Close spacing is the key to low inductance. Twisting two conductors together causes then to be in intimate contact over the length and therefore will result in lower inductance. Parallel wires, if in tight contact will also have low inductance. It is just easier to twist them to get the close spacing. ROMEX has a large spacing between the conductors and therefore has high-inductance. I have a table on my website that compares the inductance of ROMEX and various cords. See the Power Cable page at:
http://www.empiricalaudio.com
BTW, the best construction is to use solid 12 gauge THHN wire twisting the hot and neutral together and then twist the ground around them in the opposite direction. Put this inside a plastic conduit to meet code. |
Ozfly:
One of the electrical engineers who frequent our site may shoot me down on this, but I honestly don't think it will make any difference -- from an audibility standpoint -- whether you run twisted or parallel power cords from the panel to the outlet. Please note that I am not saying that there aren't valid electrical transmission issues that should be considered -- only that they should not be audible.
The electric current that will be coming out of the wall precedes any signal, and the AC power is going to be reduced in voltage by the transformer in your power amp, and then rectified from AC to DC current. Hence, concerns like inductance and capacitance should not be of any concern with your house wiring. Once the audio signal leaves the amp on its way to the speakers, however, the behavior of the speaker wiring with regard to capacitance, inductance, and characteristic impedance can be a real issue, which is one of the reasons there are so many approaches to speaker cable design. |
Audioengr, Nice to see your page! What is the overall inductance impact on 12AWG 2m power wire that passes 60Hz from the wall?
X(reactance) = sqrt(2*pi*60Hz*L)
In this formula L is in microHenries range and reactance on 60Hz is just tens of miliohms so the voltage drop due to inductance is realy measurable. The AC deviations are much higher than the voltage drop due to the inductance isn't it?
After all how the low-inductive power cord will be different from high-inductive one if the bottom line is that the signal is being rectified and decreased and sometimes internally stabilized.
What anywhay the good quality power cord can do except reducing the noise, microphonics and AC impact? |
Without even questioning the scientific reasoning & recommendations of cable designer Mike VansEvers I went with the twisted 10awg THHN solid copper, installed in grounded Greenfield (flexible metal conduit) for shielding. This works so well that I haven't even bothered to try out anything else so I can't actually compare, but can attest to my own very satisfactory results.
Mike told me to tape all 3 conductors together, then clamp one end of the bundle in a vice & the other end in a variable speed drill chuck. I aligned the printing on all 3 conductors in the same direction before twisting them up. It winds up like a big spring & then unwinds somewhat when the drill is powered off, so I then exchanged ends & better re-twisted the remainder. The load end is now terminated with a Wattagate 381 outlet, which from a sonic standpoint completely obliterated the 20A industrial Leviton outlet that was previously in place. |
And don't forget the Isolated ground rod (Star configuration of course), ceramic fuse box with glass fuses, I.G recptacles (Hospital grade minimum) Isolation transformer, Isolated generator, Isolated sub panel (with oversized feeders) U.P.S. battery backup, Oversized neutral, oversized ground, isolated ground, dirty ground, dedicated neutral, #6 copper wire (Beldon shielded cable) Industrial grade 3 phase service with bolt on breakers. Twenty seven dedicated 120 volt circuits and three ninty amp 240 volt circuits (just in case)
Did I miss anything? :^) |
no - never use glass fuses they sound terrible.
Ceramic is the only way to go, but I have a feeling Glen that you don't subscribe to any of this nonsense. Well neither did I, until I heard it for myself. I'll never go back. |
Actually Bob I do subscribe to some of it :^) |
Ozfly, increased inductance on a power cord has its' ups and downs. As inductance is increased, you obtain a natural amount of high frequency roll-off. Kind of like a "low pass filter" that lets the low frequencies "pass through" and attenuates "hash" somewhere above that point. Obviously, the amount of attenuation, cut-off frequency and rate that it slopes off at will vary with the total amount of inductance for the entire run of wire.
While this may be a good thing for power cords due to their limited bandwidth, it is obviously not so good for speaker cables or interconnects. That is why most of the "high end" cable designs are of limited inductance. It should be pointed out that the "roll-off" of an inductive cable can be put to good use if you have an overly bright system. That is walking a tight-rope though, as too much inductance will dull the system out and not enough will still leave you with too much brightness. Better to fix the problem than try to band-aid it. Sometimes though, band-aids are all one can afford at that specific time : )
As to the bad part, wires that are higher in inductance act as a more efficient antenna to RF based signals. It is easier to "induce" stray voltage into them. Obviously, this can be a bad thing if you live in a densely populated area with a lot of transmitters ( cell and cordless phones, AM / FM / TV broadcast stations, CB's, Ham Radio's, etc... ).
The method that Audioengr suggests should theoretically offer benefits over some of the other methods mentioned. However, it would be a lot more work than what Bob suggested and tough to predict whether the results would be worth the extra effort under real world conditions. If one were interested in putting forth that much effort, there are ways to achieve even better results. I don't want to go into details here for specific reasons though : ) Once again though, whether the results would be actually audible or simply more "icing on the cake / increased peace of mind" would be anyone's guess.
If one wanted to get REALLY serious, they could actually measure the total impedance of the run, break down the measurements into specific LCR ( L = inductance, C = capacitance, R = resistance ) characteristics and then create a tuned trap or bandpass filter by adding additonal parts. Something like that would not really suffer from current limitations ( if done properly ) and would benefit everything plugged into that line. Obviously, this would be the optimum way to go but also ( by far ) the most involved.
The bottom line on all of this would simply be a "blacker background" and "increased liquidity" from my experience. Sean
> |
Glen,
You forgot the 27 vestal virgins singing the Benjamin Britten "Hymn to the Sacred Electrical Particles."
Incense will help, too. I've had good results with pure gum frankincense, although the addition of a bit of myrrh can help to tame a hot tweeter.
Let's smile, folks. I respect those who believe with all their hearts that these things make a difference and I respect those who think it is all blue smoke and mirrors. What a pity they so seldom respect each other....
will |
Thanks all. I'll go with the 27 vestal virgins approach. In lieu of that, the twisted 10 gauge in conduit seems like a plan. Not too expensive and likely to gain good results. Thanks again.
P.S. Per suggestions in earlier posts and above, I will be using the "star" pattern in that all grounds will first go directly to a separate ground rod (next to the one for the house) and then be tied together at the box to avoid ground loop noise. A preferred ground "star" approach. Thanks. |
Marakanetz - The di/dt currents in the power cord are what matters. IF it is too inductive, the drops can be in the Volts, not mVolts. I have one of the lowest inductance cords on the market and it is getting rave reviews when used with power amps. If you read my description on my poer-cord page, it describes how the voltage drops can occur. Poor power cords can have the same effect that plugging into multiple power strips has, except on transients. If your amplifier has switching supply, the impact of a low-inductance power cord may be much less, because of the regulation.
BTW - twisting the two current-carrying wires has the additional benefit of radiating a smaller magnetic field that can impinge on nearby interconnects compared to two parallel wires. |
Your delight is appreciated, Audioengr. Thanks! |
Thanks Will, I completly forgot about the Virgins :^)
Just as long as your having fun and not burning down the house it really doesn't matter what you do IMO.
I ran six dedicated circuits to start and am now kicking myself I didn't run ten. There's just something about isolating every component, sub woofer and powered woofer section that really turns me on, and this time I'm being serious
The noise floor dropped dramatically with three circuits to two seperate systems. I can't help but wonder how much lower it can go. |
This thread just keeps on getting better & better. Wow; 6 to 10 times the work that I had to do for my single dedicated line; is it really 6 to 10 times quieter? Could certainly be, but I really don't think I want to get that involved in this scenario. Have at it; whatever floats your boat is fine with me too.
Oz: I didn't mention above (I'm just not THAT into it) that some have found wire directionality to be a sonic issue, just as in audio cabling. That why I suggest aligning the printing on the insulation with all wires running the same way. I didn't try this myself, but some have temp'd in the wiring, listened for a day, then turned the whole thing around in the opposite direction & listened again. Hard to believe I know, but the results were that one direction sounded better than the other direction. By the time I had read about this, my own ded. line was already weeks old so I figured it was pretty much broken in & would only sound worse if turned around so I didn't bother with that test. Of course YMMV. |
Bob,
It's really not that much more labor to run three circuits as opposed to one. I ran the circuits in 3/4" pipe (One to each location). Then pulled the wire, made up the devices, terminated the breakers, test the system and BINGO WE HAVE A WINNER! I actually have room in the conduits to pull more circuits but that sounds to much LIKE WORK!!! |
This is really the way to do it. It keeps the grounds pretty much at the same potential and the lengths of each conductor about the same. Ground-loops is the biggest concern when running multiple circuits. |
Audioengr,
I've surfed through your website recently.
You've got a huge amount of talk about skin effect.
Can you remind the formula calculating the current density? I want to apply it for audiable freeqencies and see the range of impedance changes.
Thanks! |
