confused about 20 amp power cables

@mintakax Said

I read the recent thread you participated in (AC Power in misc-audio), lots of good info in that thread. I may end up putting in a Furman P-2400 at some point.

I don’t know enough about P-2400 to recommend it one way or the other. Especially if you would be plugging the T+A PA 3100 HV integrated amp into it.

The T+A PA 3100 HV integrated amp has a very robust power supply.

"1000VA toroidal transformer with 120,000µF of filter capacitance."

Jmho the amp should be plugged directly into the 20A dedicated branch circuit wall outlet.

Available power at the wall outlet for this,

for very short time (millisecond pulse) at the peak of full wave rectified sinewave.

03-18-2025 at 01:02pm

is pretty much unrestricted. A 20A circuit will easily pass very short time (millisecond pulse) s many times the 20 amp breaker’s handle rating. (Same for the 10A slow blow fuse in the PA 3100 amp.

Limiting factor? VD, (Voltage Drop) on the AC mains caused by the load of the power supply on the branch circuit wiring. Therein the connected load of the amplifier playing high dynamic music at a high volume level. (Not a steady continuous load... This load, "very short time (millisecond pulse) at the peak of full wave rectified sinewave."

What determines VD on the branch circuit wiring? Connected load in amperes, length of the branch circuit wiring X two, and wire gauge size. (Remember the 20A breaker will pass short pules of current well over its’ handle rating, all day long.)

Question.

What AWG wire size did the electrician install for the 20A dedicated branch circuit? #12AWG? #10AWG?

Guesstimate length of the wiring from the electrical panel to the wall receptacle outlet? Try to include up, down, over and around lengths to the total length of the branch circuit wiring.

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https://www.stereophile.com/content/ta-pa3100-hv-integrated-amplifier-measurements

T+A specifies the PA 3100 HV’s maximum continuous power as 300W into 8 ohms (24.8dBW) and 500W into 4 ohms (24.0dBW). With both channels driven and using our definition of clipping, which is when the output’s percentage of THD+noise reaches 1%, fig.4 indicates that the amplifier clipped at 318Wpc into 8 ohms (25.0dBW). The T+A amplifier also exceeded its specified power into 4 ohms, clipping at 525Wpc (24.2dBW), again with both channels driven (fig.5).

(I don’t hold the AC wall voltage constant for these tests. With the amplifier idling, it was 121.6V; with the amplifier clipping into 4 ohms, the AC supply voltage had dropped to 117.9V.)

Just a guess measurement were taken with an RMS multimeter.

What was the base line for the AC VD measurements? What did the current, in amperes, measure on the branch circuit wiring?

What determines VD on the branch circuit wiring? Connected load in amperes, length of the branch circuit wiring X two, and wire gauge size.

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Thanks!  I believe the wire was 12AWG and the run is roughly 60ft.  Most of the advice I've received has been to plug the amp into the 20A wall outlet.

Edit:

It would be nice if a reviewer took the time to measure the AC line current at power output clipping.

From the owner’s manual specs:

Output Power* (Peak)
8 ohm 380 W
4 ohm700 W

Peak is not max continuous output power.

Just for a rough AC mains current draw calculation using 4 ohm 700W.

700W / 120V = 5.8A + unknown loses.

700W / 120V = 5.8A + unknown loses would be for one channel.

Both channels driven peak watts would be 1400W / 120 = 11.67A + loses.

Problem is my above calculations are flawed and do not express what is actually happening on the AC mains branch circuit wiring.

It doesn’t account for this.

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.

I’m not sure what type of current measuring test equipment would be used to measure for dynamic short spurts of current draw on the AC mains branch circuit wiring caused by high dynamic music passages for music being played. A regular Clamp Amp meter will not catch, register, the current draw event fast enough, imo. Unless several peaks were close together. ??? Not even sure then. Maybe an Oscilloscope?

@kijanki might be able to answer the question. And, more than likely, rephrase it better, what I’m trying to say.

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@mintakax said:

Thanks!  I believe the wire was 12AWG and the run is roughly 60ft.  Most of the advice I've received has been to plug the amp into the 20A wall outlet.

Hindsight is 2020. I wish I had asked you earlier in the thread about the AWG wire size of the branch circuit wiring. Especially before you had, bought, a 10ft 10AWG power cord made.

  60ft 12ga branch circuit wiring feeding the PA 3100 HV integrated amp may be sounding fine, good, to your ears. That is all that really matters.

(#12AWG is the bare minimum required for a 20A branch circuit.)

IF you ever decide to have another 120V 20A dedicated branch circuit installed for a 60ft - 70ft run, I would recommend using solid core #10AWG wire.

My first preference is 10/2 Solid core MC (Metal Clad) aluminum armored cable. Second choice is 10/2 NM sheathed Cable. (Romex, Trade Name). 

FYI, the circuit breaker will be 20A. The circuit breaker determines the size, amperage rating, of the branch circuit. Therein even if the branch circuit wiring is #10AWG the circuit breaker cannot be bigger than 20A. The connected 20A duplex wall outlet is Listed for use on a 20A circuit only. Cannot be installed on a 30A circuit.

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No worries!  Are you saying the 10AWG power cord could have been 12 AWG and would have been less expensive?