Why does better power = better sound?

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

I know this may be just hype from Burson Audio but they are big on power regulation and use only their own proprietary design, claiming it has a major effect on how the music sounds. Anything more involved is way above my head.

I do know, and appreciate, the results I get (from my Burson PI-160) which mirror what Bryon asks about.
Oh, and I use a Brickwall surge protector as well as it appears to have no negative effect on my music while deploying minimal filtering and maximum protection.

Either that or I'm tone deaf.

Since we're also discussing power line accessories, I'll share what I've done...

--Dedicated 20 amp line with VH Audio's Cryo'd 10 gauge Romex. I routed it myself to minimize distance and to avoid crossing any other AC power lines.
--Shunyata Hydra 8 power conditioner (for preamp, amp)
--PS Audio Duet power conditioner (for computer)
--3 Shunyata Python power cords (hydra, preamp, amp)
--5 PS Audio power cords (everything else)
--Outlets: Shunyata, Synergistic Research, PS Audio, Maestro (winner: Maestro).
--Preamp: custom power supply w/ Rubycon capacitors, custom rectifier, SMD ultra fast diodes
--Preamp: removed IEC filter
--Preamp: replaced internal wiring to power supply with DH Labs 14 gauge silver plated wire
--Preamp: shielded power supply w/ copper, steel, and TI Shield
--Silver Hifi Tuning Fuses for preamp and amp
--6 Highwire Powerwraps on various power cords
--About 70 (!) ferrites all over the house wiring, on all appliances and electronics outside the audio system, and on some devices within the system
--Fairly extensive experimentation with grounding schemes, as described here

I haven't had a manic episode in several months, in case you were concerned.

One of the results of all that insanity is that things sound a lot better: Lower noise, more headroom, more resolution, more realistic timbres, better imaging. Now I'd like to know why the things I've done to address power have resulted in those specific improvements. The conversation about intermodulation is a pretty good explanation of how better power can result in better instrument timbres, in my underinformed opinion.

Maybe I can extrapolate explanations for headroom, noise, resolution, and imaging, though I have to confess a certain amount of mental murkiness. I have a weird thing where I feel like I don't understand something unless I understand it at its lowest level of explanation, which in this case is the level of FLOWING ELECTRONS.

(I know it gets lower, but hopefully we can avoid using the word 'quantum').

Bryon

Hi Bryon,

You're not there yet, but it is by no means hopeless :-)

My statement 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

had nothing to do with intermodulation distortion, or with the sum and difference frequencies that intermodulation distortion results in. It was simply a description of the voltage at any instant of time of DC that is noisy.

As long as they are reasonably small, fluctuations in the DC voltages will IN THEMSELVES have no effect on anything. It is only when the frequency components corresponding to those fluctuations combine with the signal that a problem arises. The DC will not combine with the signal (in a properly functioning circuit). But the noise frequencies might, because they can couple from one circuit point to another via the various means I described.

Envision a musical note consisting of a 1 kHz fundamental frequency, and a harmonic of lesser amplitude at 9 kHz. (A real musical note would contain many other harmonics as well, such as 2 kHz, 3 kHz, etc. but I'm simplifying). And imagine that a noise frequency of 11 kHz, having some small but significant amplitude, couples onto that signal.

So far all that has happened is that a small 11 kHz signal has been added on to the signal having 1 and 9 kHz frequency components. That is probably not a major issue, assuming that the amplitude of the 11 kHz is not too great.

Now envision that the signal containing those three frequency components is passed through an amplification stage that has some degree of non-linearity, meaning that its output is not perfectly proportional to its input. Intermodulation caused by that non-linearity will result in many new frequencies, corresponding to the sums and differences between those three frequencies, and various other multiples of them. Perhaps most significantly, a 2 kHz frequency will be created as a result of intermodulation of the 9 and 11 kHz components. (20 kHz will also be created, among other new high frequencies, but that is obviously less significant). To the extent that the amplitude of that 2 kHz frequency is significant, it will alter the perceived timbre.

Now envision that a real-world musical note is present, consisting of a great many frequency components, and that noise also present, consisting of vastly more frequency components. Put all of that through a significant non-linearity and what you have is an unpredictable mess, having sonic attributes that can probably differ from those of the original signal in just about any way that is imaginable, including resolution, timbre, and imaging.

Best,
-- Al