Importance of the power supply

In his review of a tube power amp in the November issue of Stereophile_, Herb Reicher wrote:

“…when you are listening to a power amp you are effectively listening to the sound of the power supply modulated by the audio signal.”

What does he mean? What about all the other aspects of a power amp? Why is the power supply so important?

An amp makes the signal bigger. It does this by providing power which is then modulated by the musical signal. If the power is perfect - a perfect flat line - every little bit of musical signal will be passed along and will be exactly the same as the musical signal, only bigger. But if the power has its own ripples, subtleties of the musical signal will be lost in the murk.

This is the reason PowerPlants make a system sound better.


The power supply in an amplifier should be considered as the transformer + the regulation and capacitors used to provide the DC power reserve to amplify the incoming signal.
If a design uses a suitably powerful transformer, large capacitor reserve (total capacity, not individual size) and good regulation the results can make an amplifier largely independent of incoming power supply. Power regeneration is a often debated issue, especially outside of the USA. It may help but it depends on your home power quality and the amplifier in question.
If you are considering power regeneration make sure you can listen to it in your system for a week or so and have the option to return for a full refund (incl. shipping) if it doesn’t perform to your expectations.

This link may help or it may just confuse.
Amplifier power

I should have known mentioning power treatment would send this thread off track.

What matters is realizing as perfect power as possible so that one is listening to the music, not to the weaknesses of the power supply.

Yes, the others have it right. This is exactly what I have been preaching for years. Think of an amplifier as a power supply modulated by a valve. The “valve” is the amp circuit. The better the supply, the kore effective what comes out of the valve.

Power aberrations are localized (even time dependent) based on quality coming from the utility (substation, transformer, transmission wiring); other major users served by the substation; even applicances in your home; and the wiring in your home. In my area, power aberrations aren’t much of a problem but older/overloaded distribution systems can be an issue.

Nelson Pass whimsically sums up power supplies:

“…we all like to get what seems to be good hardware value, and we want to know that the manufacturer has actually put some real money into the product which costs a small fortune. If you can read the specs or look under the hood, the power supply, being one of the most expensive parts of the amp, usually is a good indicator. It should be the biggest and heaviest part of the amplifier. … Get at least 15 pounds of amplifier for each thousand dollars spent.”

His full essay on power supplies and the importance of the components that comprise them is here:

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@paul - All of my component power cables are AC12, including the wall to PSA P20. Next year I’m having the electrician run a separate 20A line w/ 10 gauge romex from 200A panel. Yes, I know 12 gauge is for 20A circuit; 10 gauge has lower ohms/ft, cost difference is small compared to the labor of running a separate 20A circuit. I’m also going to make sure he has a great connection (dielectric grease) at the box and I’m securing the connections at the PSA 20A plug myself. The same as I did making sure the ends of the CAT7 were Talegartner CAT7 connections. The cost is in the labor so why would you not run a 10 gauge romex instead of a 12 gauge romex. It is attention to detail that makes a difference. In the end we want the cleanest, least impedance source for our amplifiers. The PSA P20 has 5 milli ohms output impedance; specified. In an amplifier we call that an amazing “Dampening Factor”… it is all about power! How clean, how stiff…

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@brett66 - as usual, great insight!

I doesn’t take much, just a finger paint swipe to coat the breaker interface with the bus bar, and on the conductor screwed into the breaker itself. Tooth pick helps get some in there.

It was like a component upgrade! (sarcasm) I am sure it conducts better than without, and will not degrade as quickly as without.

No reason to over rate the breaker, yes run 10awg or even lower if you have a short run and can manage it, but I’d stick with a 15 amp breaker for your protection. You’re not going to pull anywhere close to continuous 20 amp, let along the short peaks well beyond the breaker will easily tolerate, but an inadvertent short will pack that much more bang. The P20 only ‘senses’ the little door has been moved to the 20a position vs. the 15a position.

@brett66 - Yes, I agree, what is the point of going 20A breaker if it is a single run and the line is 10 gauge if you are not going to use near that amount of current. The only argument I could make is the breaker impedance of 20A versus 15A. I assume the 20A will have lower internal impedance; like a fuse. I’m not sure; however, is an interesting follow on investigation.

From the pole you want the least impedance to the PSA P20. So, looking at the inside of a low voltage CB (<1KV), it looks like the resistance (terminal to terminal) would change as a function of the CB current rating. Just sayin… :slight_smile:

Also, it would be pretty cool to take some PSA P20 measurements over a month, then add the circuit w/ 10 gauge romex, and 20A CB; then, take measurements (THD in/out) the next month and compare.

  1. Actuator Lever - used to manually trip and reset the circuit breaker. Also indicates the status of the circuit breaker (On or Off/tripped). Most breakers are designed so they can still trip even if the lever is held or locked in the “on” position. This is sometimes referred to as “free trip” or “positive trip” operation.
  2. Actuator mechanism - forces the contacts together or apart.
  3. Contacts - allow current when touching and break the current when moved apart.
  4. Terminals
  5. Bimetallic strip - separates contacts in response to smaller, longer-term overcurrents
  6. Calibration screw - allows the manufacturer to precisely adjust the trip current of the device after assembly.
  7. Solenoid - separates contacts rapidly in response to high overcurrents
  8. Arc divider/extinguisher


Depending on where you live, and the electrician, I believe if you are using a 20 amp outlet, I think the code requires a 20 amp breaker. If a permit is required, then an inspection might be too.
In 2013 I qualified for an energy assistance program that included a new furnace. Because the box with the power switch was about a foot lower, although I don’t think it would have mattered, they had to have a licensed electrician come in to run a piece of conduit, 2 wires, and put in a second box with the switch. They used two wire nuts and put a cover on the original box. My understanding was that an electrician was required either way. That the furnace guy was not allowed to do the wiring. I later received a letter from the inspector, giving me the option of an inspection, or I could sign off as satisfied. I choose the later, as I ran the 220v for the dryer, and as I didn’t have a conduit bender, I used a separate 90° elbow, which while being completely safe, might not have been to code. Seeing as it was a short run right of the breaker box, and obviously newer than all the other wiring, I didn’t want some over zealous inspector asking why there was no permit.

@ jeffstarr - I believe you are right. The inspector will see the 20A outlet in the music room and automatically look for the 20A breaker in the panel. That is a very good point.