Amplifier hum... loud!!

Lowell_M
Lowell_M Posts: 1,660
edited January 2009 in Electronics
I am demoing DGK999's Marsh A200s amp this weekend and first hooked it up yesterday. All I did was take my ADCOM amp out of the rack and replaced it with the Marsh with the same IC's, etc. When I powered on the amp, both channels hummed at an uncomfortable level.

If I used a cheater plug from the outlet so that the ground wasn't connected, the hum went away.

I tried to search about this and couldn't find anything and it has happened before at our local get togethers, but I thought I would see what others have to say. What the hell is going on here?

The amp sounds freaking sweet, by the way, after you get rid of the hum.
HT
RTi70 mains
CSi30 center
RTi28 Rears
Velodyne CHT-12
H/K AVR-247
ADCOM GFA-7000
Samsung PN58B860
Playstation 3
2-Channel
Polk Audio LSi15's
Rotel RCD-1072
Nakamichi CA-5 Pre
ADCOM GFA-555
Signal Cable Analog II IC's
Signal Ultra Bi-Wire Speaker Cables
Post edited by Lowell_M on
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Comments

  • strider
    strider Posts: 2,568
    edited January 2009
    Sounds like a typical ground loop hum. I'm not certain if there's a downside to using a cheater plug or not, but I've been doing the same thing with my amp for years.
    Wristwatch--->Crisco
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  • Lowell_M
    Lowell_M Posts: 1,660
    edited January 2009
    Yea... finally found some ground loop hum info thanks to FACE. Why would I have the problem with the Marsh and not my ADCOM? Wait a minute!!!!!!!!! let me look at something.... There's no ground on the ADCOM power cord!!

    Sorry for the waste of a thread. Problem solved.
    HT
    RTi70 mains
    CSi30 center
    RTi28 Rears
    Velodyne CHT-12
    H/K AVR-247
    ADCOM GFA-7000
    Samsung PN58B860
    Playstation 3
    2-Channel
    Polk Audio LSi15's
    Rotel RCD-1072
    Nakamichi CA-5 Pre
    ADCOM GFA-555
    Signal Cable Analog II IC's
    Signal Ultra Bi-Wire Speaker Cables
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  • MillerLiteScott
    MillerLiteScott Posts: 2,564
    edited January 2009
    Does the Marsh have a ground lug on the back? I have a ground lug on the back of my cd player, integrated, power conditioner and turntable. I have all of them connected to one isolated point. It got rid of the hum I was getting when I played my turntable. Worth a try. Prior to this I had a hum from my CD player and I broke the ground prong off of the plug after I figured out that was my problem by using a cheater plug. YMMV.

    Scott
    I like speakers that are bigger than a small refrigerator but smaller than a big refrigerator:D
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  • ShinAce
    ShinAce Posts: 1,194
    edited January 2009
    This is why old equipment had the 'ground' screw on the back so you could tie equipment together and get rid of hums.

    It has little to do with 2 prong vs 3 prong and more to do with how the equipment is designed. It's possible that a balanced signal wouldn't have this problem, but I haven't taken the time to think it through.
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  • snow
    snow Posts: 4,344
    edited January 2009
    ShinAce wrote: »
    This is why old equipment had the 'ground' screw on the back so you could tie equipment together and get rid of hums.

    It has little to do with 2 prong vs 3 prong and more to do with how the equipment is designed. It's possible that a balanced signal wouldn't have this problem, but I haven't taken the time to think it through.
    Yes if you are using balanced in's and out's you wont have the hum.



    REGARDS SNOW
    Well, I just pulled off the impossible by doing a double-blind comparison all by myself, purely by virtue of the fact that I completely and stupidly forgot what I did last. I guess that getting old does have its advantages after all :D
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