Dedicated circuits

@dhite71

Here is an article by Nelson Pass written for a layman to read on how a power supply works.  

Power Supplies: Commentary for Consumers by Nelson Pass

In an amplifier, your utility, house wiring, power cord, and transformer provide the rain. The capacitor bank is the reservoir. The capacitors receive electrical charge every 1/120th of a second, reflecting two pulses of current from the transformer for every cycle of the 60 Hz sine wave provided by the power company.

These pulses are of relatively short duration, and it is up to the power supply capacitors to store energy during the 6 millisecond or so electrical drought that occurs between charge pulses. We want a constant voltage (water level) from our power supply, and this is usually achieved by the use of large capacitors which store more charge, and large transformers which provide as much charge as is needed. You get the idea.

Since we are not designing amplifiers here, but rather trying to get a handle on what constitutes quality in a market full of hype, I want to talk about some general ideas and comment on some of the common approaches used by manufacturers. Understand that we simply want a constant, noise-free, voltage to be available from a power supply, regardless of how much demand we place on it.

Problem, for the above to happen the AC mains must be able to supply the demand of power, (volts X amperes, VA), the power transformer calls for instantly as needed. IF the power transformer is called upon to deliver more power, and the AC mains voltage drops due to a quick increase of current demanded by the primary winding of the power transformer, caused by an increase of current  demanded by the amplifier section of the amp. Then this happens:

@jea48   You are right - there will be no current thru rectifiers until capacitor voltage will drop below rectifier supplied peak voltage. 

 AC mains voltage drop, because the branch circuit wiring was not able to maintain a constant steady voltage. Reason, voltage drop was due to the branch circuit wire size. Also the length of the branch circuit wiring times two. Size of the wire and length X 2 go hand and hand.  

IF there is an AC mains voltage drop on the primary winding, of the power transformer in the amplifier, there will be a voltage drop on the output of the  High Voltage secondary winding. IF the secondary winding peak voltage is lower than power supply electrolytic caps peak voltage the AC to DC bridge rectifier will not fire. Electrolytic caps will not be replenished. Amplifier power output is lowered. If there is another high dynamic musical passage, during the event, the amplifier may clip and you may hear distortion... Depends on how hard you are pushing the amp.

If Nelson Pass over sizes his power transformers, it stands to reason the branch circuit wiring that feeds the power transformer should be over sized. 

FYI, ARC over sizes there power transformers as well as PS Audio. By bet is most High in equipment designer/manufactures do.

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Nelson’s comment on the brief intervals of power inflow from the wall with capacitors used to fill the gaps makes clear to me the reasoning behind the Multiwave feature in my PS Audio regenerator. It extends the peak of the sine wave to allow for a longer period of inflow. 

@zlone 

I doubt the PS Audio regenerator would handle the load of two Audio Research REF 160M mono block amplifiers.

PS PowerPlant 20

Maximum continuous load, 2000VA

2000VA / 120Vac = 16.67 amps max

Maximum peak load, 3600VA

Peak is fast quick draws of current. Lasting how long? Millisecond duration?

3600VA / 120Vac = 30 amps max.

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ARC TECHNICAL SPECIFICATIONS

 Power output:

 140 watts continuous from 20Hz to 20kHz. 1kHz total harmonic distortion typically 1% at 140 watts, below 0.04% at 1 watt. (Note that actual power output is dependent upon both line voltage and “condition” i.e.: if power line has high distortion, maximum power will be affected adversely, although from a listening standpoint this is not critical)

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Power Requirements per Monoblock

105-130VAC 60Hz (210-250VAC 50Hz) 400 watts at rated output, 700 watts maximum, 260 watts at “idle”, 1 watt off.

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I am pretty sure the 105-130VAC line voltage does not mean the amp will function properly if the AC line voltage is not steady. I doubt the high DC voltage section of the power supply has voltage regulators.??? 

Playing music with high dynamic passages at a moderated to high volume level could very well reach 700watts X 2, maybe more. Does the 700 watts  take into account fast, quick, short high dynamic passages of music being played?

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Voltage Drop Calculator 

enter,

Wire Size.

Material of Conduit.

Distance.

Load Current.

 

Enter distance of branch circuit wiring from electrical panel to wall outlet. (Distance is up, down, over, and back. Not a distance of strait as a Crow flies.)

Enter load current. (Continuous). Press Calculate.

Press Clear.

Enter estimated dynamic load current, ampere, peaks.

Press Enter

Write down results.

Next, for wire size, enter #10AWG. Press Enter.

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Food for thought:

kijanki

4,508 posts

06-07-2022 at 07:27pm 

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).

 

https://electronics.stackexchange.com/questions/329443/current-through-the-smoothing-capacitor-in-bridge-rectifier

@jea48 Good post. I think it is generally agreed to plug your amplifier into the wall, probably for these reasons. And probably also one reason that dedicated lines make such a difference.

Side note, up until recently I have had my amp plugged into the wall and not the P15. My amp and preamp are Audionet AMP1 and G2 respectively. And the G2 has a chassis grounding connection that is pretty much mandatory once you hear the difference. One limitation, if you want to call it that, of this gear is that the AMP1 only accepts single ended/RCA inputs. Based on experiments, it seems that there is a slight differential in the grounds of the P15 and the wall. Moving the amp to the P15 equalized this and took the noise floor of my system down a hair more. If it were balanced connections, this would not have been an issue.

 

@zlone, 

Based on experiments, it seems that there is a slight differential in the grounds of the P15 and the wall.

Difference of potential, voltage, measured in millivolts from a ground contact of an outlet on the P15 to the ground contact of the outlet the P15 is plugged into? There shouldn’t  be any difference.of potential. It should measure zero, nominal volts.

Or is the measurement to the other dedicated branch circuit EGC (Equipment Grounding Conductor) outlet ground contact? Again, in millivolts?

Or do you mean a resistance, measured in OHMS?