Analyzing the power from the outlet

The previous discussion to which Lak refers, of essentially the same question, was in this thread, beginning with the post the link opens at.

As you'll see, IMO measurements of AC noise, even with sophisticated instrumentation, are unlikely to be helpful.

I've seen suggestions to validate the outlet voltage is consistently 120 V with a tolerance of +/- 3 V. Assuming the outlet meets that benchmark, that would, I think, obviate the need for a power regenerator. (At least I think that is the function of a regenerator.)

Besides providing a stable voltage, a regenerator will also reduce or eliminate noise and distortion that is present on the incoming AC, since it is what generates the AC that is provided to the components it is powering. Essentially it consists of an oscillator generating a 60 Hz signal (or 50 Hz in some countries) driving a high powered amplifier which in turn supplies that amplified 60 or 50 Hz signal to the connected components, and a power supply which converts the AC from the wall outlet to the DC which powers its own oscillator and amplifier.

Although as you may have seen in past threads some people report that the regenerators they've tried seem to cause compromised dynamics or other issues.

It's my (limited) understanding that most audio components have a transformer as the first stage from the power input. Doesn't that automatically decouple most of the noise from the power?

The bandwidth limitations of the power transformer will significantly reduce the frequency components of the noise that are above a certain frequency. Noise on the incoming AC will also be reduced by filter capacitors and decoupling capacitors that will be present at various circuit locations in the design. It will also be reduced by voltage regulator circuits that are generally used in audio components, other than in the high power stages of most power amplifiers and integrated amplifiers. Finally, it will be reduced by what is known as the power supply rejection ratio of the amplification and other circuit stages which process the audio signal.

All of which is not to say, however, that cleaning up the AC power in some manner won't make a difference, to a greater or lesser degree depending on the specific components that are involved.

Regards,
-- Al

But I understood the amplifiers require internal oscillators to operate? Why do you need to add an external oscillator?

An oscillator is something that generates a signal. An amplifier is something which boosts some combination of the voltage, current, and power of a signal. What I was describing was a power regenerator, which takes in AC power from the wall outlet, and sends out "regenerated" AC to the components that are plugged into it. Power is regenerated in the regenerator by amplifying a signal generated by a 60 Hz oscillator which it contains. As I indicated, the regenerator's amplifier and oscillator are powered by DC which its own power supply creates from the AC it receives from the wall outlet.

If all this processing is in the amplifier, why would it matter what you do to the power before it arrives at the amplifier?

No design can reject noise and distortion on the AC it receives to an infinite degree. A substantial body of empirical and anecdotal evidence exists suggesting that designs at pretty much all price points can benefit sonically if the AC they receive is relatively clean.

Regards,
-- Al

CJK, a power filter/conditioner puts the incoming AC through a relatively simple circuit which provides some degree of noise reduction. It may also include a provision for surge protection. It does not “regenerate” power.

As can be surmised from the description I provided earlier, a power regenerator capable of supplying sufficient power for a typical audio system will cost a substantial amount of money. Many (although certainly not all) conditioners are available for much lower prices than most regenerators, or at least regenerators that are well designed and have substantial power capability.

Your question about balanced power is a good one. Yes, the outputs of the power transformer in an audio component will often be balanced relative to ground. (Although keep in mind that the power transformer will often provide multiple outputs, at various voltages, some of which may be balanced and some not, for various reasons). However a main goal, and perhaps the main goal, of balanced power is to minimize noise on the AC safety ground. AC safety ground is connected to the chassis of the component, and much of the noise injected onto the chassis will inevitably find its way to the circuit ground/signal ground of the component. In some components circuit ground and chassis are even connected directly together, and in many others they are connected together through a low impedance.

The component’s power transformer cannot help with respect to noise coupling through that path, because it is not in that path. And in fact it can itself contribute to coupling of power line noise onto the component’s grounds, via stray capacitances that will inevitably exist within it.

Also, btw, a major source of the noise that balanced power can help reduce will be the components themselves. See this paper for a somewhat simplified overview, and this one for greater detail.

On another note, glad to see you’ve made some progress with the problem being discussed in your other thread.

Regards,
-- Al

Great inputs from Ralph (Atmasphere), as usual.

Gbart, thanks also for calling attention to the papers presenting the many measurements. I haven't taken the time to read most of them yet, but FWIW I would suggest to those who do read them that whatever conclusions are reached by the author be carefully scrutinized, and not just accepted at face value. I say that because not long ago, in connection with a thread here on fuse directionality, I did thoroughly review Part 7 of those papers, relating to fuses. My comments on it were presented here.

Regards,
-- Al