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Thread: New set up annoying buzz / hum I can't get to the bottom of......

  1. #21
    Join Date: Jan 2019

    Location: Cambridgeshire, United Kingdom

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    I'm Russell.

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    Quote Originally Posted by Light Dependant Resistor View Post
    The usual cause of hum like this in a unbalanced audio system is a cable with a ground connection missing or broken - like a RCA cable looking OK externally but actually having a
    broken connection for its ground. Suggest disconnect input cables to power amp... does hum disappear ? If Yes then fault is a input cable.requiring repair or replacement.

    Opto coupling with a LDR attenuator enables total silence for audio attenuation- which is a amazing feature of LDR's that other preamps cannot match.
    Thanks Chris & although the hum does disappear when no cables are connected to the input, just speaker cables to the speakers, as soon as I attach any cables (tried about 6 different ones) , the hum comes back so don't think it's cable related in this instance.

  2. #22
    Join Date: Feb 2013

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    maybe they are picking up electrical/radio interference?.. ive seen this before too and its difficult to find.. can come from mains leads near the cables. I had one am that was very bad for this.
    as i say, if amp is checked over, then it can be looked at after... if you have another system to try amp in, then see if you get the same happening.
    Regards,
    Grant .... ؠ ......Don't be such a big girl's blouse

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    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".

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  3. #23
    Join Date: Sep 2013

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    Quote Originally Posted by Weeman1973 View Post
    Thanks Chris & although the hum does disappear when no cables are connected to the input, just speaker cables to the speakers, as soon as I attach any cables (tried about 6 different ones) , the hum comes back so don't think it's cable related in this instance.
    But is indicating there is at least one cable missing its ground upward from the power amp. You just need to find which one.

  4. #24
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    If there is no hum with all inputs disconnected then the problem does not lie with the amp, unless you still get the cone movement with the volume control turning which will be a separate issue if so.
    “Music has always been a matter of energy to me, a question of fuel. Sentimental people call it inspiration, but what they really mean is fuel. I have always needed fuel. I am a serious consumer. On some nights I still believe that a car with the gas needle on empty can run about fifty more miles if you have the right music very loud on the radio”

    Hunter S Thompson

  5. #25
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    Quote Originally Posted by Ali Tait View Post
    If there is no hum with all inputs disconnected then the problem does not lie with the amp, unless you still get the cone movement with the volume control turning which will be a separate issue if so.
    That's what I thought as well, however whichever cable I use to connect the pre to the power enhances the hum (even just adding cables to the input of the Power amp without connecting the other end to the pre amp)

    The pre works silently with another power amp (SS one) which is why I'm ruling out the pre amp.

    Can't tell if the cone flapping is power or pre related as obviously can only turn volume up & down once the pre is connected to the power then the power connected to the speakers.

  6. #26
    Join Date: Mar 2008

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    ...which proves the cables are ok lol, so it’s a problem with pre when it’s connected to that amp.

    Does one of your other amps have a pre out so you can try that as the preamp into your main amp.
    “Music has always been a matter of energy to me, a question of fuel. Sentimental people call it inspiration, but what they really mean is fuel. I have always needed fuel. I am a serious consumer. On some nights I still believe that a car with the gas needle on empty can run about fifty more miles if you have the right music very loud on the radio”

    Hunter S Thompson

  7. #27
    Join Date: Feb 2013

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    I thought it was still humming by itself?
    Maybe at cross porpoises here so will drop out. Ali will tell u all you need to know
    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***

  8. #28
    Audio Al is offline Pishanto Specialist & Super-Daftee
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    Have you looked closely at the speaker cables / terminations ?
    [

  9. #29
    Join Date: Nov 2008

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    Quote Originally Posted by Weeman1973 View Post
    I've now uploaded some video of the hum & cones flapping on both my La Scala's & Naim Speakers (easier to see on the Naim's):

    https://www.youtube.com/watch?v=9JBn8A8WFzU

    https://www.youtube.com/watch?v=j9DtfjsJziM
    The tone of the noise is around about G, which roughly translates to 49Hz ish. It could be the octave harmonic I'm picking up more, so 100Hz ish.
    It's mains frequency noise.
    Chris



    Common sense isn't anymore!

  10. #30
    Join Date: Apr 2012

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    I'm Geoff.

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    Is the signal neg common with the amp chassis/case? It could be worth running a wire between the metal casework of the power amp to the case of the pre-amp to see what happens. It may go quiet, get worse or do nothing.
    It is impossible for anything digital to sound analogue, because it isn't analogue!

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