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Thread: Chasing ground loops and hum

  1. #1
    Administrator Robh3606's Avatar
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    Chasing ground loops and hum

    After all these years I finally had to change out one of my active crossovers in my HT/Stereo set up. I can't tell you how many times I tried redoing grounds/lifting grounds over the last month trying to figure out where a persistent hum that developed was coming from. I had to physically move the rack and cable harness and gave up cable which complicated things. Hum started shortly after. No matter what it just wasn't going away.

    Well to make a long story short it was internal to my M553 crossover. Moving things was just coincidental to the real cause. Looking for a replacement I found DBX 234XS which was a direct replacement in the rack no rerouting of no cabling required. Thank god!

    If you ever face a similar circumstance check the individual components not just the cables and grounds. Would have saved me lots of time. I found it by simply powering up the M553 inputs off and turning on the amp to my E-145's. Hummmmmmmmmm!

    The DBX is supper quiet so all is well!!

    Rob
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    Administrator Mr. Widget's Avatar
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    Darn vintage electronics.

    So you stayed with an analog crossover? Iím pretty sure my next crossover will be a DSP for better SN and flexibility.


    Widget

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    Administrator Robh3606's Avatar
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    Quote Originally Posted by Mr. Widget View Post
    Darn vintage electronics.

    So you stayed with an analog crossover? Iím pretty sure my next crossover will be a DSP for better SN and flexibility.


    Widget
    Hello Widget

    If I was staring from scratch I agree. Firm believer in do not fix what is not broken. I have had that same electronics set-up for well over a decade and it has served me well. This old warhorse sums flat and sounds great so no complaints.

    It's a vintage rack for sure and I have been very lucky nothing has "broken" until now. Here is the whole rack.

    BX-63A for the B380 clones with the EQ for them underneath a 1/6 octave analog SPP-SWEQ 16-80Hz

    M552 feeding the DBX then the URIE 539 1/3 octave analog 40-16K

    Crown PS-200 for low, mid and high PS-400 for the B 380 subs.

    The Berhringer 8024 is RTA only and the Crown 2002 is HT subs.

    One of these days I will dabble in a digital but so far I have resisted the "dark side". I was looking at the Drive Rack but it didn't make sense to cascade a digital with an analog.

    It all works I am happy!

    Rob
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  4. #4
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    The M553 may well be old enough that the electrolytic capacitors may be going bad. Power supply filter caps going bad could very easily result in increased 60hz hum.
    Quote Originally Posted by Robh3606 View Post
    ...Well to make a long story short it was internal to my M553 crossover. Moving things was just coincidental to the real cause. Looking for a replacement I found DBX 234XS which was a direct replacement in the rack no rerouting of no cabling required. Thank god! If you ever face a similar circumstance check the individual components not just the cables and grounds. Would have saved me lots of time. I found it by simply powering up the M553 inputs off and turning on the amp to my E-145's. Hummmmmmmmmm! The DBX is supper quiet so all is well!! Rob

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    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Robh3606 View Post
    It's a vintage rack for sure and I have been very lucky nothing has "broken" until now. Here is the whole rack.
    Nice looking rack... love the vintage look.


    Widget

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    Quote Originally Posted by Robh3606 View Post
    If you ever face a similar circumstance check the individual components not just the cables and grounds. Would have saved me lots of time.
    Agree. Also, an often-overlooked ground loop path can occur via your cable service, through your TV if connected to your audio system. Had that experience. I just unplugged it as I didn't have cable TV any longer. Not sure what the fix is, could be a direct ground from the TV cable to the electrical panel ground, or perhaps some sort of in-line filter.

    This must be the week for analog crossover failures. I had one too, didn't manifest itself as a ground loop hum, but a wonky sound through the speakers, and occasionally a rapid thumping. Diagnosed it by starting from the speakers and working backwards through the system.

    I have a spare analog unit but I will be in the process of moving eventually and already had plans to convert this system to digital DSP.

    It may be just me, but I expect this stuff to last forever based on what I pay for it...

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