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Thread: Ground loop between pre-amp and power amp?

  1. #21
    Join Date: Apr 2013

    Location: Granes - Haut Vallee de l'aude - EU

    Posts: 2,831
    I'm Richard.

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    Bottom left hand corner - the 200 ohm green setting next to the black sine wave symbol. Touch the probes together to confirm they give 0 ohms first

  2. #22
    Join Date: Feb 2013

    Location: W Lothian

    Posts: 99,005
    I'm Grant.

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    Black to centre hole marked com. Red to right hole marked v ohms etc.. Set dial to the green settings at bottom marked ohms. The second one up looks like continuity. Touching the leads together should go to 0 and if continuity selected(not sure its is) then it will bleep
    Regards,
    Grant .... ؠ ......Don't be such a big girl's blouse

    I've said it before and I'll say it again: democracy simply-doesn't-work
    .... ..... ...... ...... ................... ..... ..... ..... ..... .....
    FIIO K7 BT, M11 PLUS, BTR7, KA5 - OPPO BDP-103D - PANASONIC UB450 - PANASONIC 4K ULTRA HD TV - PIXEL 6 - AVANTREE LR BLUETOOTH - 2* X600 SOUNDCORE - HEADPHONES INCLUDE, FIIO, NURAPHONES', FOCAL, OPPO, BOSE, CAMBRIDGE, BOWER & WILKINS, DEVIALET, MARSHALL, SONY, MITCHELL & JOHNSTON - 2*ZBOOK'S- MERCURY BD ROM, ROON, QOBUZ, TIDAL, PLEX, CYBERLINK, JRIVER - MULTI HDD'S -

    Oh my god! There's nothing wrong with the bidet is there?

    “Nothing discloses real character like the use of power. It is easy for the weak to be gentle. Most people can bear adversity. But if you wish to know what a man really is, give him power. This is the supreme test. It is the glory of Lincoln that, having almost absolute power, he never abused it, except on the side of mercy".

    “You see these dictators on their pedestals, surrounded by the bayonets of their soldiers and the truncheons of their police ... yet in their hearts there is unspoken fear. They are afraid of words and thoughts: words spoken abroad, thoughts stirring at home -- all the more powerful because forbidden -- terrify them. A little mouse of thought appears in the room, and even the mightiest potentates are thrown into panic.”

    "You don't have free will. You have the appearance of free will.”

    “There's a war out there, old friend. A world war. And it's not about who's got the most bullets. It's about who controls the information. What we see and hear, how we work, what we think... it's all about the information!”


    ***SMILE, BE HAPPY***

  3. #23
    Join Date: Aug 2011

    Location: Coventry, England UK

    Posts: 534
    I'm Simon.

    Default

    Right, got that. So when you say touch the earth pin on the plug - is that the wall socket end or the end which plugs into the amp? Can I touch the earth pin on the inside where the power goes into the amp or does it have to be the underside?

  4. #24
    Join Date: Feb 2013

    Location: W Lothian

    Posts: 99,005
    I'm Grant.

    Default

    On plug
    Regards,
    Grant .... ؠ ......Don't be such a big girl's blouse

    I've said it before and I'll say it again: democracy simply-doesn't-work
    .... ..... ...... ...... ................... ..... ..... ..... ..... .....
    FIIO K7 BT, M11 PLUS, BTR7, KA5 - OPPO BDP-103D - PANASONIC UB450 - PANASONIC 4K ULTRA HD TV - PIXEL 6 - AVANTREE LR BLUETOOTH - 2* X600 SOUNDCORE - HEADPHONES INCLUDE, FIIO, NURAPHONES', FOCAL, OPPO, BOSE, CAMBRIDGE, BOWER & WILKINS, DEVIALET, MARSHALL, SONY, MITCHELL & JOHNSTON - 2*ZBOOK'S- MERCURY BD ROM, ROON, QOBUZ, TIDAL, PLEX, CYBERLINK, JRIVER - MULTI HDD'S -

    Oh my god! There's nothing wrong with the bidet is there?

    “Nothing discloses real character like the use of power. It is easy for the weak to be gentle. Most people can bear adversity. But if you wish to know what a man really is, give him power. This is the supreme test. It is the glory of Lincoln that, having almost absolute power, he never abused it, except on the side of mercy".

    “You see these dictators on their pedestals, surrounded by the bayonets of their soldiers and the truncheons of their police ... yet in their hearts there is unspoken fear. They are afraid of words and thoughts: words spoken abroad, thoughts stirring at home -- all the more powerful because forbidden -- terrify them. A little mouse of thought appears in the room, and even the mightiest potentates are thrown into panic.”

    "You don't have free will. You have the appearance of free will.”

    “There's a war out there, old friend. A world war. And it's not about who's got the most bullets. It's about who controls the information. What we see and hear, how we work, what we think... it's all about the information!”


    ***SMILE, BE HAPPY***

  5. #25
    Join Date: Feb 2013

    Location: W Lothian

    Posts: 99,005
    I'm Grant.

    Default

    Dont do it with the power on.
    Regards,
    Grant .... ؠ ......Don't be such a big girl's blouse

    I've said it before and I'll say it again: democracy simply-doesn't-work
    .... ..... ...... ...... ................... ..... ..... ..... ..... .....
    FIIO K7 BT, M11 PLUS, BTR7, KA5 - OPPO BDP-103D - PANASONIC UB450 - PANASONIC 4K ULTRA HD TV - PIXEL 6 - AVANTREE LR BLUETOOTH - 2* X600 SOUNDCORE - HEADPHONES INCLUDE, FIIO, NURAPHONES', FOCAL, OPPO, BOSE, CAMBRIDGE, BOWER & WILKINS, DEVIALET, MARSHALL, SONY, MITCHELL & JOHNSTON - 2*ZBOOK'S- MERCURY BD ROM, ROON, QOBUZ, TIDAL, PLEX, CYBERLINK, JRIVER - MULTI HDD'S -

    Oh my god! There's nothing wrong with the bidet is there?

    “Nothing discloses real character like the use of power. It is easy for the weak to be gentle. Most people can bear adversity. But if you wish to know what a man really is, give him power. This is the supreme test. It is the glory of Lincoln that, having almost absolute power, he never abused it, except on the side of mercy".

    “You see these dictators on their pedestals, surrounded by the bayonets of their soldiers and the truncheons of their police ... yet in their hearts there is unspoken fear. They are afraid of words and thoughts: words spoken abroad, thoughts stirring at home -- all the more powerful because forbidden -- terrify them. A little mouse of thought appears in the room, and even the mightiest potentates are thrown into panic.”

    "You don't have free will. You have the appearance of free will.”

    “There's a war out there, old friend. A world war. And it's not about who's got the most bullets. It's about who controls the information. What we see and hear, how we work, what we think... it's all about the information!”


    ***SMILE, BE HAPPY***

  6. #26
    Join Date: Aug 2009

    Location: Staffordshire, England

    Posts: 37,928
    I'm Martin.

    Default

    Quote Originally Posted by struth View Post
    Dont do it with the power on.
    Sounds like the title of an 'Eighties dance single.
    Current Lash Up:

    TEAC VRDS 701T > Sony TAE1000ESD > Krell KSA50S > JM Labs Focal Electra 926.

  7. #27
    Join Date: Jun 2011

    Location: Skien, Norway

    Posts: 932
    I'm Jostein.

    Default

    Some good input for locating the cause of hum here:

    http://www.psaudio.com/ps_how/how-to-find-and-fix-hum/
    My hifi system:

    Turntable: Technics SL-1200 MKII, Ortofon 2M Bronze cartridge, Mike New bearing, MCRU PSU (c), Oyaide HS-CF headshell, Oyaide MJ-12 TT mat, Vantage Audio Copper mat, Isonoe Isolation Feet, Isodek IF-2 isolation platform, Furutech Monza LP stabilizer, Herbie's Hal-O JR damper Phono Stage: Hagerman Cornet 3 (prototype) Amplifiers: EAR 868L Preamp, Transcription Audio 211 Heaven Power amp, Bob Carver Cherry 180 power amp CD Player: Ear Yoshino Acute Tuner: Magnum Dynalab 90T Speakers: Vandersteen 2CE SigII, Townshend Audio Super Tweeters, Transcription Audio Speakers Cables and stuff: LFD Audio interconnects and speaker cables, Mark Grant G2000HD, BlackCat Electronics, Van Den Hul Clearwater, Black Rhodium mains cables, Black Rhodium mains block, Finite Elements Resonator, Townhsend Stella Speaker stands, Pro Audio Bono hifi rack, Herbie's spike gliders, Herbie's Ultravox and Hal-O tube dampers, Super Black Hole CD mat Record Cleaning Machine: Loricraft PRC4

  8. #28
    Join Date: Aug 2011

    Location: Coventry, England UK

    Posts: 534
    I'm Simon.

    Default

    Quote Originally Posted by struth View Post
    Dont do it with the power on.
    Haha, I'm stupid but not that so, haha.

    Just tried the power amp but got no reading (stayed at .1 which seems the default), reckon I may have to pop the top off or maybe I'm missing where to get a metal contact as the screw I took out didn't seem to give me anything - which also means the wire I tried earlier wasn't effective). I did try a reading from the wall plug earth to the earth hole in the amp end of the cable - which gave me a reading of between 0-20ohm (mostly 0 but it did spike to around 15-20 at times) and the voltmeter buzzed as had it on the right setting for continuity.

    I'll have to continue tomorrow as I must get some sleep - otherwise I'll be falling asleep at work tonight!

  9. #29
    Join Date: Apr 2013

    Location: Granes - Haut Vallee de l'aude - EU

    Posts: 2,831
    I'm Richard.

    Default

    Quote Originally Posted by Simon_LDT View Post
    Haha, I'm stupid but not that so, haha.

    Just tried the power amp but got no reading (stayed at .1 which seems the default), reckon I may have to pop the top off or maybe I'm missing where to get a metal contact as the screw I took out didn't seem to give me anything - which also means the wire I tried earlier wasn't effective). I did try a reading from the wall plug earth to the earth hole in the amp end of the cable - which gave me a reading of between 0-20ohm (mostly 0 but it did spike to around 15-20 at times) and the voltmeter buzzed as had it on the right setting for continuity.


    I'll have to continue tomorrow as I must get some sleep - otherwise I'll be falling asleep at work tonight!

    Get some sleep. When you get back refreshed use your resistance measurement to track up to find the fault. Start with the cables. Earth pin on the plug to earth pin in the iee socket. Then check earth pin on plug to the chassis. On a class 1 device, assuming you have found a bare metal contact point, this should be zero ohms. If its not

    You may not have found a bare chassis connection - not always easy - OR
    If you have found a bare chassis connection and you don't have zero ohms you have a dangerous fault and never mind hum, you needs somebody who knows what they are doing taking a look at it.

    If you can find a good chassis connection on both chassis, where you get zero ohms from chassis to earth pin on the plug, then if you connect the 2 chassis, you should get zero ohms (or very few ohms) between the 2 plug earth pins.

    Best of luck

  10. #30
    Join Date: Feb 2013

    Location: W Lothian

    Posts: 99,005
    I'm Grant.

    Default

    Quote Originally Posted by Simon_LDT View Post
    Haha, I'm stupid but not that so, haha.

    Just tried the power amp but got no reading (stayed at .1 which seems the default), reckon I may have to pop the top off or maybe I'm missing where to get a metal contact as the screw I took out didn't seem to give me anything - which also means the wire I tried earlier wasn't effective). I did try a reading from the wall plug earth to the earth hole in the amp end of the cable - which gave me a reading of between 0-20ohm (mostly 0 but it did spike to around 15-20 at times) and the voltmeter buzzed as had it on the right setting for continuity.

    I'll have to continue tomorrow as I must get some sleep - otherwise I'll be falling asleep at work tonight!
    Sorry...but its been done lol...
    Regards,
    Grant .... ؠ ......Don't be such a big girl's blouse

    I've said it before and I'll say it again: democracy simply-doesn't-work
    .... ..... ...... ...... ................... ..... ..... ..... ..... .....
    FIIO K7 BT, M11 PLUS, BTR7, KA5 - OPPO BDP-103D - PANASONIC UB450 - PANASONIC 4K ULTRA HD TV - PIXEL 6 - AVANTREE LR BLUETOOTH - 2* X600 SOUNDCORE - HEADPHONES INCLUDE, FIIO, NURAPHONES', FOCAL, OPPO, BOSE, CAMBRIDGE, BOWER & WILKINS, DEVIALET, MARSHALL, SONY, MITCHELL & JOHNSTON - 2*ZBOOK'S- MERCURY BD ROM, ROON, QOBUZ, TIDAL, PLEX, CYBERLINK, JRIVER - MULTI HDD'S -

    Oh my god! There's nothing wrong with the bidet is there?

    “Nothing discloses real character like the use of power. It is easy for the weak to be gentle. Most people can bear adversity. But if you wish to know what a man really is, give him power. This is the supreme test. It is the glory of Lincoln that, having almost absolute power, he never abused it, except on the side of mercy".

    “You see these dictators on their pedestals, surrounded by the bayonets of their soldiers and the truncheons of their police ... yet in their hearts there is unspoken fear. They are afraid of words and thoughts: words spoken abroad, thoughts stirring at home -- all the more powerful because forbidden -- terrify them. A little mouse of thought appears in the room, and even the mightiest potentates are thrown into panic.”

    "You don't have free will. You have the appearance of free will.”

    “There's a war out there, old friend. A world war. And it's not about who's got the most bullets. It's about who controls the information. What we see and hear, how we work, what we think... it's all about the information!”


    ***SMILE, BE HAPPY***

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