Why does better power = better sound?


Why does improving power quality improve sound quality?

I’m not asking to start an argument about power cords or wall outlets. Please let’s not go there. I’m asking because I’m hoping to learn some technical explanations for the effects of power quality on sound quality. I think I already understand how…

1. greater current availability = greater dynamic range
2. reduction of RFI/EMI = better signal to noise ratio

…but what about these…

3. ???????? = greater perceived resolution
4. ???????? = more realistic instrument timbres
5. ???????? = more precise imaging

Are differences in resolution, instrument timbres, imaging, etc. somehow reducible to current availability and/or powerline noise? If so, HOW are they reducible?

Again, I’m hoping to get into technical specifics, not polemical generalities.

Thanks in advance.

Bryon
bryoncunningham
Al and Kijanki, assuming I go forward with installing 3 or 4 dedicated lines, will I need a power conditioner for each line? Just talking out loud here, I wonder if there's a single device that I can install at the circuit box that will condition and filter the AC power for multiple dedicated lines.
Hi Bruce,

I have no particular knowledge of an audio-oriented conditioner that would handle multiple lines at the panel. But in any event I would expect that installing conditioners at the system end of the runs would be preferable, because they would then be able to filter out RFI that may be picked up by the wiring between the panel and the outlets.

It would probably make sense to purchase one conditioner initially, and try it out on each of the different lines.

Not familiar with the Gardner "Pastorale"; thanks for mentioning it. My "go to" version is an imported Japanese CBS/Sony remastering, on LP, of Bruno Walter's famous 1958(!) performance with the Columbia Symphony. I purchased it during the 1980's. Wonderful performance, of course, and remarkably pleasing sonics aside from a bit of steeliness in the strings at times.

Best regards,
-- Al
Thanks to everyone. Some very helpful comments.

I understand that the DC power provided by a component’s power supply is the same power that constitutes the component’s signal, and that therefore noise or distortion on the AC power line, if insufficiently filtered by the component's power supply, will become part of the signal.

What I’m unclear about is how SPECIFIC audible characteristics correlate with SPECIFIC AC/DC powerline anomalies. Put simply, HOW does bad power result in bad timbre, or bad imaging, or less resolution, etc.?

04-24-12: Almarg
…any and all of those numerous frequency components could, to some small extent, intermodulate with the audio signal, resulting in new spectral components at frequencies equal to both the sum of and the difference between the frequencies of any or all of the spectral components of the music and the frequencies of any or all of the spectral components of the noise or distortion.

This was extremely helpful, Al. I wasn’t really thinking in terms of frequency intermodulation, but when I do, it’s easier for me to understand how bad power results in less realistic instrument timbres. It's something like...

AC power frequency anomalies -> DC power anomalies -> INTERMODULATION of DC power and signal -> distortion of harmonic content -> less realistic instrument timbres

Because accurate harmonic content is essential to realistic instrument timbres, anything that distorts harmonic content, like the intermodulation of DC power and signal, will make instrument timbres less realistic. Sounds plausible to me.

So filling in the question marks to #3 in the OP is…

3. dc power/signal frequency intermodulation = less realistic instrument timbre

Assuming all this is correct, I’m still unclear about the explanation at the level of voltage and current. In particular, I'm unclear about the concept of "frequency intermodulation" with respect to DC power. Some dumb questions...

--Does "frequency intermodulation" basically mean that there are FLUCTUATIONS to DC voltage/current that are UNRELATED to the signal?

--Why are DC fluctuations described in terms of "frequencies" at all? Is it simply because the fluctuations occur at a certain rate per second? Or does the use of "frequency" to describe fluctuations in DC voltage/current also imply that DC can be understood as a WAVE, just like AC?

I have lots of additional thoughts/questions about resolution and imaging, but it would be helpful to stick to instrument timbres for the moment, or my head might explode.

Thanks,
Bryon
Hi Bryon,

The effects I was describing do not necessarily relate to the DC outputs of the power supply at all. There are many possible pathways by which spurious frequency components riding on the incoming AC may couple into the signal path. To the extent that the filtering in the power supply is not perfect at all frequencies, the spurious frequency components may couple into the signal path by "riding" on the DC outputs of the supply. Some of those spurious frequency components may instead completely bypass the power supply, and couple into the signal path through stray capacitances that will inevitably exist in a great many places in the circuitry, or they may couple into the signal path via EMI effects, or they may radiate into the signal path as RFI.

Once the signal, at any given point in the signal path, combines with spurious frequency components that may be picked up at that point via any of those pathways, non-linearities in circuitry that is downstream of that point will result in the spurious sum and difference frequencies I referred to. See this Wikipedia writeup on Intermodulation Distortion.

To answer your specific questions:
Does "frequency intermodulation" basically mean that there are FLUCTUATIONS to DC voltage/current that are UNRELATED to the signal?
If the pathway by which AC line spurii enter the signal path is via the DC outputs of the power supply, then yes, there would be fluctuations in those DC voltages, unrelated to the signal. The value of those voltages at any instant of time would be equal to the numerical sum of the DC voltage and the value at that same instant of time of the fluctuating noise voltage that is riding on it.

However, that is not what is significant. What is significant is the noise coupling onto the signal, and subsequently intermodulating with it at downstream circuit points.
Why are DC fluctuations described in terms of "frequencies" at all? Is it simply because the fluctuations occur at a certain rate per second? Or does the use of "frequency" to describe fluctuations in DC voltage/current also imply that DC can be understood as a WAVE, just like AC?
When DC is fluctuating as a result of noise that is riding on it, it can be viewed as having multiple frequency components that are added together. One component, the DC itself, is at a frequency of zero Hertz and has an amplitude equal to the particular DC voltage. Other components will be present at each of the many frequencies that comprise the noise, with the frequency components of the noise having far smaller amplitudes than the amplitude of the DC. The net voltage at any instant of time will be the numerical sum of the individual amplitudes (voltages) of each frequency component at that instant of time.

The DC (zero Hertz) component of the combination of DC + noise has no relevance to the sonic effects we are discussing; it is just a possible pathway by which the noise may combine with the signal.

Best,
-- Al
There are many possible pathways by which spurious frequency components riding on the incoming AC may couple into the signal path... Some of those spurious frequency components may instead completely bypass the power supply, and couple into the signal path through stray capacitances that will inevitably exist in a great many places in the circuitry, or they may couple into the signal path via EMI effects, or they may radiate into the signal path as RFI.
Got it. In my last post, I was just trying to limit things as much as possible to a single scenario, so my brain doesn't hurt too much. :-) But I understand that spurii may originate from other sources, like EMI, RFI, stray capacitance, etc..

What particularly confused me was the concept of "frequency intermodulation," -- not so much the "intermodulation" part, but rather the "frequency" part, in light of the fact that we're talking about DC. My naive reasoning goes, "If DC is zero Hertz, then how does DC have a frequency to be intermodulated?" My (admittedly limited) understanding of "frequency intermodulation" is that it results in frequency components that are both the SUM AND DIFFERENCE of the original frequencies. So although I think I understand your comment that...
The net voltage at any instant of time will be the NUMERICAL SUM of the individual amplitudes (voltages) of each frequency component at that instant of time.
...but what about the DIFFERENCE part of intermodulation?

Wait a second. Maybe I just figured it out. (I'm typing as I'm thinking)

I was thinking that the "frequency intermodulation" you've been describing was some kind of intermodulation of the DC VOLTAGE with the NOISE. In other words...

IM = [DC voltage + noise] & [DC voltage - noise]

But maybe you've been talking about the intermodulation of the COMBINED DC VOLTAGE/NOISE with the SIGNAL. So...

IM = ([DC voltage + noise] + signal) & ([DC voltage + noise] - signal)

And maybe THAT is what you meant when you said...
The DC (zero Hertz) component of the combination of DC + noise has no relevance to the sonic effects we are discussing; it is just a possible pathway by which the noise may combine with the signal.

Am I anywhere closer to understanding this, or is it hopeless?

Bryon