breaker.

You can crank the volume up as much as want. The 10 amp Line fuse is a lesser value than the 15 amp breaker. The actual FLA on the amp is more than likely 8 amps or less. (8 x 125% = 10). Keep in mind that is continuous amps. Pushing the amp full bore. The 15 amp breaker will handle a continuous load of 15 amps all day long. It will pass short spurts of current well above 15 amps all day long. (Of course you have to take into account any other loads that are connected to the same branch circuit).

Your problem with the 15 amp convenience outlet branch circuit could be/will be VD (Voltage Drop) if you push the amp to hard. Basically starving the power supply of the amp. The caps in the power supply will have problems recharging.

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Subject line is in regards to a power cord but the same would hold true (probably more so) for a 15 amp convenience outlet branch circuit for the amp you have.


Ralph - Manufacturer, Atma-Sphere Music Systems

There are two aspects, AC voltage drop and high frequency current limiting.

AC voltage drop is the voltage dropped from the wall to the input of the equipment in use. I’ve measured a loss of 40 watts on an amp that makes 140 watts, so no-one should be surprised that that might be audible as well. I used a 3 1/2 digit DVM to measure the voltage drop and it showed around 3 volts. This was a pretty standard but inexpensive Belden cord. A more expensive Belden cord with heavier gauge showed a lessor drop and more power out of the amp. So no mystery here.

The second issue is the high frequency current limiting. This is a bit trickier to understand, but its not quite rocket science. Almost any power supply consists of a power transformer, rectifiers and filter capacitors. When the the transformer voltage is higher than the capacitor voltage, the rectifier commutates (a fancy word for turns on and conducts). At that point the filter capacitors can charge up and will do so until the power transformer voltage falls low enough that the rectifiers cut off.

At that point the circuit using the power supply drains the filter caps. Since this happens 60 times a second, the drain is usually not very much at all, so its only at the very peaks of the AC waveform that the caps are be replenished. There might be only a few microseconds or milliseconds that this can happen, and quite a bit of current might have to flow during that time, essentially a high frequency event.

If the power cord limits current during this period, the performance of the circuit using the power supply might suffer, possibly due to increased IMD since the DC might have a bit more of a sawtooth on it than if the current was not limited.

https://www.audioasylum.com/audio/cables/messages/17/174988.html


Nelson Pass
https://www.passlabs.com/press/power-supplies-commentary-consumers.



ARC recommends a 20 amp dedicated branch circuit. See page 2.
http://www.audioresearch.com/ContentsFiles/150M%20Manual.pdf

Why not contact ARC for guidance instead of asking others who clearly have no idea of the actual requirements?

I contacted ARC service and asked a question about this amp over two weeks ago, but no response yet.
Most of time, it is more responsive and sometimes more detailed response I get from online forum than the manufacture's customer service. 
So far so good at moderate volume (9 o'clock position).

@ ihcho

Did you read page 2 of the 150M owner manual?

Either ARC had a lawyer write it, or ARC just stopped some guy off the street to write it.

Quote from page 2.

The AC power source for the amplifier should be capable of supplying 15 ampere for 100 or 120 volt units,

Yeah, really? 15 amperes..... I wonder how many layman read that as a 15 convenience outlet circuit meets that statement?
I can tell you how the majority of electricians would read it. The equipment manufacturer says his piece of equipment needs a 120Vac 20 amp circuit.

Here’s the thing though. Technically ARC meets UL, and NEMA safety standards. It is also in compliance with NEC electrical code. The continuous (repeat continuous) FLA of the amplifier is not greater than 12 amperes. That complies with NEC, UL, and NEMA, electrical safety standards for a 15 circuit.

And then in the next paragraph it says;

For the very best performance on domestic 100 or 120 volt circuits the 150M should be connected to its own AC power circuit branch protected by a 20 amp breaker.

its own AC power circuit branch protected by a 20 amp breaker.

Normally it would be worded, 20 amp branch circuit. Per NEC the overcurrent protection device, breaker in this case, determines the size of the branch circuit.
For a 20 amp branch circuit the bare minimum branch circuit conductor, wire, size is number 12awg. You can go with a bigger size, but not smaller than #12awg.

So why all the dancing around the branch circuit size ARC recommends for the amplifier? The vast majority of homes in the US convenience outlet circuits are 15 amp. (15 amp breaker, #14awg wiring). Living rooms, bed rooms, dens.
Jim