Amp power cord question?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by retro, Jan 23, 2006.


  1. retro

    retro Member

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    I never really thought about this, until now...

    Is an 18/3 120v power cord adequate for a tube amp head?

    Or does one need something like a 16/3, or more?

    Seems like all the replacement cords I am finding for amps are 18/3 types. So I would assume they must be good, but....all the cords I ever had that came with an amp were heavier duty.

    Would someone be kind enough to provide the info for what is typically needed or correct for an amp?

    Thanks...
     
  2. bob-i

    bob-i Member

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    What amp head?

    Typically yes, that's fine.
     
  3. retro

    retro Member

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    Thanks Bob-i

    A Marshall JTM45. With a IEC type plug, rated at 117v, 175 watts.

    I know Mojotone is selling 18/3's and also Metropolis...and I know George knows his Marshall's.

    The thing that made me think about it is all the other amps I've had, have been more like16/3. Even the little Bronco. So I got curious and thought I should ask if there is a technical reason or advantage for having a heavier duty cord.
     
  4. Shea

    Shea Member

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  5. robbieboyette

    robbieboyette Member

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    You gotta be shittin' me!!! An $1800 power cord!!!!! What was it that PT Barnum once said? :NUTS
     
  6. retro

    retro Member

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  7. robbieboyette

    robbieboyette Member

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    :D LOL! The wooden knobs! I know audiophiles are notoriously insane...but that guy is selling some serious snake oil!
     
  8. Shea

    Shea Member

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    It has patented low molecular structure.

    Which is good, because nothing ruins tone like a power cord with too many molecules.

    Shea
     
  9. robbieboyette

    robbieboyette Member

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    Damn it! I was just drinking some iced tea and laughed so hard I spewed "molecules" out of my nose!!! :D
     
  10. Shea

    Shea Member

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  11. Rich M

    Rich M Member

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    Wait! You just can't plug a $1200 cord into any wall outlet. You need a "cryotreated" hubbell wall duplex:
    http://www.jenatek.com/pages/powercords.html
    A comparative bargain at $100. Anybody know where I can get some cryo treated Romex??
     
  12. trisonic

    trisonic Member

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    You don't even get 12 feet for your dosh - now, that really is outrageous!

    Best, Pete.
     
  13. robbieboyette

    robbieboyette Member

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    Hell, I'm thinking that "regular" old electricity from the power lines outside isn't gonna sound right either. I'm thinking there must be some kind of gold plated power generator that is completely shielded and only produces "clean" electricity. And of course it can't just run on plain old gasoline...it'll have to run on platinum. And yes...it was sweet tea!
     
  14. John Phillips

    John Phillips Member

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    [warning: potential controversy ;)]

    IMO a thicker cable could be worthwhile. Not expensive, just thicker.

    I don't believe any electrical cable has 'magic' audio properties, but it does have resistance, and it's just possible that the cable from the wall to the amp could be more significant than any other part of the supply chain. Yes, I know that there are dozens of feet of wiring in the house, and probably a mile or two back to the local transformer, but if you work out (based on its current rating) the relative resistance of the various cables, compared to a thin power cord, house wiring has about 1% of the resistance per unit length, and neighborhood supply overhead about 0.1% - so a six-foot amp power cord may have as much resistance as 600 feet of house wiring and 6,000 feet - more than a mile - of electricity company cable. The wire inside the amp from the fuseholder and/or switch to the transformer is fairly thin too, but it's short (a few inches), so it has less total resistance. But the difference between the thinnest normal power cord and the thickest is a current rating difference of just over three times, which means that a thick cable has about 1/10th of the resistance as a thin one, for the same length. This could be a fairly big proportional change in the total resistance between the neighborhood transformer and the amp's transformer.

    (I'm basing this on UK ratings of cable, BTW - which are given in cross-sectional area and current capacity, not AWG, and I don't know the exact equivalents in the US, but they must be broadly similar. The current rating is based on power dissipation from the cable, which is proportional to the square of the current through it times its resistance, so to handle ten times the current it must have 1/100th the resistance.)

    Does it make any difference to the sound? For low-powered amps, probably not, but for high-powered ones with greater variations in current draw when they're up loud, it might - I think I can hear a difference between a 3A and a 10A cable with my bass player's 250W amp. The total resistance is still less than an ohm, but it isn't zero, so I don't think you can conclusively say there's no effect.

    But the reason I made the big cable for that amp in the first place is because big thick cables are physically more robust for gig use :).
     
  15. Shea

    Shea Member

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    You jest, but that's the idea behind power conditioning. And I'm just going to stay out of that controversy.

    Of course! I lived in South Carolina in the 80s, so I know about sweet tea.

    Shea
     
  16. bob-i

    bob-i Member

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    18AWG can handle about 2.3A. Calculating the max on your amp it comes out to about 1.5. You have headroom so I'd it's a go.

    As for larger cords on this amp, yes there is some resistance in cords, like 20ohms/km. Moving to a 16AWG would drop that to 13ohms/km. Remember that there's wire in the wall and to the poles too so I'd doubt if you'll hear a difference.

    As for heavier cords on small amps, there's 2 reasons for that. One is durability, they're just harder to break when hendled roughly, and 2 is bulk purchasing/inventory, if you only stock one size it cuts costs.
     
  17. scottl

    scottl Member

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    My friend brought over his brothers crazy $300 audiophile power cable about a year ago. We a/b'ed using my 100 watt Fuchs head. It was cheapo 18 gauge versus crazy cable. The crazy cable sounded far deeper and clearer. Don't even start with the psycho-acoustic doubters bs. I did not buy the cable, nor have anything at stake. I actually was a big doubter. So, as a result, I now use a $5 14 gauge cable. Makes me feel good.... To be honest, I have not a/b'ed the 14 versus 18, but I feel I did something about it.

    Sunday at NAMM, I picked up a HOSA 15 foot 14 gauge power cable for $5. Why everyone would not want a longer and robust cable that very well may sound superior is beyond me.... Only $5.....
     
  18. retro

    retro Member

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    Thank you Bob-i and John for the info.

    It is appreciated.

    Good to know about Hosa as a source. I hadn't thought of them for power cords.

    Ah it's their PWC-400 series cords....

    PWC-415 is 15' and PWC-425 is 25', etc.

    Thanks...
     
  19. deeval

    deeval Supporting Member

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    First of all Always Check the polarity of the outlet you are plugged into as that would make a differance,and I always use a Furman VoltRegulator,and what a differance that makes,and only 300.00 and I can use with any Amp,without having to replace Power cords.
     

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