Why does better power = better sound?

Bryon,

Audio Grade Power Cords - AGPC

We investigated this interesting problem years ago and
found that the power cord(s) affect the 'ground-floor'
noise of the audio equipment being used.

The question is then how ?

By trying different home made power cords we could hear
differences in the music we listened to. We then made up
high impedance probe to see if there was any noise on the
power cords. The spectrum analyzer showed that there was noise
from 8 MHz to 13 MHz. We tested other power amps and cd-players
and found this same 'noise' on all tranformer power supplies.

This lead us to reconsider the power system', which is the wall socket,
the power cord and the equipment's power transformer.

Intuitively we all know that the wall socket's impedance/resistamce
is different from the power transformer's impedance/resistance.

So we decided to measure the wall sockets 'resistance'.

By using a salt-water-bath-load [old RF trick] we came up with the following
information: [see our AGPC white-paper for more details]

1.) Copper wire feed sockets have about .23 Ohms of impedance
2.) Aluminum wire feed sockets are about .45 Ohms of impedance.

This give us the source 'resistance'.

A power transformer 'resistance' that we used ranged from
11 Ohms to 14 Ohms. The ratio of the source with the transformer
is then from 50 to 58 to 1. This SWR of 50-58 at full wave lenght
would have a 90% reflection level.

The concurrent argument is that the power cord is too short !

Very true; compared to the miles at 60 Hz / 6 feet is very
insignificant,- almost-.

Looking at the power applied we know it is 60 cycles per second
or 120 pulses per second. The measured nosie is in the low MHz
range. Looking at the harmonic relationship of the 60/120 cycle/pulse
with the noise frequency we can see that they are related.
From 3MHz to about 30 MHz the pulsing energy is:[examples]
3 MHz : 60Hz 50k-1; 120pps 25k-1
12 MHz : 60Hz 200k-1; 120pps 100k-1
and are evenly harmonically related with the 'measured' 'noise'.

Then the next step is to determine how much noise is 'generated'
from this resistive mis-match.

By looking again at the spectrum analayzer we can see how much
noise-energy is being produced.

The graph on the analyzer showed a range of 250 - 375 mVs of noise.

Now what, how does this affect the audio signal.

This nosie is of very high frequncy energy and should be filterd easily
by the power supplies. But remember the low-side the -white-wire- of
the power cord and the -green- ground wire are tied to the equipment's
low side!

The Hot-wire and nosie are in a long-shaped 'capacitor' with the
white and green wire; the nosie can easily pass through this natural
'capacitor' since the 'noise' is of very high frequency.

The 'ground-plane' then has extra 'energy' of high frequencies that can
pass onto the solid state parts of the audio systems.
Transistor's control volatages are from about .4 v to .66 v and this low
level of voltages can easily be affected by this high 'Frequncy-Noise'.

With this information we can see why the CD-player is far more likely to be
affected by the 'power cord' than the power amplifier.

The power cord itself has an affect on the nose being generated due to
the changes in the differnt 'materials' used in their consruction.

- - -

Well hope this information will lead to better Fidelity!

Interesting post, Cjl; thanks!

The one issue I have with your analysis, though, is that it seems to imply that if the impedance looking back into the wall outlet matched the impedance looking into the AC input of the component, the high frequency noise you measured would not cause a problem, and (if I interpreted correctly) might not have been generated in the first place.

As you probably realize, RF reflections occur at each end of a transmission line, in response to arriving energy, as a result of a mismatch between the characteristic impedance of the transmission line and the impedance of what is connected at that end of the line. In the case of most or all power cords, characteristic impedance is undefined, poorly controlled, and very unlikely to match the impedance of either of the things it is connected to, at any given frequency. So RF reflections will occur regardless of the relation between the source and load impedances.

Also, it seems to me that reflections of noise frequencies are not necessarily bad in this situation. If a gross impedance mismatch at the AC input of the component causes incoming noise energy to reflect back toward the outlet, and re-reflections from the outlet to re-re-reflect from the component back toward the outlet, back and forth essentially ad infinitum (the energy gradually being dissipated in the power cord), that would seem preferable to the situation in which a perfect impedance match between the power cord and the component results in that energy being absorbed into the component.

Regards,
-- Al

My experience with cd players is that the further away you isolate them from your other gear the better your sound will be.

I have found that plugging the CD player all by itself into a Furman 15 amp balanced power conditioner sounds better than plugging it into the Hydra 8 and then into the Furman.

I plug my turntable and phono/pre into the Hydra 8 and then into the Furman, which goes into one half of a Shunyata power receptacle on a dedicated 20 amp line.

The other half of the receptacle feeds a hydra 2 to the tube mono servo amps that power the Acoustats.

I use Annaconada's all around, and HiFi supreme fuses.

I also use copper foil at all cable connections and blue tack to add some resonant damping at all electrical connections.

I would really like to try the Audience gear, or for that matter the PS power plant 5.

The power in my area is awful, 110 most of the time, and I'm 10 minutes from Niagara Falls !.

IMOP all power lines are outdated and long overdue for a makeover.

Perhaps things are just fine out in the sticks and the power is still pure, like the air, but I wouldn't bet on it.

I don't think there is a system around that wouldn't benefit from doing something to improve the power, no matter how elaborate or costly the system is or how good you think it is.

It is only as good as the power going to it.
Your gear is the slave to the power which is the master.

It doesn't work the other way around,no matter how great you think your gear is made.

Not only is there reflection noise and variable voltage/frequency, but power companies often send data through the power lines as well. There is a pile of noise on the line. Digital components tend to spew significant noise back into the power supply as well, particularly on the ground.
Now unless you are running a floating balanced output stage in your power amp your speakers are connected directly to the main grid on the negative side. The negative speaker terminal in your power amp is on the wall side of the mains transformer. The power amplifier is merely modulating the main power grid supply.
With regard to power cables, if your power lines are run in a loop through the house, then a power cable is seen as a a spur off that loop. My understanding is that if a power cable is too short then the pc will behave as if it is part of the loop, whereas if it is say 2m or more it will behave as a spur. There is a difference.

Dover, thanks for your comment.

I don't mean to be picky, but I think it would be better to refer to "reflected noise," rather than "reflection noise." The reason I make a point of saying that is that Cjl's post seemed to say that reflections caused by impedance mismatches PRODUCE noise, which is simply untrue. Reflections of noise frequencies that may be present can ALTER the effects of that noise on the system, although with little or no predictability. But impedance mismatches do not produce noise, and reflections do not occur unless there is something to reflect.

Now unless you are running a floating balanced output stage in your power amp your speakers are connected directly to the main grid on the negative side. The negative speaker terminal in your power amp is on the wall side of the mains transformer.

The negative speaker terminal will usually be connected to AC safety ground (and the amplifier chassis) through a low impedance, such as a low value resistor, or in some cases directly. The paths between AC safety ground and the primary side of the power transformer, in turn, will be via stray capacitance, especially within the transformer, and via the connection that exists between AC safety ground and AC neutral back at the electrical service panel.

In any event, the speaker will only respond to the instantaneous voltage DIFFERENCE that exists between the + and - output terminals of the amplifier. The noise levels that may be present in that difference, as a result of noise on the incoming AC, will be VASTLY lower than the noise on the incoming AC, assuming that the amplifier design is half-way decent. And the speaker, as well as our ears, will not be capable of responding to RF and digital noise frequencies anyway. The possible sonic consequences of high frequency noise on the AC line would result from intermodulation and other effects occurring in internal amplifier circuitry, that may end up affecting audible frequencies.

My understanding is that if a power cable is too short then the pc will behave as if it is part of the loop, whereas if it is say 2m or more it will behave as a spur. There is a difference.

There is no hard and fast dividing line. It depends on the frequency of each particular frequency component of the particular noise that is present, and (to a lesser degree) on the propagation velocity of the particular wiring. For the very high 8 to 13 MHz noise frequencies that were among those Cjl referred to, 2 meters is a reasonable rough rule-of-thumb approximation. Noise frequencies that are much lower would require a much longer cable length to behave as a spur.

Again, thanks for your comment, and my intention in responding is not to be picayune, and (as my earlier posts make clear) is not to deny that power cords can make a difference.

Best regards,
-- Al