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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

    Location: W Lothian

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    I'm Grant.

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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

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  3. #23
    Join Date: Sep 2013

    Location: North Island New Zealand

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    I'm Chris.

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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
    Join Date: Mar 2008

    Location: Dunfermline, Scotland, UK

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    I'm inthescottishmafia.

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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
    Join Date: Jan 2019

    Location: Cambridgeshire, United Kingdom

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    I'm Russell.

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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

    Location: Dunfermline, Scotland, UK

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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

    Location: W Lothian

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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

    I've said it before and I'll say it again: democracy simply-doesn't-work
    .... ..... ...... ...... ................... ..... ..... ..... ..... .....
    OPPO BDP-103D DARBEE - JBE SERIES 3/B&O SP1/PROJECT PHONOBOX DS2 USB - QUAD VENA 2 - IFI PURIFIER 2/TWIN PRO MONOBLOCK POWER AMPLIFIERS - LEAF HD BLUETOOTH - OPPO PM-3 PLANAR, SONY H900 & NURAPHONE HEADPHONES - ZBOOK/ IFI SILENCER/WIN10 PRO/AUDIRVANA 3 PLUS/TIDAL - SMSL M6 DAC & IFI SILENCER - RPI 3+, DIGIONE HAT/VOLUMIO2 - FULL RANGE TWIN TELEFUNKEN SPEAKERS - CABLE INC CHORD, MOGAMI, SUPRA & WIREWORLD

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  8. #28
    Join Date: May 2012

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    Have you looked closely at the speaker cables / terminations ?
    Music , fills the gaps between silence !

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  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.
    "when common sense, logic and plausibility are excluded. All that remain are foolishness and lies"

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