Wall Outlet Oyaide, Furutek, Wattgate, and others

Hi Dave,

To answer your questions clearly, I should probably first state that “60 Hz AC power" consists of a vast number of different frequency components. The highest amplitude/biggest of them is the 60 Hz component, of course. But there are also components at much higher frequencies corresponding to the brief high current spikes you mentioned earlier, probably extending up to tens of kHz, particularly in the case of power amplifiers. And there are frequency components at integral multiples of 60 Hz (i.e., 120 Hz, 180 Hz, 240 Hz, etc.) corresponding to harmonic distortion that will be present in the waveform to some degree. And there are essentially an infinite number of low level frequency components corresponding to noise, extending up into the RF region.

In answer to your questions, yes, strictly speaking a “resistance” at any frequency other than zero Hz (i.e., DC) should be referred to as “impedance,” which reflects a combination of resistance, inductance, and capacitance. And, yes, resistance in series will add to impedance.

In a local (in-house) power distribution system, however, impedance at 60 Hz will be dominated by resistance. Inductance and capacitance will become more significant at the frequencies of the much higher frequency components of the AC waveform. But I would not expect the inductance and capacitance of an outlet to have a great deal of significance in relation to the inductance and capacitance of the power cords and the house wiring. Everything else being equal, the inductance, capacitance, and resistance of conductors are proportional to length (although of course everything else is rarely precisely equal).

In answer to your last question, the impedance of the power delivery system should be low, at least at frequencies up to and somewhat beyond the frequency components corresponding to the brief high current spikes that have been mentioned. (Series impedance that is high at frequencies greater than that may be helpful in reducing noise, but I would not expect an outlet to play much of a role in that regard).

**HOWEVER**, for any design parameter that should be low there exists a point beyond which further minimization will:

1)Be overkill, that increases cost but accomplishes nothing, and/or

2)Be negligible in relation to the contributions of other things in the path that also contribute to the parameter, and/or

3)Be accomplished at the expense of other parameters that may be significant.

The basic point to my previous post was to provide a quantitative perspective on the differences in resistance that were cited in the reference you provided. Consistent with my comments above and in that post, I believe that if in fact there are differences in the behavior of those outlets that are audibly perceptible to some listeners in some systems, the differences in resistance that were indicated in the reference are very unlikely to be the reason. And even if there is a difference and resistance is the reason, the difference could work in either direction (good or bad), depending on the happenstance of the line voltage at the particular location and on the design of the particular components.

Regarding your mention of matching of metallurgy, that is outside of my areas of expertise and I have no particular comments.

Regards,

-- Al

Nice!, Very good post gentleman, I enjoy learning from both of you Dave and AL, cheers.

Hello Al ... thanks for your enlightenment and how do you get your posts up so quick ... mine seem to take forever ..

I couldn’t agree more with both your posts about a point of diminishing returns and how going to far can be detrimental ... also at certain levels things can be insignificant and irrelevant

I seemed to have gotten off course when I received a poke in the eye with a sharp stick over my comment

The most important thing in your power delivery system is “low series resistance

It appears you support this point with your comment

In a local (in-house) power distribution system, however, impedance at 60 Hz will be dominated by resistance. Inductance and capacitance will become more significant at the frequencies of the much higher frequency components of the AC waveform

I never meant to imply that L and C were irrelevant ... only that R was more of a concern when looking at all 3 ... the reason being is rising series resistance would also increase Impedance

And, yes, resistance in series will add to impedance.

And the last piece of the puzzle is high or low Impedance ...

In answer to your last question, the impedance of the power delivery system should be low,

The enemy of my enemy is my friend ... Sun Tzu ... doesn’t inductance act as a low pass filter allowing low frequencies to pass while presenting a rising Impedance to frequencies as they rise ... I think that’s what you are saying

at least at frequencies up to and somewhat beyond the frequency components corresponding to the brief high current spikes that have been mentioned. (Series impedance that is high at frequencies greater than that may be helpful in reducing noise, but I would not expect an outlet to play much of a role in that regard).

OK so the outlet may not play a significant role in reducing RF.. but isn’t the Inductance of the cabling our friend in helping defeat some RF ?

My comments' are much more theory based to try and understand which direction things move in and their possible effects where as you’ve run the numbers and can speak from a practical stand point of the value of those numbers ... but it seems we agree

Increase series resistance will raise impedance and we would prefer to have a deliver system with a low Impedance

Now I would like to share some incite with you ....

If you want to teach your grandchildren about taxes ... eat 30 percent of their Ice Cream (;-

Best Dave

Hi Dave,

Yes, I think we are pretty much in agreement at this point. Apologies if some of my comments came across as a poke in the eye; that certainly wasn't my intent.

I would emphasize that since the contribution to impedance that is caused by inductance ("inductive reactance," which is measured in ohms) is directly proportional to frequency, and increased inductance in the power wiring may therefore be helpful to some degree with respect to reduction of high frequency noise, that potential benefit may trade off against the ability of the power wiring to quickly respond to abrupt changes in demand for current. Such as the brief high current spikes we have referred to, which as I indicated may contain significant frequency components up to tens of kHz, or perhaps even more in some circumstances.

I would expect that concern to generally be greatest in the case of power amplifiers or integrated amplifiers whose output stages operate in Class AB or Class D, for which AC current demand fluctuates widely with the dynamics of the music.

Regarding the first question in your last post, I can't provide a knowledgeable answer.

Good one re taxes :-)

Best regards,
-- Al

Hey, If this thread becomes TOO "reasonable" I'll have to stop following it. How about some good old fashioned vitriol, recrimination and name calling? Are we becoming genteel in our old age?